golang array assignment

• Data Types in Go
• Go Keywords
• Go Control Flow
• Go Functions
• GoLang Structures
• GoLang Arrays
• GoLang Strings
• GoLang Pointers
• GoLang Interface
• GoLang Concurrency
• Go Programming Language (Introduction)
• How to Install Go on Windows?
• How to Install Golang on MacOS?
• Hello World in Golang

Fundamentals

• Identifiers in Go Language
• Go Variables
• Constants- Go Language
• Go Operators

Control Statements

• Go Decision Making (if, if-else, Nested-if, if-else-if)
• Loops in Go Language
• Switch Statement in Go

Functions & Methods

• Functions in Go Language
• Variadic Functions in Go
• Anonymous function in Go Language
• main and init function in Golang
• What is Blank Identifier(underscore) in Golang?
• Defer Keyword in Golang
• Methods in Golang
• Structures in Golang
• Nested Structure in Golang
• Anonymous Structure and Field in Golang

Arrays in Go

• How to Copy an Array into Another Array in Golang?
• How to pass an Array to a Function in Golang?
• Slices in Golang
• Slice Composite Literal in Go
• How to sort a slice of ints in Golang?
• How to trim a slice of bytes in Golang?
• How to split a slice of bytes in Golang?
• Strings in Golang
• How to Trim a String in Golang?
• How to Split a String in Golang?
• Different ways to compare Strings in Golang
• Pointers in Golang
• Passing Pointers to a Function in Go
• Pointer to a Struct in Golang
• Go Pointer to Pointer (Double Pointer)
• Comparing Pointers in Golang

Concurrency

• Goroutines - Concurrency in Golang
• Select Statement in Go Language
• Multiple Goroutines
• Channel in Golang
• Unidirectional Channel in Golang

Arrays in Golang or Go programming language is much similar to other programming languages. In the program, sometimes we need to store a collection of data of the same type, like a list of student marks. Such type of collection is stored in a program using an Array. An array is a fixed-length sequence that is used to store homogeneous elements in the memory. Due to their fixed length array are not much popular like Slice in Go language. In an array, you are allowed to store zero or more than zero elements in it. The elements of the array are indexed by using the [] index operator with their zero-based position, which means the index of the first element is array[0] and the index of the last element is array[len(array)-1] . 

Creating and accessing an Array

In Go language, arrays are created in two different ways:

Using var keyword: In Go language, an array is created using the var keyword of a particular type with name, size, and elements. Syntax:

Important Points:

In Go language, arrays are mutable, so that you can use array[index] syntax to the left-hand side of the assignment to set the elements of the array at the given index.

• You can access the elements of the array by using the index value or by using for loop.
• In Go language, the array type is one-dimensional.
• The length of the array is fixed and unchangeable.
• You are allowed to store duplicate elements in an array.

Approach 1: Using shorthand declaration:

In Go language, arrays can also declare using shorthand declaration. It is more flexible than the above declaration. 

Example:  

Multi-Dimensional Array

As we already know that arrays are 1-D but you are allowed to create a multi-dimensional array. Multi-Dimensional arrays are the arrays of arrays of the same type . In Go language, you can create a multi-dimensional array using the following syntax:

You can create a multidimensional array using Var keyword or using shorthand declaration as shown in the below example. 

Note: In a multi-dimension array, if a cell is not initialized with some value by the user, then it will initialize with zero by the compiler automatically. There is no uninitialized concept in the Golang. 

Important Observations About Array

In an array, if an array does not initialize explicitly, then the default value of this array is 0 . 

In an array, you can find the length of the array using len() method as shown below: 

In an array, if ellipsis ‘‘…’’ become visible at the place of length, then the length of the array is determined by the initialized elements. As shown in the below example: 

In an array, you are allowed to iterate over the range of the elements of the array . As shown in the below example: 

In Go language, an array is of value type not of reference type . So when the array is assigned to a new variable, then the changes made in the new variable do not affect the original array. As shown in the below example: Example:  

In an array, if the element type of the array is comparable, then the array type is also comparable. So we can directly compare two arrays using == operator . As shown in the below example: 

Please Login to comment...

Similar reads.

• Golang-Arrays
• Go Language
• Google Releases ‘Prompting Guide’ With Tips For Gemini In Workspace
• Google Cloud Next 24 | Gmail Voice Input, Gemini for Google Chat, Meet ‘Translate for me,’ & More
• 10 Best Viber Alternatives for Better Communication
• 12 Best Database Management Software in 2024
• 30 OOPs Interview Questions and Answers (2024)

Improve your Coding Skills with Practice

What kind of Experience do you want to share?

• PyQt5 ebook
• Tkinter ebook
• SQLite Python
• wxPython ebook
• Windows API ebook
• Java Swing ebook
• Java games ebook
• MySQL Java ebook

last modified April 11, 2024

In this article we show how to work with arrays in Golang.

An array is a collection of elements of a single data type. An array holds a fixed number of elements and it cannot grow or shrink.

Elements of an array are accessed through indexes. The first index is 0. By default, empty arrays are initialized with zero values (0, 0.0, false, or "").

The len function returns the length of the array.

We use Go version 1.22.2.

Declaring array

We declare an array of length n and having type T .

Here we declare an array of five integers.

This is a shorthand declaration and initialization of a Go array.

Array initialization

The following example shows how to initialize an array in Go.

In the code example, we declare an array of integers; the array can hold two elements.

The [2]int is the whole type, including the size number. At the beginning, the array contains 0s.

We assign two values to the array.

Array literal

Golang has array literals; we can specify the elements of the array between {} brackets.

In the code example, we define two arrays with array literals.

The first array has five elements; all elements are initialized between {} brackets.

Here we provide only three out of five elements; the rest are initialized to 0.

In the array literal, we can provide the index of the element.

In the code example, we initialize an array with array literal. The values are given their index; the rest of the array elements are given 0 value.

Infering array length

Go can infer the array length when using array literals. For this, we use the ellipses ... operator.

In the code example, we use the ... in the array declaration. This tells Go to infer the length of the array from the provided array literal.

To extract type information in Go, we use the reflect package.

The a is an array, while the b is a slice.

Array length

The length of the array is determined with the len function.

In the code example, we define an array of strings. We print the number of words in the array.

Array indexing

Arrays are accessed with their index.

In the code example, we work with an array of words.

We declare an array of strings, having five elements.

We put five words into the array.

We print the first and the second element of the array.

We print the whole array.

We can use the : colon character to retrieve a portion of the array.

The example prints portions of the defined array.

Array iteration

With for loops, we can iterate over array elements in Go.

The example uses three for loop forms to iterate over an array of words.

Go array is value type

Unlike in other languages, array is a value type in Go. This means that when we assign an array to a new variable or pass an array to a function, the entire array is copied.

In the code example, we define an array and assign the array to a new variable. The changes made through the second variable will not affect the original array.

The original array is unchanged.

Multidimensional arrays

We can create multi-dimensional arrays in Go. We need additional pairs of square and curly brackets for additional array dimension.

We work with two-dimensional arrays of integers.

There are two nested arrays in the outer array.

In the second case, the array is initialized to random values. We use two for loops.

In the following example, we create a three-dimensional array.

We need three pairs of [] and {} brackets.

Partial assignment

An array can be partially assigned.

The type and the size of the arrays must match. The elements for which there is no value will be initialized to zero.

The last two elements are initialized to 0.

In this article we have worked with arrays in Golang.

My name is Jan Bodnar and I am a passionate programmer with many years of programming experience. I have been writing programming articles since 2007. So far, I have written over 1400 articles and 8 e-books. I have over eight years of experience in teaching programming.

List all Go tutorials .

Golang Tutorial

Golang reference, beego framework, arrays in golang explained: essential guide to basics and beyond with examples.

In this tutorial you'll learn how to store multiple values in a single variable in Golang

Introduction

An array is a data structure that consists of a collection of elements of a single type or simply you can say a special variable, which can hold more than one value at a time. The values an array holds are called its elements or items . An array holds a specific number of elements, and it cannot grow or shrink. Different data types can be handled as elements in arrays such as Int , String , Boolean , and others. The index of the first element of any dimension of an array is 0, the index of the second element of any array dimension is 1, and so on.

Declaring an Array

array array

Assign and Access Values

You access or assign the array elements by referring to the index number. The index is specified in square brackets.

Initializing an Array with an Array Literal

You can initialize an array with pre-defined values using an array literal. An array literal have the number of elements it will hold in square brackets, followed by the type of its elements. This is followed by a list of initial values separated by commas of each element inside the curly braces.

Initializing an Array with ellipses...

When we use ... instead of specifying the length. The compiler can identify the length of an array, based on the elements specified in the array declaration.

Initializing Values for Specific Elements

When an array declare using an array literal, values can be initialize for specific elements.

Loop Through an Indexed Array

You can loop through an array elements by using a for loop.

You can create copy of an array, by assigning an array to a new variable either by value or reference.

Check if Element Exists

This Go program checks whether an element exists in an array or not. The program takes an array and an item as input arguments, and it returns a boolean value indicating whether the item exists in the array or not.

The program uses the reflect package in Go to determine the kind of data type of the input array. If the input is not an array, the program panics with an "Invalid data-type" error.

The itemExists function in the program uses a loop to iterate through the elements of the input array. It uses the Index method of the reflect.Value type to access the value of the array element at each index. It then compares the value with the input item using the Interface method of reflect.Value. If a match is found, the function returns true, indicating that the item exists in the array. If no match is found, the function returns false.

In the main function, the program creates an array of strings and calls the itemExists function twice to check whether the items "Canada" and "Africa" exist in the array. The program prints the return values of the function calls, which are either true or false , depending on whether the items exist in the array or not.

Filter Array Elements

You can filter array element using : as shown below

Most Helpful This Week

Mastering Arrays in Go Programming

In Go, or Golang, arrays are a fundamental data structure that allows you to store multiple values of the same type in a single variable. Understanding arrays and their nuances is crucial for Go programmers, as they form the basis of more complex data structures like slices. This blog post will provide a comprehensive overview of arrays in Go, including their declaration, initialization, manipulation, and common use cases.

What are Arrays in Go?

An array is a numbered sequence of elements of a specific length and type. The size of an array is fixed, and the length is part of the array's type. This means arrays of different sizes are considered to be of different types.

Declaration of Arrays

Arrays are declared by specifying the type of the elements and the number of elements they will hold.

This line declares an array myArray that can hold five integers.

Initializing Arrays

Arrays can be initialized using an array literal:

You can also initialize an array with default values:

... Operator in Array Initialization

Go provides the ... operator to let the compiler determine the array length based on the number of initializers:

In this case, myArray is an array of five integers.

Accessing and Modifying Array Elements

Elements in an array can be accessed using their index, starting from zero:

Iterating Over Arrays

You can iterate over an array using a for loop or a for loop with the range keyword:

Arrays Are Value Types

In Go, arrays are value types, not reference types. This means that when you assign an array to another variable, a copy of the entire array is made.

Modifying copy does not change original .

Limitations of Arrays

While arrays are useful, they have limitations:

• Fixed Size: The size of an array cannot be changed. This can be restrictive when the number of elements is not known in advance or can change.
• Value Type Semantics: Copying large arrays can be inefficient due to the value-type behavior.

Slices: A More Flexible Alternative

Due to the limitations of arrays, slices are often used in Go as a more flexible alternative. Slices are built on top of arrays but provide more flexibility, including the ability to resize.

Arrays in Go are a basic but powerful data structure. They provide a way to store a fixed-size sequential collection of elements of the same type. While arrays have their limitations, mainly around their fixed size and value-type nature, they lay the groundwork for understanding slices, a more dynamic and flexible data structure widely used in Go programming. Understanding arrays is a stepping stone to mastering slices and effectively handling collections of data in Go.

Arrays in Golang

Arrays are consecutive storage of the same data-type. In this post, we will see how arrays work in Golang.

Declaration of an Array

To declare an array in Go we first give its name, then size, then type as shown below.

Initialization of an Array

Let’s see how to initialize an array. If we don’t initialize it will take zero-value for all values.

Here zero-value for a string is an empty string “”.

Array access by index

Array elements can be accessed by their index as shown below.

Iterating over Array Elements

To iterate we simple loop over the entire array. We here use a specific keyword called range which helps make this task a lot easier.

Multi-Dimensional Arrays in Go

Multi-Dimensional arrays can be used in Go just like any other array. Below is an example.

Working with Arrays in Golang

An array is a fixed-size collection of elements of the same type. The elements of the array are stored sequentially and can be accessed using their index .

Declaring an Array in Golang

You can declare an array of length n and type T like so -

For example, here is how you can declare an array of 10 integers -

Now let’s see a complete example -

By default, all the array elements are initialized with the zero value of the corresponding array type.

For example, if we declare an integer array, all the elements will be initialized with 0 . If we declare a string array, all the elements will be initialized with an empty string "" , and so on.

Accessing array elements by their index

The elements of an array are stored sequentially and can be accessed by their index . The index starts from zero and ends at length - 1 .

In the above example, Since we didn’t assign any value to x[2] , it has the value 0 (The zero value for integers).

Initializing an array using an array literal

You can declare and initialize an array at the same time like this -

The expression on the right-hand side of the above statement is called an array literal.

Note that we do not need to specify the type of the variable a as in var a [5]int , because the compiler can automatically infer the type from the expression on the right hand side.

You can also use Golang’s short variable declaration for declaring and initializing an array. The above array declaration can also be written as below inside any function -

Here is a complete example -

Letting Go compiler infer the length of the array

You can also omit the size declaration from the initialization expression of the array, and let the compiler count the number of elements for you -

Exploring more about Golang arrays

Array’s length is part of its type

The length of an array is part of its type. So the array a[5]int and a[10]int are completely distinct types, and you cannot assign one to the other.

This also means that you cannot resize an array, because resizing an array would mean changing its type, and you cannot change the type of a variable in Golang.

Arrays in Golang are value types

Arrays in Golang are value types unlike other languages like C, C++, and Java where arrays are reference types.

This means that when you assign an array to a new variable or pass an array to a function, the entire array is copied. So if you make any changes to this copied array, the original array won’t be affected and will remain unchanged.

Here is an example -

Iterating over an array in Golang

You can use the for loop to iterate over an array like so -

The len() function in the above example is used to find the length of the array.

Let’s see another example. In the example below, we find the sum of all the elements of the array by iterating over the array, and adding the elements one by one to the variable sum -

Iterating over an array using range

Golang provides a more powerful form of for loop using the range operator. Here is how you can use the range operator with for loop to iterate over an array -

Let’s now write the same sum example that we wrote with normal for loop using range form of the for loop -

When you run the above program, it’ll generate an error like this -

Go compiler doesn’t allow creating variables that are never used. You can fix this by using an _ (underscore) in place of index -

The underscore ( _ ) is used to tell the compiler that we don’t need this variable. The above program now runs successfully and outputs the sum of the array -

Multidimensional arrays in Golang

All the arrays that we created so far in this post are one dimensional. You can also create multi-dimensional arrays in Golang.

The following example demonstrates how to create multidimensional arrays -

Arrays are useful but a bit inflexible due to the limitation caused by their fixed size. And this is why Go provides another data structure called Slice that builds on top of arrays and provides all the flexibility that we need. In the next article, we’ll learn about Slices.

Next Article: Introduction to Slices in Golang

Code Samples: github.com/callicoder/golang-tutorials

Share on social media

Arrays are essentially storage spaces that can be filled with as much data as one would like. Variables, unlike arrays, can only contain one piece of data. Now there are some caveats. For instance, an array is syntactically created using one data type, just like variables. Yet, an array grants ease of access and far more capabilities when considering large/vast amounts of data compared to a variable(single storage space/value).

A array in golang has fixed size similar to C and C++ that we give while we define it. We can't change the size of the array dynamically while the program is running.

Arrays in golang are defined using the syntax,

Arrays in golang are 0 indexed i.e. the index starts from 0. Let's make some arrays using the syntax given above

An alternative syntax to the creation of arrays in golang is:

In order to access members of an array, reference the storage space's address or number you used to create it.

Create two arrays, one a string array, the other a int array. Assign the string array three storage spaces which contain the phrase hello world. Assign the int array three storage spaces which contain the values 1, 2, and 3. Finally, print the last items of each array.

Arrays in Go

In Go, an array is used to store multiple values of the same data type in a single variable. It can also be described as a numbered sequence of elements of a specific length.

An array's length is part of its type, so arrays are of fixed size and cannot be resized.

Arrays can be declared in two ways:

• Using var keyword
• Using the shorthand declaration :=

Array Declaration using var Keyword

In Go, an array can be declared using the var keyword with an array name, length, and data type.

The following declares an empty array. A variable named nums as an array of five elements of int type. Since we have not assigned any values, so values will be the default value of int type which is 0.

The following declares and initialize arrays using the var keyword.

In the above example, oddnums is declared and initialized with five elements. [5]int specifies the length of an array.

The cities array initialized with inferred lengths by using using ... , without specific length.

Declare Array Using Shorthand Declaration

In Go, you can use := to declare an array.

In the following example, array2 are declared using the shorthand declarations.

Array Initialization

In Go, an array can be initialized, partially initialized, or not initialized. If an array is not initialized, the elements of the array will take the default value of the array data type. For int, the default is 0 and for string it is "".

Specific elements in an array can be initialized as shown below:

In the above example, 1:6 means, 1st index (second element) will be 6, and 2:7 means 2nd index (third element) will be 7, and rest will be default values of int type, which is 0.

Array Length

The length (or size) of an array denotes the number of elements it can contain. The length of an array is always remain fixed and cannot be changed. If you need to increase or decrease the length then you should either create a new array or create a slice. The len() function returns the length of the specified array.

Accessing Array Elements

The values in the array are called elements. Each element will have an index. The first element's index is 0 and the second element's index is 1 and so on. The square bracket [] is used to specify the index of an element. For example, array[2] will return the third element from the array.

Note that trying to access elements out of index range will throw an error. It is recommended to check array length before accessing.

Update Array Elements

The values of an array can be changed by using the element's index as shown in the following example.

Loop through an Array

You can loop through the elements of an array using the for loop and the len() method.

.NET Tutorials

Database tutorials, javascript tutorials, programming tutorials.

golang arrays can hold multiple values. The minimum elements of an array is zero, but they usually have two or more. Each element in an array has a unique index.

The index starts at zero (0). That means to access the first element of an array, you need to use the zeroth index.

Arrays in golang

Introduction to arrays.

An array is a set of numbered and length-fixed data item sequences that have the same unique type

This type can be any primitive type such as:

• custom type

The array length must be a constant expression and must be a non-negative integer.

An array in the Go language is a type of value (not a pointer to the first element in C/C++), so it can be created by new() :

The array element can be read (or modified) by an index (position), the index starts from 0, the first element index is 0, the second index is 1, and so on.

Note The array starts at 0 in many programming languages, including Golang, C++, C, C# and Python

The number of elements, also known as length or array size, must be fixed and given when the array is declared (need to know the array length to allocate memory at compile time); the array length is up to 2 Gb.

If each element is an integer value, all elements are automatically initialized to the default value of 0 when the array is declared .

The method of traversing an array can either be a condition loop or a for-range can be used.Both of these structures are equally applicable to Slices.

Here is an array of non-fixed length that is determined by the number of elements specified at initialization time.

Several assignment modes:

The program below is an example of an array loop in golang. The array we define has several elements. We print the first item with the zeroth index.

Upon running this program it will output the first (1) and second (2) element of the array. They are referenced by the zeroth and first index. In short: computers start counting from 0.

This program will output:

The index should not be larger than the array, that could throw an error or unexpected results.

Video tutorial

Video below

• Create an array with the number 0 to 10
• Create an array of strings with names

Download Answers

Popular Tutorials

Popular examples, learn python interactively, go introduction.

• Golang Getting Started
• Go Variables
• Go Data Types
• Go Print Statement
• Go Take Input
• Go Comments
• Go Operators
• Go Type Casting

Go Flow Control

• Go Boolean Expression
• Go if...else

Go for Loop

• Go while Loop
• Go break and continue

Go Data Structures

• Go Functions
• Go Variable Scope
• Go Recursion
• Go Anonymous Function
• Go Packages

Go Pointers & Interface

• Go Pointers
• Go Pointers and Functions
• Go Pointers to Struct
• Go Interface
• Go Empty Interface
• Go Type Assertions

Go Additional Topics

• Go defer, panic, and recover

Go Tutorials

An array is a collection of similar types of data. For example,

Suppose we need to record the age of 5 students. Instead of creating 5 separate variables, we can simply create an array.

• Creating an array in Go

Here is a syntax to declare an array in Golang.

Here, the size represents the length of an array. The list of elements of the array goes inside {} .

For example,

In the above example, we have created an array named arrayOfInteger . The int specifies that the array arrayOfIntegers can only store integers.

Other ways to declare a Go array

An array can also be declared without specifying its size. The syntax to declare an array of undefined size is:

In the above example, we have created an array named arrayOfString with an undefined size [...] .

Note: Here, if [] is left empty, it becomes a slice. So [...] is a must if we want an undefined size array.

Arrays can also be created using the shorthand notation := . For example,

In the above program, we have replaced the traditional syntax of creating an array with a shorthand notation ( := ).

• Accessing array elements in Golang

In Go, each element in an array is associated with a number. The number is known as an array index .

We can access elements of an array using the index number (0, 1, 2 …) . For example,

In the above example, we have created an array named languages .

Here, we can see each array element is associated with the index number. And, we have used the index number to access the elements.

Note: The array index always starts with 0 . Hence, the first element of an array is present at index 0 , not 1 .

• Initialize an Array in Golang

We can also use index numbers to initialize an array. For example,

Here, we have initialized an array arrayOfIntegers using the index number. The arrayOfIntegers[0] = 5 represents that index 0 of arrayOfIntegers holds the value 5 , index 1 holds value 10 and so on.

Initialize specific elements of an array

In Golang, we can also initialize the specific element of the array during the declaration. For example,

Here, we have initialized the element at index 0 and 3 with values 7 and 9 respectively.

In this case, all other indexes are automatically initialized with value 0 (default value of integer).

• Changing the array element in Go

To change an array element, we can simply reassign a new value to the specific index. For example,

Here, we have reassigned a new value to index 2 to change the array element from "Cloudy" to "Stromy" .

• Find the length of an Array in Go

In Golang, we can use the len() function to find the number of elements present inside the array. For example,

Here, we have used len() to find the length of an array arrayOfIntegers .

• Looping through an array in Go

In Go, we can also loop through each element of the array. For example,

Here, len() function returns the size of an array. The size of an array age is 3 here, so the for loop iterates 3 times; until all 3 elements are printed.

• Multidimensional array in Golang

Arrays we have mentioned till now are called one-dimensional arrays. However, we can declare multidimensional arrays in Golang.

A multidimensional array is an array of arrays. That is, each element of a multidimensional array is an array itself. For example,

Here, we have created a multidimensional array arrayInteger with 2 rows and 2 columns.

A multidimensional array can be treated like a matrix like this

Table of Contents

• Introduction

Sorry about that.

Related Tutorials

Programming

Arrays and Slices

Welcome to the part 11 of Golang tutorial series . In this tutorial, we will learn about Arrays and Slices in Go.

An array is a collection of elements that belong to the same type. For example, the collection of integers 5, 8, 9, 79, 76 forms an array. Mixing values of different types, for example, an array that contains both strings and integers is not allowed in Go.

Declaration

An array belongs to type [n]T . n denotes the number of elements in an array and T represents the type of each element. The number of elements n is also a part of the type(We will discuss this in more detail shortly.)

There are different ways to declare arrays. Let’s look at them one by one.

Run in playground

var a [3]int declares an integer array of length 3. All elements in an array are automatically assigned the zero value of the array type . In this case a is an integer array and hence all elements of a are assigned to 0 , the zero value of int. Running the above program will print

The index of an array starts from 0 and ends at length - 1 . Let’s assign some values to the above array.

a[0] assigns value to the first element of the array. The program will print

Let’s create the same array using the short hand declaration .

The program above will print the same output

It is not necessary that all elements in an array have to be assigned a value during short hand declaration.

In the above program in line no. 8 a := [3]int{12} declares an array of length 3 but is provided with only one value 12 . The remaining 2 elements are assigned 0 automatically. This program will print

You can even ignore the length of the array in the declaration and replace it with ... and let the compiler find the length for you. This is done in the following program.

The size of the array is a part of the type. Hence [5]int and [25]int are distinct types. Because of this, arrays cannot be resized. Don’t worry about this restriction since slices exist to overcome this.

In line no. 6 of the program above, we are trying to assign a variable of type [3]int to a variable of type [5]int which is not allowed and hence the compiler will print the following error

Arrays are value types

Arrays in Go are value types and not reference types. This means that when they are assigned to a new variable, a copy of the original array is assigned to the new variable. If changes are made to the new variable, it will not be reflected in the original array.

In the above program in line no. 7, a copy of a is assigned to b . In line no. 8, the first element of b is changed to Singapore . This will not reflect in the original array a . The program will print,

Similarly when arrays are passed to functions as parameters, they are passed by value and the original array is unchanged.

In the above program in line no. 13, the array num is actually passed by value to the function changeLocal and hence will not change because of the function call. This program will print,

Length of an array

The length of the array is found by passing the array as parameter to the len function.

The output of the above program is

Iterating arrays using range

The for loop can be used to iterate over elements of an array.

The above program uses a for loop to iterate over the elements of the array starting from index 0 to length of the array - 1 . This program works and will print,

Go provides a better and concise way to iterate over an array by using the range form of the for loop. range returns both the index and the value at that index. Let’s rewrite the above code using range. We will also find the sum of all elements of the array.

line no. 8 for i, v := range a of the above program is the range form of the for loop. It will return both the index and the value at that index. We print the values and also calculate the sum of all elements of the array a . The output of the program is,

In case you want only the value and want to ignore the index, you can do this by replacing the index with the _ blank identifier.

The above for loop ignores the index. Similarly, the value can also be ignored.

Multidimensional arrays

The arrays we created so far are all single dimension. It is possible to create multidimensional arrays.

In the above program in line no. 17, a two dimensional string array a has been declared using short hand syntax. The comma at the end of line no. 20 is necessary. This is because of the fact that the lexer automatically inserts semicolons according to simple rules. Please read https://golang.org/doc/effective_go.html#semicolons if you are interested to know more about why a semicolon is needed.

Another 2d array b is declared in line no. 23 and strings are added to it one by one for each index. This is another way of initializing a 2d array.

The printarray function in line no. 7 uses two for range loops to print the contents of 2d arrays. The above program will print

That’s it for arrays. Although arrays seem to be flexible enough, they come with the restriction that they are of fixed length. It is not possible to increase the length of an array. This is where slices come into the picture. In fact in Go, slices are more common than conventional arrays.

A slice is a convenient, flexible and powerful wrapper on top of an array. Slices do not own any data on their own. They are just references to existing arrays.

Creating a slice

A slice with elements of type T is represented by []T

The syntax a[start:end] creates a slice from array a starting from index start to index end - 1 . So in line no. 9 of the above program a[1:4] creates a slice representation of the array a starting from indexes 1 through 3. Hence the slice b has values [77 78 79] .

Let’s look at another way to create a slice.

In the above program in line no. 9, c := []int{6, 7, 8} creates an array with 3 integers and returns a slice reference which is stored in c.

modifying a slice

A slice does not own any data of its own. It is just a representation of the underlying array. Any modifications done to the slice will be reflected in the underlying array.

In line number 9 of the above program, we create dslice from indexes 2, 3, 4 of the array. The for loop increments the value in these indexes by one. When we print the array after the for loop, we can see that the changes to the slice are reflected in the array. The output of the program is

When a number of slices share the same underlying array, the changes that each one makes will be reflected in the array.

In line no. 9, in numa[:] the start and end values are missing. The default values for start and end are 0 and len(numa) respectively. Both slices nums1 and nums2 share the same array. The output of the program is

From the output, it’s clear that when slices share the same array. The modifications made to the slice are reflected in the array.

length and capacity of a slice

The length of the slice is the number of elements in the slice. The capacity of the slice is the number of elements in the underlying array starting from the index from which the slice is created.

Let’s write some code to understand this better.

In the above program, fruitslice is created from indexes 1 and 2 of the fruitarray . Hence the length of fruitslice is 2.

The length of the fruitarray is 7. fruiteslice is created from index 1 of fruitarray . Hence the capacity of fruitslice is the no of elements in fruitarray starting from index 1 i.e from orange and that value is 6 . Hence the capacity of fruitslice is 6. The program prints length of slice 2 capacity 6 .

A slice can be re-sliced upto its capacity. Anything beyond that will cause the program to throw a run time error.

In line no. 11 of the above program, fruitslice is re-sliced to its capacity. The above program outputs,

creating a slice using make

func make([]T, len, cap) []T can be used to create a slice by passing the type, length and capacity. The capacity parameter is optional and defaults to the length. The make function creates an array and returns a slice reference to it.

The values are zeroed by default when a slice is created using make. The above program will output [0 0 0 0 0] .

Appending to a slice

As we already know arrays are restricted to fixed length and their length cannot be increased. Slices are dynamic and new elements can be appended to the slice using append function. The definition of append function is func append(s []T, x ...T) []T .

x …T in the function definition means that the function accepts variable number of arguments for the parameter x. These type of functions are called variadic functions .

One question might be bothering you though. If slices are backed by arrays and arrays themselves are of fixed length then how come a slice is of dynamic length. Well what happens under the hood is, when new elements are appended to the slice, a new array is created. The elements of the existing array are copied to this new array and a new slice reference for this new array is returned. The capacity of the new slice is now twice that of the old slice. Pretty cool right :). The following program will make things clear.

In the above program, the capacity of cars is 3 initially. We append a new element to cars in line no. 10 and assign the slice returned by append(cars, "Toyota") to cars again. Now the capacity of cars is doubled and becomes 6. The output of the above program is

The zero value of a slice type is nil . A nil slice has length and capacity 0. It is possible to append values to a nil slice using the append function.

In the above program names is nil and we have appended 3 strings to names . The output of the program is

It is also possible to append one slice to another using the ... operator. You can learn more about this operator in the variadic functions tutorial.

In line no. 10 of the above program food is created by appending fruits to veggies . Output of the program is food: [potatoes tomatoes brinjal oranges apples]

Passing a slice to a function

Slices can be thought of as being represented internally by a structure type. This is how it looks,

A slice contains the length, capacity and a pointer to the zeroth element of the array. When a slice is passed to a function, even though it’s passed by value, the pointer variable will refer to the same underlying array. Hence when a slice is passed to a function as parameter, changes made inside the function are visible outside the function too. Lets write a program to check this out.

The function call in line number 17 of the above program decrements each element of the slice by 2. When the slice is printed after the function call, these changes are visible. If you can recall, this is different from an array where the changes made to an array inside a function are not visible outside the function. Output of the above program is,

Multidimensional slices

Similar to arrays, slices can have multiple dimensions.

The output of the program is,

Memory Optimisation

Slices hold a reference to the underlying array. As long as the slice is in memory, the array cannot be garbage collected. This might be of concern when it comes to memory management. Lets assume that we have a very large array and we are interested in processing only a small part of it. Henceforth we create a slice from that array and start processing the slice. The important thing to be noted here is that the array will still be in memory since the slice references it.

One way to solve this problem is to use the copy function func copy(dst, src []T) int to make a copy of that slice. This way we can use the new slice and the original array can be garbage collected.

In line no. 9 of the above program, neededCountries := countries[:len(countries)-2] creates a slice of countries barring the last 2 elements. Line no. 11 of the above program copies neededCountries to countriesCpy and also returns it from the function in the next line. Now countries array can be garbage collected since neededCountries is no longer referenced.

I have compiled all the concepts we discussed so far into a single program. You can download it from github .

Thats it for arrays and slices. Thanks for reading.

I hope you liked this tutorial. Please leave your feedback and comments. Please consider sharing this tutorial on twitter and LinkedIn . Have a good day.

If you would like to advertise on this website, hire me, or if you have any other software development needs please email me at naveen[at]golangbot[dot]com .

Next tutorial - Variadic Functions

Previous tutorial - Switch Statement

The Dynamic Duo: Golang Arrays and Structs [Tutorial]

Getting started with using golang arrays and structs.

Welcome to this comprehensive guide focusing on two fundamental building blocks in Golang programming: Golang Arrays and Structs. As you dive into the world of Golang development, understanding these core concepts becomes crucial for effective and efficient coding. In particular, the concept of a "Golang array of structs" is a powerful data structure that marries these two elements, offering an array-based collection of structured data types. This guide aims to explore both Golang Arrays and Structs in detail, helping you master everything from basic declarations to advanced implementations.

Whether you are a beginner eager to grasp the fundamentals or an experienced professional looking to refine your knowledge, this guide will serve as a valuable resource. By diving deep into the intricacies and use-cases for both arrays and structs in Golang , you will be better equipped to build robust, performant, and maintainable code.

So let's begin our journey into the versatile and highly practical world of Golang Arrays and Structs.

How to declare and use an Array in GO

In this example, an array of integers is declared with a fixed length of 3. Then values are assigned to the elements of the array and finally the array is printed.

How to declare and use struct in GO?

In this example, a struct of type Person is declared with two fields: name and age . Then values are assigned to the fields of the struct and finally the struct is printed .

Basic Declaration and Initialization

Working with a Golang array of structs is a common practice that combines the organizational capability of arrays with the expressiveness of structs. Below we'll dive into two types of initializations: Static Initialization and Dynamic Initialization.

Static Initialization

Static initialization involves declaring an array of structs and initializing its elements at the same time. The size and structure are known beforehand. Here's how you can perform static initialization for a Golang array of structs:

In this example, we have an array named students with a fixed size of 3. Each element is of type Student , a struct with fields Name and Grade .

Dynamic Initialization

Dynamic initialization involves creating an array of structs and filling it with elements at runtime. This method is more flexible and can be useful when the array's size or content is not known in advance. To demonstrate, let's use a Golang array of structs:

Here, we first declare an array named students with a size of 3, and each element is of type Student . We then fill in the values for Name and Grade dynamically using a for loop and the Scanln method.

Nested Array of Structs in Golang

Sometimes, the complexity of your data demands a multi-level organizational structure. Nested arrays of structs in Golang can help model such intricate scenarios. In this section, we will explore how to create, initialize, and access nested structures in a Golang array of structs.

How to Create Nested Structures

Creating nested structures involves defining a struct that contains an array of another struct as one of its fields. Below is an example that demonstrates this using a Golang array of structs:

In this example, we define two structs: Subject and Student . The Student struct contains an array of Subject structs, thereby creating a nested array of structs.

Initialization and Access

Let's take the same example a step further by initializing and accessing the elements in our nested Golang array of structs:

In this example, the students array is initialized with two Student structs. Each Student struct contains an array of Subject structs. We then use nested for loops to iterate over each student and their respective subjects.

Accessing Individual Struct Elements in Golang

Once you've declared and initialized your Golang array of structs, the next step is to access the individual elements within the array. The Golang syntax makes this a straightforward task, using index and dot notation. Let's delve into how this can be done.

Using Index and Dot Notation

To access individual elements within an array of structs in Golang, you can use index notation to specify the array element, and then use dot notation to access the fields of the struct. The general syntax looks like this:

Here's a simple example illustrating how to access individual struct elements in a Golang array of structs:

In this example, we initialize a Golang array of structs named students . We then access individual elements using index and dot notation. For instance, students[0].Name accesses the Name field of the first struct element in the array.

Iterating Through an Array of Structs in Golang

Iterating through elements is often necessary when dealing with arrays, and the case is no different for a Golang array of structs. Golang offers various looping constructs, but we will focus on two common ways to iterate through an array of structs: using a for loop and the range keyword.

1. Using for Loop

The basic for loop allows you to specify the starting index, the end condition, and the increment. It provides the most control over your loop iterations. Here's an example:

In this example, we use a for loop to iterate through each element of the Golang array of structs, accessing the Name and Grade fields for each student.

2. Using range Keyword

The range keyword simplifies array iterations, automatically managing the index and value extraction for you. Below is an example of how to iterate through a Golang array of structs using range :

In this example, we use range to iterate through the Golang array of structs. The range keyword returns two values: the index i and a copy student of the struct at that index. We can then access the struct fields directly using dot notation.

Updating Struct Fields in a Golang Array of Structs

Once you've created and initialized your array, you might find the need to update specific fields within the structs. You can do this in two primary ways: direct assignment and through functions or methods . Both approaches have their benefits and can be applied based on the use-case.

1. Direct Assignment

The most straightforward way to update a field within a struct inside an array is by direct assignment. You can directly target a specific struct's field in the array and assign a new value to it. Here's an example:

In this example, we update Alice's grade to 95 and Bob's name to Robert using direct assignment in the Golang array of structs.

2. Through Functions/Methods

Another, more structured, way to update fields is by passing the array to a function or method that performs the update. This encapsulates the update logic, which is especially useful if the update logic is non-trivial. Here's how you can do it:

In this example, we define two functions, updateGrade and updateName , which take a pointer to a Student struct as an argument. We then update the struct fields through these functions, providing a more organized approach to modifying data within our Golang array of structs.

Adding and Removing Structs in a Golang Array of Structs

Arrays in Golang are of fixed size, meaning that once you declare an array, you can't add or remove elements from it. This limitation also extends to arrays of structs. However, there are various workarounds to emulate dynamic behavior in arrays.

1. Limitations and Workarounds

Because Golang arrays are of fixed size, you cannot directly add or remove elements. One workaround to achieve similar functionality is to create a new array and copy the elements over. However, for more dynamic behavior, it's usually better to use slices, which are built on top of arrays but provide dynamic resizing capabilities.

2. Slicing for Dynamic Behavior

Slices are more flexible than arrays and are often preferred for collections of structs when you require operations like adding or removing elements. Here's how you can use slices:

In this example, we declare a Golang slice of structs and then add and remove elements using the append() function and slicing, respectively.

Declare an array variable inside a struct

In Go (Golang), you can declare an array variable inside a struct just like you would declare any other field. The syntax remains the same, where you specify the type of the array and its size.

Here's an example:

In the above code:

• Students is an array of 3 strings.
• Grades is an array of 3 integers.
• TestScores is a multi-dimensional array where there are 3 arrays, each containing 4 floating-point numbers.

The struct Classroom is then initialized with example values for these fields. You can access the individual elements of the array fields just like you would with any regular array.

Default Values for Array Fields in Golang Structs

When you declare an array inside a struct in Golang, you may often want to set default values for that array. Here's how you can go about doing that.

How to Set Default Values for Array Fields in a Struct

You can initialize default values for the array fields directly when declaring the struct instance. Here's a simple example with a struct that has an integer array and a string array.

This will output:

Nested Arrays Inside Structs in Golang

Nested arrays, often called multi-dimensional arrays, can be an essential data structure for specific use-cases. In Golang, you can declare these nested arrays within structs as well. This feature is useful for organizing and encapsulating complex data structures.

Declaring Arrays within Arrays (Multidimensional Arrays) Inside Structs

You can declare a nested array inside a struct by specifying the dimensions of the array. For example, you can define a 3x3 array of integers like this:

Here's an example that initializes a Matrix struct with a 3x3 integer array:

Pointers and Arrays Inside Structs in Golang

In Golang, you can also use pointers in conjunction with arrays within structs for more dynamic and flexible data structures. Pointers allow you to reference the memory location of a value, providing a way to share and manipulate data. This can be particularly useful when working with arrays inside structs.

Declaring Arrays of Pointers Inside a Struct

You can have an array consisting of pointers as a field in your struct. Here's a simple example:

In this example, the Classroom struct has an array of pointers to Student structs. This allows you to store a reference to the students rather than their copies, enabling shared access and modification.

Declaring Pointer to an Array Inside a Struct

You can also declare a pointer to an entire array within a struct. This can be useful for situations where the array might be large, and you want to avoid copying data.

Here's how you can declare and use a pointer to an array inside a struct:

In this example, the ArrayWrapper struct has a pointer to an array of integers. This pointer allows you to modify the original array indirectly.

In this comprehensive guide, we explored various aspects of using arrays and structs in Golang. We started with basic declarations and initializations, discussing how to statically and dynamically initialize an array of structs. We delved into more complex topics like nested arrays inside structs and the use of pointers with arrays within structs. Through practical examples, the guide clarified how to access, update, and manage these data structures efficiently.

Key Takeaways:

• Static and Dynamic Initialization : Golang offers flexibility in declaring and initializing arrays and structs.
• Nested Arrays : Multi-dimensional arrays within structs can model complex systems like matrices, image manipulation, and game states.
• Access Patterns : You can use index and dot notation to access individual elements of arrays and fields of structs.
• Pointers for Flexibility : Using pointers with arrays in structs can yield memory-efficient and dynamically mutable structures.
• Practical Implications : Understanding the various ways to implement arrays within structs helps you choose the right approach for your specific needs.

Additional Resources

• Official Golang Documentation on Arrays: GoLang Docs
• Official Golang Documentation on Structs: GoLang Docs
• Stack Overflow Discussions on Golang Arrays and Structs: Stack Overflow

Deepak Prasad

He is the founder of GoLinuxCloud and brings over a decade of expertise in Linux, Python, Go, Laravel, DevOps, Kubernetes, Git, Shell scripting, OpenShift, AWS, Networking, and Security. With extensive experience, he excels in various domains, from development to DevOps, Networking, and Security, ensuring robust and efficient solutions for diverse projects. You can reach out to him on his LinkedIn profile or join on Facebook page.

Can't find what you're searching for? Let us assist you.

Enter your query below, and we'll provide instant results tailored to your needs.

If my articles on GoLinuxCloud has helped you, kindly consider buying me a coffee as a token of appreciation.

For any other feedbacks or questions you can send mail to [email protected]

Thank You for your support!!

2 thoughts on “The Dynamic Duo: Golang Arrays and Structs [Tutorial]”

Sorry but it’s completely useless compared to the subjct you metioned. Where is usage of an array variable “in” struct?

Initially the idea was just to cover golang array of structs but I understand your concern so I have added some more chapters and scenarios on declaring array variable inside a struct. Let me know if you have any further concerns.

Leave a Comment Cancel reply

Save my name and email in this browser for the next time I comment.

Notify me via e-mail if anyone answers my comment.

A Complete Guide to Arrays in Golang

Kevin Kelche

10 min read

What is an Array in Go? astro-island,astro-slot{display:contents} (self.Astro=self.Astro||{}).load=a=>{(async()=>await(await a())())()},window.dispatchEvent(new Event("astro:load"));var l;{const c={0:t=>t,1:t=>JSON.parse(t,o),2:t=>new RegExp(t),3:t=>new Date(t),4:t=>new Map(JSON.parse(t,o)),5:t=>new Set(JSON.parse(t,o)),6:t=>BigInt(t),7:t=>new URL(t),8:t=>new Uint8Array(JSON.parse(t)),9:t=>new Uint16Array(JSON.parse(t)),10:t=>new Uint32Array(JSON.parse(t))},o=(t,s)=>{if(t===""||!Array.isArray(s))return s;const[e,n]=s;return e in c?c[e](n):void 0};customElements.get("astro-island")||customElements.define("astro-island",(l=class extends HTMLElement{constructor(){super(...arguments);this.hydrate=()=>{if(!this.hydrator||this.parentElement&&this.parentElement.closest("astro-island[ssr]"))return;const s=this.querySelectorAll("astro-slot"),e={},n=this.querySelectorAll("template[data-astro-template]");for(const r of n){const i=r.closest(this.tagName);!i||!i.isSameNode(this)||(e[r.getAttribute("data-astro-template")||"default"]=r.innerHTML,r.remove())}for(const r of s){const i=r.closest(this.tagName);!i||!i.isSameNode(this)||(e[r.getAttribute("name")||"default"]=r.innerHTML)}const a=this.hasAttribute("props")?JSON.parse(this.getAttribute("props"),o):{};this.hydrator(this)(this.Component,a,e,{client:this.getAttribute("client")}),this.removeAttribute("ssr"),window.removeEventListener("astro:hydrate",this.hydrate),window.dispatchEvent(new CustomEvent("astro:hydrate"))}}connectedCallback(){!this.hasAttribute("await-children")||this.firstChild?this.childrenConnectedCallback():new MutationObserver((s,e)=>{e.disconnect(),this.childrenConnectedCallback()}).observe(this,{childList:!0})}async childrenConnectedCallback(){window.addEventListener("astro:hydrate",this.hydrate);let s=this.getAttribute("before-hydration-url");s&&await import(s),this.start()}start(){const s=JSON.parse(this.getAttribute("opts")),e=this.getAttribute("client");if(Astro[e]===void 0){window.addEventListener(`astro:${e}`,()=>this.start(),{once:!0});return}Astro[e](async()=>{const n=this.getAttribute("renderer-url"),[a,{default:r}]=await Promise.all([import(this.getAttribute("component-url")),n?import(n):()=>()=>{}]),i=this.getAttribute("component-export")||"default";if(!i.includes("."))this.Component=a[i];else{this.Component=a;for(const d of i.split("."))this.Component=this.Component[d]}return this.hydrator=r,this.hydrate},s,this)}attributeChangedCallback(){this.hydrator&&this.hydrate()}},l.observedAttributes=["props"],l))} Copy section link to clipboard

An array is a fixed-length sequence of elements of a single type. Arrays are mutable, meaning that the elements of an array can be changed after it is created. Arrays are a fundamental data structure in Go.

Arrays and slices are both used to store multiple values in a single variable. The difference between the two is that arrays have a fixed length, while slices have a dynamic length. Slices are built on top of arrays.

Creating an Array in Go Copy section link to clipboard

Arrays are used to store multiple values in a single variable, instead of declaring separate variables for each value. To declare an array, define the type of elements it will hold, and the number of elements it will hold.

Here, we have declared an array named arr that will hold 4 integers. The type of the elements is int and the array length is 4. The elements of an array are indexed starting from zero.

Here we have assigned values to the elements of the array. We can also declare and initialize an array in a single line; this is known as an array literal. As shown below.

Accessing Array Elements in Golang Copy section link to clipboard

Array elements can be accessed using the index of the element. The index of the first element is 0, and the index of the last element is the length of the array minus 1.

Iterating Over an Array in Golang Copy section link to clipboard

Array elements can be accessed using a for loop. The index of the first element is 0, and the index of the last element is the length of the array minus 1.

The output of the above code is:

We could also use the range keyword to iterate over the elements of an array.

The range keyword returns both the index and the value of the element. We can use the blank identifier _ to ignore the index.

Array Length in Golang Copy section link to clipboard

Arrays have the len function that returns the length of the array.

Since arrays are fixed-length, the length of an array cannot be changed after it is created.

Array Slicing in Golang Copy section link to clipboard

Array slicing is a technique to access a subset of an array. The syntax for array slicing is array[start:end] . The start index is inclusive, and the end index is exclusive. The start index defaults to 0, and the end index defaults to the length of the array.

Array Comparison in Golang Copy section link to clipboard

Arrays can be compared using the == operator. The == operator returns true if the two arrays have the same length and the same elements in the same order.

The last print statement returns false because the elements of arr1 and arr3 do not contain the same values.

Array Sorting in Golang Copy section link to clipboard

Arrays can be sorted using the sort package. The sort package provides the sort.Ints function that sorts an array of integers in ascending order.

Another tedious way of sorting an array is to use for loops. The following code sorts an array of integers in ascending order.

Array Copy in Golang Copy section link to clipboard

Arrays can be copied using the copy function. The copy function takes two arguments: the destination array and the source array. The copy function returns the number of elements copied.

Array Delete in Golang Copy section link to clipboard

Elements of an array can be deleted by setting the value of the element to the zero value of the type of the element. The zero value of an integer is 0.

Array Contains in Golang Copy section link to clipboard

To check if array contains a value, we can use the sort.Search function from the sort package. The sort.Search function takes three arguments: the length of the array, a function that returns true if the element at the given index is greater than or equal to the value, and the value to search for.

Array Reverse in Golang Copy section link to clipboard

Arrays can be reversed in two ways. The first way is to replace the first element with the last element, the second element with the second last element, and so on. The second way is to use the sort.Reverse function from the sort package.

Multidimensional Arrays in Golang Copy section link to clipboard

Arrays can have more than one dimension. A multidimensional array is an array of arrays. The syntax for declaring a multidimensional array is var arr [rows][columns]type . The rows and columns are the number of rows and columns in the multidimensional array, and type is the type of the elements in the multidimensional array.

Most of the operations that can be performed on a 1D array can also be performed on a multidimensional array.

2D Array in Golang Copy section link to clipboard

A 2D array is an array of arrays. The syntax for declaring a 2D array is var arr [rows][columns]type . The rows and columns are the number of rows and columns in the 2D array, and type is the type of the elements in the 2D array.

The above code declares a 2D array with 2 rows and 3 columns. The elements of the 2D array are integers.

Accessing 2D Array Elements in Golang Copy section link to clipboard

2D array elements can be accessed using the row and column index of the element. The row index of the first element is 0, and the column index of the first element is 0. The row index of the last element is the number of rows minus 1, and the column index of the last element is the number of columns minus 1.

2D Array Length in Golang Copy section link to clipboard

The len function returns the number of rows in a 2D array. The len function does not return the number of columns in a 2D array. However, we can loop through the rows of a 2D array and use the len function to get the number of columns in each row.

Array of Slices in Golang Copy section link to clipboard

An array of slices is an array where each element is a slice. The syntax for declaring an array of slices is var arr [size]type , where size is the number of elements in the array, and type is the type of the elements in the array.

The above code declares an array of slices with 2 elements. The elements of the array are slices of integers.

Array of Maps in Golang Copy section link to clipboard

An array of maps is one in which each element is a map. The syntax for declaring an array of maps is var arr [size]type .

The above code declares an array of maps with 2 elements. The elements of the array are maps with string keys and integer values.

Array of Functions in Golang Copy section link to clipboard

An array of functions is one where each element is a function. The syntax for declaring an array of functions is var arr [size]type .

The above code declares an array of functions with 2 elements. The elements of the array are functions that take an integer as an argument and return an integer.

Array of Interfaces in Golang Copy section link to clipboard

An array of interfaces is one where each element is an interface. The syntax for declaring an array of interfaces is var arr [size]type .

The above code declares an array of interfaces with 2 elements. The elements of the array are an integer and a string.

Array of Pointers in Golang Copy section link to clipboard

An array of pointers is one where each element is a pointer. The syntax for declaring an array of pointers is var arr [size]type .

The above code declares an array of pointers with 2 elements. The elements of the array are pointers to integers.

Array of Channels in Golang Copy section link to clipboard

An array of channels is one where each element is a channel. The syntax for declaring an array of channels is var arr [size]type .

The above code declares an array of channels with 2 elements. The elements of the array are channels of integers.

Array of Structs in Golang Copy section link to clipboard

An array of structs is one where each element is a struct. The syntax for declaring an array of structs is var arr [size]type .

The above code declares an array of structs with 2 elements. The elements of the array are Person structs.

Tl;dr Copy section link to clipboard

Arrays are a data structure that stores a fixed number of elements of the same type. Arrays are zero-indexed, meaning an array's first element is at index 0. Arrays can be declared using the var keyword, and the elements of an array can be accessed using the index of the element.

Thank you for reading and happy coding! Have any questions? Feel free to reach out to me on Twitter -

Subscribe to my newsletter

Get the latest posts delivered right to your inbox.

How To Work With Golang Array

Arrays in Go offer a unique blend of simplicity and efficiency. In this article, we explore the intricacies of golang arrays, from their definition to common operations. Join us as we delve into practical examples tailored for developers keen on refining their Go skills.

Golang, or Go, offers a unique approach to array data structures. Unlike other languages, Go's arrays have a fixed size, ensuring consistent performance. Familiarity with this concept can enhance a developer's toolkit when working with Go.

💡 KEY INSIGHTS

• In Golang, arrays have a fixed size which is part of their type, offering consistent performance and predictability.
• Initializing arrays can be done with specific values or using the zero value of the array's element type.
• Accessing and modifying array elements is achieved through index-based operations , with bounds checking for safety.
• For iterating over arrays , Go provides traditional for loops and range-based loops for efficient element traversal.

Understanding Golang Arrays

Defining and initializing arrays, accessing array elements, iterating over arrays, modifying array elements, array bounds and safety, multidimensional arrays, common array operations, frequently asked questions.

In the world of programming, an array is a collection of elements, all of the same type, accessed using indices. In Go, arrays are unique in that their length is part of their type. This means the size of an array is fixed and can't change during runtime.

Syntax And Initialization

Length and capacity.

The general syntax to declare an array in Go is:

For example, to declare an integer array of size 5:

To initialize an array with values:

It's important to note that, unlike slices, arrays have a fixed size. The len() function will always return the size you declared, irrespective of the number of elements present.

Get the length of an array:

I hope this provides a clear and concise understanding of arrays in Go. Practice working with them, and you'll grasp their advantages and limitations in no time.

Arrays are fundamental in Go, offering a means to store a fixed-size sequence of elements of a single type. Defining and initializing these arrays are primary steps any Go developer needs to grasp.

Array Declaration

Array initialization, short declaration, zero values, using [...] for size.

Declaring an array is straightforward. You specify the type of element the array will hold, and the number of elements it will contain.

While arrays can be declared without initializing, it's often practical to provide values at the start.

Go provides a concise way to declare and initialize arrays using the short declaration syntax.

If an array is declared but not initialized, its elements take the zero value of the array's type.

Go allows the use of ... instead of specifying the size, letting the compiler determine the size based on the number of initialized values.

Defining and initializing arrays is a fundamental aspect of Go. By understanding the different methods and nuances, you set a solid foundation for efficient data handling in your applications.

Arrays in Go are collections of elements. To manipulate or use these elements, it's essential to understand how to access them. Access is primarily achieved using an index , which denotes the position of the element in the array.

Using Indices

Bounds checking, accessing using loops, modifying elements.

Every element in an array has an index, starting from 0 and incrementing by 1 for each subsequent element.

It's crucial to remember that Go performs bounds checking. Trying to access an index outside the valid range will result in a runtime panic .

To access multiple elements, loops come in handy. They allow systematic traversal of an array.

Accessing is not just for retrieval. You can also modify elements by assigning a new value to a specific index.

Accessing and manipulating elements form the core of array operations in Go. By mastering index-based access, you pave the way for more advanced operations and algorithms in your Go applications.

Iterating, or looping, over arrays is a common operation when working with collections of data. It allows for sequential access to each element in the array, making it easy to perform operations like data transformation, computation, or display.

Traditional For Loop

Using range, ignoring the index or value, nested arrays.

The traditional for loop offers a basic way to iterate over array elements using indices.

Go provides the range keyword, a more idiomatic way to iterate over collections, including arrays. The range returns both the index and the value at that index for every iteration.

At times, you might only be interested in the value and not the index (or vice versa). In such scenarios, the _ (blank identifier) can be used to ignore unwanted values.

When working with multidimensional arrays, nested loops come into play.

Looping over arrays is fundamental in Go, and knowing the nuances of the different techniques ensures efficient and effective data manipulation. Whether it's the traditional for loop or the idiomatic range , Go offers powerful tools to work with array data.

In Go, arrays are not just static data structures. They are dynamic entities, and their individual elements can be modified as needed. This flexibility allows developers to adjust data on-the-fly, catering to evolving application requirements.

Direct Assignment

Using loops for modification, restrictions and pitfalls, partial updates with slices.

The most straightforward way to modify an array element is through direct assignment using an index.

For scenarios where multiple elements need adjustment, loops can be employed.

While modifying, always be mindful of the array's bounds . Assigning a value to an index outside the existing range results in a runtime panic.

Slices, derived from arrays, can also facilitate modifications, especially when targeting a subsection of the array.

Modifying array elements is a routine task in many applications. Whether you're updating single entries or making bulk adjustments, Go provides intuitive and efficient mechanisms to achieve this. Ensure you're mindful of array bounds and leverage the power of both arrays and slices for versatile data management.

In Go, the integrity and safety of data structures are paramount. When dealing with arrays, ensuring that access remains within the boundaries of the array's size is crucial. An attempt to access or modify elements outside these bounds leads to errors, promoting code safety.

Runtime Panic On Out-Of-Bounds Access

Using the len function for safety, defensive programming.

Go performs automatic bounds checking for arrays. If you attempt to access or modify an element using an index outside the valid range, the program will trigger a runtime panic .

To avoid out-of-bounds issues, always ensure that indices are within the valid range. One way to achieve this is by using the len function, which returns the size of the array.

Adopting a defensive programming mindset is essential. Always validate indices, especially if they come from user input or other external sources.

Bound checking is one of Go's mechanisms to enforce safety. By understanding and respecting array boundaries, developers can write secure, error-free code that stands the test of time.

Arrays in Go are versatile. Beyond the single-dimensional arrays we commonly encounter, Go supports multidimensional arrays . These are arrays within arrays, commonly used to represent structures like matrices or data tables.

Defining A 2D Array

Initialization of 2d arrays, accessing elements in 2d arrays, iterating over multidimensional arrays, higher dimensions.

A two-dimensional (2D) array is akin to a matrix, having both rows and columns.

Just as with single-dimensional arrays, multidimensional arrays can be initialized with values at declaration.

To access a specific element within a multidimensional array, you specify the indices for each dimension.

Looping over multidimensional arrays typically requires nested loops.

Go isn't limited to just 2D arrays. You can define arrays with three, four, or more dimensions if needed. However, as dimensions increase, comprehension and maintenance can become more challenging.

Multidimensional arrays are powerful tools, particularly useful in fields like scientific computing and graphics. By mastering their definition, initialization, and traversal, you'll be equipped to handle complex data structures and algorithms in Go.

In Go, arrays are fundamental data structures, and there are several common operations you might perform on them. Whether it's determining the size, copying, or comparing, understanding these operations can streamline your coding tasks.

Determining The Length

Comparing arrays, copying arrays, finding elements, filling an array.

The len function provides the length or number of elements in an array.

In Go, you can directly compare arrays of the same type and size using relational operators.

Copying in Go is achieved through assignment. But remember, this creates a shallow copy.

To find an element in an array, you'd typically loop through its elements.

To populate an array with a default value, use a loop.

Arrays are a cornerstone in Go programming, and mastering these common operations will greatly enhance your productivity. As you work with arrays, always be mindful of their fixed size and remember the distinction between value and reference types to ensure accurate and safe manipulations.

How Do You Access an Element in a Golang Array?

Array elements can be accessed using their index. For example, arrayName[index] .

Can You Change the Size of a Golang Array After Declaration?

No, once a Golang array is declared, its size is fixed. For dynamic sizes, consider using slices.

What Happens If I Try to Access an Index Outside of the Array's Range?

If you attempt to access an index outside the valid range of the array, it will result in a runtime panic.

What's the Difference Between a Golang Array and Slice?

While arrays have a fixed size in Go, slices are dynamic. Slices, unlike arrays, can grow and shrink during runtime. They are built on top of arrays and provide greater flexibility.

How Do You Iterate Over a Golang Array?

You can iterate over a Golang array using a for loop or the range keyword, which offers a more idiomatic way to loop over elements.

Let’s test your knowledge!

What is the default value of an integer array in Go?

Continue learning with these golang guides.

• How To Work With Golang Make Effectively
• How To Work With Golang Substring Operations
• Getting Started With Golang Playground
• How To Excel With Golang Tutorial
• How To Handle Golang Panic Effectively

Subscribe to our newsletter

Subscribe to be notified of new content on marketsplash..

Implementation principles of Go language arrays

Table of contents.

Arrays and slices are common data structures in the Go language, and many developers new to Go tend to confuse these two concepts. In addition to arrays, Go introduces another concept - slicing. Slicing has some similarities to arrays, but their differences lead to significant differences in usage. In this section we will introduce the underlying implementation of arrays from the Go compile-time runtime, which will include several common operations for initializing, accessing, and assigning values to arrays.

An array is a data structure consisting of a collection of elements of the same type. The computer allocates a contiguous piece of memory for the array to hold its elements, and we can use the indexes of the elements in the array to quickly access specific elements. Most common arrays are one-dimensional linear arrays, while multidimensional arrays have more common applications in numerical and graphical computing.

As a basic data type, arrays are usually described in two dimensions, namely the type of elements stored in the array and the maximum number of elements that the array can store. In Go language we tend to use the following representation of array types as shown below.

Go arrays cannot be changed in size after initialization, and arrays that store elements of the same type but different sizes are considered completely different in Go, and are the same type only if both conditions are the same.

The array type during compilation is generated by the above cmd/compile/internal/types.NewArray function, which contains two fields, the element type Elem and the size of the array Bound, which together form the array type, and whether the current array should be initialized on the stack is determined at compile time.

Initialization

Arrays in Go are created in two different ways, either by explicitly specifying the size of the array, or by using […] T to declare the array, and Go will derive the size of the array from the source code during compilation.

The above two declaration methods get exactly the same result during runtime. The latter declaration method is converted to the former one during compilation, which is the compiler’s derivation of the array size, and we will introduce the compiler’s derivation process below.

Upper bound derivation

The two different declarations lead to completely different treatment by the compiler. If we use the first way [10]T, then the type of the variable is extracted as soon as the compilation proceeds to the type checking stage, and the cmd/compile/internal/types.NewArray containing the array size is subsequently created using cmd/compile/internal/types. Array structure containing the array size.

When we declare an array using […] T, the compiler will derive the size of the array in the cmd/compile/internal/gc.typecheckcomplit function.

This truncated cmd/compile/internal/gc.typecheckcomplit calls cmd/compile/internal/gc.typecheckarraylit to count the number of elements in the array by traversing the elements.

So we can see that […] T{1, 2, 3} and [3]T{1, 2, 3} are exactly equivalent at runtime, […] T initialization is just a kind of syntactic sugar provided by the Go language to reduce the workload when we don’t want to count the number of elements in the array.

Statement conversion

For an array of literals, depending on the number of array elements, the compiler does two different optimizations in the cmd/compile/internal/gc.anylit function, which is responsible for initializing the literals.

• when the number of elements is less than or equal to 4, the elements of the array will be placed directly on the stack.
• when the number of elements is greater than 4, the elements of the array are placed in the static area and removed at runtime.

When the array has less than or equal to four elements, cmd/compile/internal/gc.fixedlit takes care of converting [3]{1, 2, 3} to a more primitive statement before the function is compiled.

When the number of elements in the array is less than or equal to four and the kind received by the cmd/compile/internal/gc.fixedlit function is initKindLocalCode, the above code splits the original initialization statement [3]int{1, 2, 3} into an expression declaring a variable and several assignment expressions. These expressions will complete the initialization of the array:

However, if the current array has more than four elements, cmd/compile/internal/gc.anylit will first get a unique staticname and then call the cmd/compile/internal/gc.fixedlit function to initialize the elements of the array in static storage and assign temporary variables to the array :

Assuming that the code needs to initialize [5]int{1, 2, 3, 4, 5}, then we can interpret the above procedure as the following pseudo-code.

To summarize, without considering escape analysis, if the number of elements in the array is less than or equal to 4, then all variables will be initialized directly on the stack, and if the array has more than 4 elements, the variables will be initialized in static storage and then copied to the stack.

Access and assignment

Whether on the stack or in static storage, arrays are a sequence of memory spaces in memory. We represent arrays by a pointer to the beginning of the array, the number of elements, and the size of the space occupied by the element type. If we do not know the number of elements in the array, an out-of-bounds access may occur; and if we do not know the size of the element types in the array, there is no way to know how many bytes of data should be taken out at a time, and whichever information is missing, we have no way of knowing what data is actually stored in this contiguous memory space: the

Out-of-bounds array access is a very serious error, and can be determined by static type checking during compilation in Go. cmd/compile/internal/gc.typecheck1 verifies that the index of the accessed array.

• the error “non-integer array index %v” is reported when accessing an array whose index is a non-integer.
• the error “invalid array index %v (index must be non-negative)” is reported when the index of the accessed array is negative.
• the error “invalid array index %v (out of bounds for %d-element array)” is reported when the index of the accessed array is out of bounds.

Some simple out-of-bounds errors for arrays and strings are found during compilation, e.g. accessing an array directly with an integer or constant; however, when accessing an array or string with a variable, the compiler cannot detect the error in advance, and we need the Go runtime to prevent illegal accesses.

Out-of-bounds operations on arrays, slices and strings found by the Go runtime are triggered by runtime.panicIndex and runtime.goPanicIndex, which trigger a runtime error and cause a crash and exit.

When the array access operation OINDEX successfully passes the compiler’s checks, it is converted into several SSA directives. Suppose we have Go code as shown below, compiling it in the following way will result in the ssa.html file.

The SSA code generated in the start phase is the first version of the intermediate code before the optimization, which is shown below for elem := arr[i].

In this intermediate code, we find that Go generates the instruction IsInBounds to determine the upper limit of the array and the PanicBounds instruction to crash the program if the condition is not met.

When the array subscript is not out of bounds, the compiler will first obtain the memory address of the array and the subscript to be accessed, calculate the address of the target element using PtrIndex, and finally load the element in the pointer into memory using the Load operation.

Of course, only when the compiler is unable to make a judgment on whether the array subscript is out of bounds or not, it will add the PanicBounds instruction to the runtime to make a judgment.

It not only finds simple out-of-bounds errors in advance during compilation and inserts function calls to check the upper limit of the array, but also ensures that no out-of-bounds occur during runtime with the inserted functions.

The array assignment and update operation a[i] = 2 also generates the SSA generation which calculates the memory address of the current element of the array during generation and then modifies the contents of the current memory address, these assignment statements are converted into SSA code as follows.

The assignment process will first determine the address of the target array, and then get the address of the target element through PtrIndex.

Finally, the Store instruction is used to store the data into the address. From the above SSA code, we can see that the above array addressing and assignment are done at the compilation stage without any runtime involvement.

Arrays are an important data structure in Go, and understanding its implementation can help us understand the language better. Through the analysis of its implementation, we know that accessing and assigning values to arrays depends on both the compiler and the runtime, and most of its operations are converted into direct memory reads and writes during compilation. panicIndex call to prevent out-of-bounds errors from occurring.

Programming Geeks Club

• April 28, 2023

Multi-Dimensional Arrays in Golang: A Complete Guide

Go (or Golang) is a statically-typed, Compiled Programming Language designed by Google to offer efficient and reliable software development. One of the most crucial aspects of any programming language is its ability to manipulate and store data. Multi-dimensional arrays, Also known as arrays of arrays, are a widely used data structure in programming. In this guide, We will delve into the use of multi-dimensional arrays in Golang, Providing a comprehensive overview of how to create, manipulate, and iterate through them.

Understanding Arrays in Golang

In Golang, An array is a fixed-length sequence of elements with the same data type. Arrays are value types, Which means that assigning an array to another variable copies the data, not the reference. The following code snippet demonstrates how to declare and initialize a simple one-dimensional array in Golang:

• python pip TensorFlow installation
• Why Rust is a Serious Contender to Replace C++
• Selection sort algorithm

Creating Multi-Dimensional Arrays

Multi-dimensional arrays in Golang are arrays with arrays as their elements. To create a multi-dimensional array, You specify the dimensions within the square brackets while declaring the array variable. Here’s an example of a 3×3 two-dimensional array in Go:

You can also create and initialize a multi-dimensional array in one step:

Accessing Elements in Multi-Dimensional Arrays

Accessing elements in a multi-dimensional array is similar to accessing elements in a one-dimensional array. You simply need to use the array variable followed by the index of each dimension inside square brackets. Here’s an example:

Manipulating Multi-Dimensional Arrays

Modifying the elements of a multi-dimensional array is as simple as assigning a new value to the element at a specified index, Here’s an example:

Iterating Through Multi-Dimensional Arrays

To iterate through a multi-dimensional array, You can use nested loops. The outer loop iterates through the rows, While the inner loop iterates through the columns. Here’s an example:

Practical Use Cases

Multi-dimensional arrays have various practical applications in computer programming, Some common use cases include:

• Representing matrices in mathematical computations.
• Creating and manipulating images as a grid of pixels.
• Storing data in tables with rows and columns, such as spreadsheets or databases.
• Implementing game boards for tic-tac-toe, chess, or other grid-based games.

In this complete guide of multi-dimensional arrays in Golang, we covered how to create, access, manipulate, and iterate through these data structures, With a solid understanding of multi-dimensional arrays, You can efficiently handle various tasks in Golang, Especially those requiring the representation and manipulation of complex data structures.

Although multi-dimensional arrays are a powerful tool, Golang also offers more flexible data structures like slices and maps, Which can be more suitable for certain use cases. As you continue to explore Golang, be sure to familiarize yourself with these alternative data structures as well, so you can choose the most appropriate tool for your programming tasks.

Join Our Newsletter!

Join our newsletter to get our latest ebook " Ultimate JavaScript Cheat-Sheet ", and Tips, Articles..

We don’t spam! Read our privacy policy for more info.

You’ve been successfully subscribed to our newsletter, and will be sent to your mail address.

Tags: Array multi dimensional array

You may also like...

The Advantages Of Using Go

How to write a programming blog post that will go viral

Best FREE YouTube Video Downloader (2023)

Leave a reply cancel reply.

Your email address will not be published. Required fields are marked *

Save my name, email, and website in this browser for the next time I comment.

 Yes, add me to your mailing list

• Next Golang Generics: Array Sums Redefined
• Previous Master Golang String Manipulation in 5 Easy Steps: A Comprehensive Guide

How to Pickle and Unpickle Objects in Python: A Complete Guide

Ultimate Python Multithreading Guide

Google PlayStore Banned iRecorder APP For Using AhRat Malware

NPM Packages Found Hiding Dangerous TurkoRat Malware

The Recent Security Threats on Python Package Index (PyPI) and Its Implications

Stay Alert: The Rising Threat of Malicious Extensions in Microsoft’s VSCode Marketplace

How to Create Custom Array/Slice Methods in Go: A Simple Guide

Revolutionizing AI Tech: ChatGPT Code Interpreter Plugin Outshines GPT-4

AutoGPT: A Game-Changer in the World of AI Applications