assignment operator mql4

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One operator can occupy one or more lines. Two or more operators can be located in the same line. Operators that control over the execution order (if, if-else, switch, while and for), can be nested into each other.

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Operators and Expressions in MQL4

In MQL4, operators are the building blocks used to create expressions. These expressions allow you to perform operations like arithmetic, comparison, and logic on your data.

Arithmetic Operators

These operators perform basic mathematical operations:

• + Addition: int result = 5 + 3; // result is 8
• - Subtraction: int result = 5 - 3; // result is 2
• * Multiplication: double result = 4.5 * 2; // result is 9.0
• / Division: double result = 9.0 / 2; // result is 4.5
• % Modulus (remainder): int result = 11 % 3; // result is 2

double PriceDifference =(OrderStoploss() - OrderOpenPrice());

This example creates for us a "double", that will tell us the difference between where the stoploss is placed and where a sell trade was opened.

Comparison Operators

These operators compare two values and return a boolean (true or false) result. Here are some very basic examples to try to explain this better:

== (Equal to)

Heres how to use it:

!= (Not equal to)

> (Greater than)

>= (Greater than or equal to)

if(Close[1]>Close[2]) { /* Your trading logic here */ }

This conditional statement evaluates if the closing value of a candle one period prior is greater than the closing value of a candle two periods prior. If this condition is met, the subsequent logic encapsulated within the curly braces `{ }` is executed.

if(Open[2]==Close[3]) { /* Enter trade or some other action */ }

This statement checks if the open of the candle 2 periods ago is equal to the close of 3 candles ago. If the condition is satisfied, the code within the `{ }` is triggered.

At the heart of algorithmic trading lies the conditional statement. As you craft your Expert Advisor (EA), experimenting with elementary conditions will bolster your proficiency.

For enhanced readability, you may opt to enclose individual conditions within parentheses, as illustrated below:

if( ( Close[1]>Close[2] ) && ( Open[2]==Close[3] ) ){ /* Your trading logic here */ }

Here is an example from our test EA, using MyFirstCondition that was initially set to false in the global variables section... Now it would be set to true, if this condition were met, until it is reset back to false by some other condtion.

Logical Operators

These operators combine boolean expressions and return a boolean result. This just means that they are ways in code of saying AND , OR and NOT :

• && means AND: (1 > 2 && 4 > 3); // result is false because both conditions are not true... Only one is.
• || means OR: (1 > 2 || 2 > 1); // result is true because this statement is asking if 1 is greater than 2 OR if 2 is greater than 1. As long as one of these statements is true, the condition is fulfilled.
• ! means NOT: (5 + 4 != 1); // result is true because 5 + 4 is NOT equal to 1

if((1 + 2 = 3) && (2 + 3 = 6) || (1 + 1 = 3) || (7 - 7 != 3)){ //Your code to enter trade here}

This above conditions result would still be true simply because the 3rd condition is true. 7 - 7 is NOT equal to 3... Even though our first 2 condtions will never be true in this example.

Assignment Operators

These operators assign values to variables:

• = Assign: int a = 5;
• += Add and assign: a += 3; // a is now 8
• -= Subtract and assign: a -= 2; // a is now 6
• *= Multiply and assign: a *= 2; // a is now 12
• /= Divide and assign: a /= 3; // a is now 4

Although the above may be confusing, it is simply a method of changing a value as circumstances evolve.

1. We begin with the integer that we named "a" and we assined it a value of 5. int a = 5;

2. Then we used += to alter its value. The + is telling the EA to use addition and the = is telling the EA that we are to now assign the resulting number as the new value for the EA. a += 3 = 8 because 5 + 3 = 8

3. Now using the same principles we are going to subtract 2 from the new value of "a" and asign the result as the new value. 8 - 2 = 6, so a now equals 6.

4. Now, we are have told the EA to multiply our new value of "a" by 2 and to assin that as its new value. 6 * 2 = 12 .

5. Finally we are telling the EA to divide our newest value of "a" by 3. 12 / 3 = 4, therefore the final value of "a" has become 4.

This example is not a very real world example but is meant to display the capabilites of mql4 coding.

Lets now try out some of our new skills in our test EA.

Operators in MQL4 are essential tools that allow you to manipulate and evaluate data. Understanding them thoroughly can significantly enhance the effectiveness and efficiency of your algorithms.

NEXT UP: Loops and Conditional Statements.

Operators in MQL4

Compound operator, terminator operator, conditional operators, loop operators.

What is a program? A program is a sequence of operations put together to perform one or more tasks. These operations are performed through operators . In this guide, you can see what operators are in MQL4 programming language and, more importantly, how to use them.

An operator can be defined as a character, or sequence of characters, that drives MetaTrader to perform an action. A very simple example that is used with variables is the = character. When you write int i = 10; , the operator =  is an assignment operator, while ;  (a semicolon) is an empty operator to finish the action.

MQL4 has many types of operators, too many to cover them all in one guide. You will only learn about a few of them for the moment. To start getting familiar with some code, you will see examples and explanations for them with comments .

This was just an introduction to operators in MQL4. There is a wide variety of them for different purposes. The more you will code, the more operators you will face, learning to embrace them and use them in order to achieve your coding goals.

If you want to get news of the most recent updates to our guides or anything else related to Forex trading, you can subscribe to our monthly newsletter .

Are there no "and" "or" operators in mql4??

I am just learning to code mql4 and it appears as though there are no "and" "or" operators which are common to almost any programming language. In the mql4 documentation it gives the usual bitwise and logical operators but no "and" "or". Does this mean that all expressions comparing various conditions will have to be a complicated combination of nested if else and switch statements. Is there no way to write an expression such as this in mql4 without using nested if or switch statements: if(((a>b) and (e>b)) or (r>s)) {} ?

Thank you for your time

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• [ARCHIVE!] Any rookie question, so as not to clutter up the forum. Professionals, don't pass by. Can't go anywhere without you - 4.
• How the "and" & "or" operators work, when both combined in an if statement.

use this && for "and"

|| for "or"

if(((a>b) && (e>b)) || (r>s))

blah blah blah

thanks, ejoi

Use of logical operators

I am trying to write and "if" statement that requires the use of two &&.

for example if ( A>B && C>D && E>F) buy

if (A<B && C<D && E<F) sell

When compilig I get no errors. However, the system seems to hangup and does not do anything. I have tried using a single && and everything works fine. Is there a way to use two or more && in a single "if" statement

Something is definately wrong with your code. There is nothing wrong with those 2 statements.

Try validating each condition individually and see which one stalls, e.g.

if (A>B) Print("1");

if (C>D) Print("2");

if (E>F) Print("3");

If a sequence of 1,2,3 doesn't appear in your Journal, then you'd know which condition fails.

Not the Language

I have put up to 5 &&s in an If statement and there wasn't any problem. I suppose you could bracket your conditions, but this should only be necessary for || (ors). There is definitely something wrong with your code. Its probably very subtle.

OrderSend(); //Buy

if ((A < B) && (C < D) && (E < F))

OrderSend(); //Sell

I have a similar problem.

This simple code alway give "true" as result, when must give "false". Any idea about the problem?

Thanks in advace

You re using assignment operator for boolleans not comparison operator

Change that to this

and it will work OK

I try used operator && if more time

but doesn't work Is this  correct?

“Doesn't work” is meaningless — just like saying the car doesn't work. Doesn't start, won't go in gear, no electrical, missing the key, flat tires — meaningless.       How To Ask Questions The Smart Way . 20 04            When asking about code

Use the debugger or print out your variables, including _LastError and prices and find out why . Do you really expect us to debug your code for you?

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Execution Examples of the Operator 'if-else'

Let us consider some examples that demonstrate how we can use the operator 'if-else'.

One of solutions for this problem may be, for example, as follows ( onelevel.mq4 ):

It should be noted, first of all, that the program is created as an Expert Advisor. This implies that the program will operate for quite a long time in order to display the necessary message on the screen as soon as the price exceeds the preset level. The program has only one special function, start(). At the start of the function, the variables are declared and commented. Then the price level is set in numeric values and the current price is requested.

The operator 'if-else' is used in the following lines of the program:

As soon as the control in the executing program is passed to the operator 'if-else', the program will start to test its condition. Please note that the conditional test in the operator 'if-else' is the inherent property of this operator. This test cannot be omitted during execution of the operator 'if-else', it is a "raison d'etre" of this operator and will be performed, in all cases. Thereafter, according to the results of this test, the control will be passed to either the operator's body or outside it - to the operator that follows the closing brace.

In Fig. 37 below, you can see a block diagram representing a possible event sequence at execution of the operator 'if-else'.

In this and all following diagrams, a diamond represents the conditional check. Arrows show the target components, to which the control will be passed after the current statement block has been executed (the term of statement block means a certain random set of operators adjacent to each other). Let's consider the diagram in more details.

The block of "Previous Calculations" (a gray box in the diagram) in program onelevel.mq4 includes the following:

After the last operator in this block has been executed, the control is passed to the header of the operator 'if-else' where the condition of Does the price exceed the preset level? (the diamond box in the diagram, Fig. 37) is checked:

In other words, we can say that the program at this stage is groping for the answer to the following question: Is the statement enclosed in parentheses true? The statement itself sounds literally as it is written: The value of the variable Price exceeds that of the variable Level (the price exceeds the preset level). By the moment of checking this statement for being true or false, the program has already had the numeric values of variables Price and Level. The answer depends on the ratio between these values. If the price is below the preset level (the value of Price is less or equal to the value of Level), the statement is false; if the price exceeds this level, the statement is true.

Thus, where to pass the control after the conditional test depends on the current market situation (!). If the price for a symbol remains below the preset level (the answer is No , i.e., the statement is false ), the control, according to the execution rule of the operator ' if-else' , will be passed outside the operator, in this case, to the block named Subsequent Calculations , namely, to the line:

As is easy to see, no message to the trader is given.

If the price for a symbol exceeds the level preset in the program (the answer is Yes, i.e., the statement is true ), the control will be passed to the body of the operator 'if-else', namely, to the following lines:

The execution the function Alert() will result in displaying on the screen a small box containing the following message:

The function Alert() is the only operator in the body of the operator 'if-else', this is why after its execution, the operator 'if-else' is considered to be completely executed, and the control is passed to the operator that follows the operator 'if-else', i.e., to line:

The execution of the operator 'return' results in that the function start() finishes its work, and the program switches to the tick-waiting mode. At a new tick (that also bears a new price for the symbol), the function start() will be executed again. So the message coded in the program will or won't be given to the trader depending on whether the new price exceeds or does not exceed the preset level.

The operators 'if-else' can be nested. In order to demonstrate how the nested operators can be used, let's consider the next example. The problem in it is a bit more sophisticated.

It is clear that, in order to solve this problem, we have to check the current price twice:

1. compare the price to level 1, and

2. compare the price to level 2.

Solution 1 of Problem 10

Acting formally, we can compose the following solution algorithm:

The program that realizes this algorithm can be as follows ( twolevel.mq4 ) :

As is easy to see, the code in program twolevel.mq4 is the extended version of program onelevel.mq4 . If we had only one level of calculations before, we have two levels in this new program. Each level was defined numerically, and the program, to solve the stated problem, has two blocks that track the price behavior: Falls the price within the range of values limited by the preset levels or is it outside this range?

Let's give a brief description of the program execution.

After the preparatory calculations have been performed, the control is passed to the first operator 'if-else':

Whatever events take place at the execution of this operator (whether a message is given to the trader or not), after its execution the control will be passed to the next operator 'if-else':

The consecutive execution of both operators results in the possibility to perform both conditional tests and, finally, to solve the problem. While the program solves the task in full, this solution cannot be considered as absolutely correct. Please note a very important detail: The second conditional test will be executed regardless of the results obtained at testing in the first block. The second block will be executed, even in the case of the price exceeding the first level.

It should be noted here, that one of the important objectives pursued by the programmer when writing his or her programs is algorithm optimization. The above examples are just a demonstration, so they represent a short and, respectively, quickly executed program. Normally, a program intended to be used in practice is much larger. It can process the values of hundreds of variables, use multiple tests, each being executed within a certain amount of time. All this may result in the risk of that the duration of working of the special function start() may exceed the tick gaps. This will mean that some ticks may remain unprocessed. This is, of course, an extremely undesirable situation, and the programmer must do his or her best in order to prevent it. One of the techniques allowing to to reduce the time of the program execution is algorithm optimization.

Let's consider the latest example once again, this time in terms of resources saving. For example, what is the reason for asking "Is the price below the preset level?" in the second block, if the testing of the first block has already detected that the price is above the upper level? It is clear that, in this case, the price cannot be below the lower level, so there is no need to make a conditional test in the second block (nor to execute the set of operators in this block).

Solution 2 of Problem 10

Taking the above reasoning into account, let's consider the following, optimized algorithm:

According the algorithm shown in the above block diagram, no redundant operations will be executed in the program. After the preparatory calculations, the program will test whether The price is above the preset level . If yes, the program displays the corresponding message to the trader and passes the control to Subsequent Calculations , whereas the second condition ( Is the price below the preset level ?) is not tested. Only if the price hasn't turned out to be above the upper level (the answer is No ), the control is passed to the second block where the necessary conditional test is performed. If the price turns out to be below the lower level, the corresponding message will be displayed to the trader. If not, the control will be passed to the further calculations. It is obvious that, if the program works according this algorithm, no redundant actions are performed, which results in considerable saving of resources.

The programmed implementation of this algorithm implies the use of the nested operator 'if-else' ( twoleveloptim.mq4 ):

Please note this block of calculations:

The operator 'if-else', in which the second condition is tested, is a component of the first operator 'if-else' that tests the first condition. Nested operators are widely used in the programming practice. This is often reasonable and, in some cases, the only possible solution. Of course, instead of the function Alert(), real programs can use other functions or operators performing various useful actions.

A complex expression can also be used as a condition in the operator 'if-else'.

The statement of this problem is similar to that of Problem 10. The difference consists in that, in this case, we are not interested in the direction of the price movement - higher or lower than the predefined range. According to the problem situation, we have to know only the fact itself: Is the price within or outside the range? We can use the same text for the message to be displayed.

Here, like in the preceding solutions, it is necessary to check the price status as related to two levels - the upper one and the lower one. We have rejected the solution algorithm shown in Fig. 38 as non-efficient. So, according to the above reasoning, we can propose the following solution:

However, there is no need to use this algorithm. The diagram demonstrates that the algorithm implies the usage of the same block of messages at different points in the program. The program lines will be repeated, notwithstanding that the execution of them will result in producing the same messages. In this case, it would be much more efficient to use the only one operator 'if-else' with a complex condition:

The code of the program that implements this algorithm is as follows ( compoundcondition.mq4 ):

The key insight of this program solution is the use of complex condition in the operator 'if-else':

Simply stated, this condition is as follows: If the value of variable Price exceeds that of variable Level_1, or the value of variable Price is less than that of variable Level_2, the program must execute the body of the operator 'if-else'. It is allowed to use logical operations ( && , || and ! ) when composing the conditions of the operator 'if-else', they are widely used in the programming practice (see Boolean (Logical) Operations ).

When solving other problems, you may need to compose even more complex conditions, which makes no question, too. Some expressions, including the nested ones, can be enclosed in parentheses. For example, you may use the following expression as a condition in the operator 'if-else':

Thus, MQL4 opens up great opportunities to use the operators 'if-else': they can be nested, they can contain nested structures, they can use simple and complex test conditions, which results in the possibility to compose simple and complex programs with branching algorithms.

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Elektrostal , Moscow Oblast, Russia

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