Boolean operations - MQL4

MQL4 Boolean Operations

Logical Negation (!)

**Operand Type:** Arithmetic.

**Result:** TRUE (1) if operand is FALSE (0); FALSE (0) if operand is non-zero.

**Example:** if(!a) Print("not 'a'");

Logical Operation OR (||)

**Operands:** x, y.

**Result:** TRUE (1) if x or y is true (non-null). FALSE (0) otherwise.

**Example:** if(x<0 || x>=max_bars) Print("out of range");

Logical Operation AND (&&)

**Operands:** x, y.

**Result:** TRUE (1) if both x and y are true (non-null). FALSE (0) otherwise.

Brief Estimate of Boolean Operations

**Mechanism:** Short-circuit evaluation. Calculation terminates when the result can be definitively determined.

**&& Example:** If the left operand is FALSE, the right operand is not evaluated.

**|| Example:** If the left operand is TRUE, the right operand is not evaluated.

**Code Example for Brief Estimate:**

void OnStart() {
    // && example
    if(func_false() && func_true()) {
        Print("Operation &&: You will never see this expression");
    } else {
        Print("Operation &&: Result of the first expression is false, so the second wasn't calculated");
    }
    // || example
    if(!func_false() || !func_true()) {
        Print("Operation ||: Result of the first expression is true, so the second wasn't calculated");
    } else {
        Print("Operation ||: You will never see this expression");
    }
}
bool func_false() {
    Print("Function func_false()");
    return(false);
}bool func_true() {
    Print("Function func_true()");
    return(true);
}

**See also:**

[Precedence Rules](/basis/operations/rules)

[Operations of Relation](/basis/operations/relation)

[Bitwise Operations](/basis/operations/bit)