Switch operator

Overview

The switch operator in MQL4 provides multi-way branching. It evaluates an expression and compares its value against a series of constant case labels. Control is transferred to the code block associated with the first matching case.

Syntax

switch(expression)
{
  case constant:
    operators
  case constant:
    operators
    ...
  default:
    operators
}

Expression Requirements

The expression within the switch() must be of an integer type.

Case Labels

Each case label must be followed by a constant value.

Constants can be integer constants, literal constants, or constant expressions.

Constant expressions cannot contain variables or function calls.

Constant expressions are evaluated during compilation.

No two constants within a single switch operator can have the same value.

Default Case

The default label is optional.

If no case constant matches the expression value and a default label exists, control transfers to the default block.

If no match is found and default is absent, no actions are executed.

Execution Flow

When a case label matches the expression, the associated operators are executed.

Execution continues sequentially into subsequent case blocks (fall-through) unless a break operator is encountered.

The break operator terminates the switch statement execution.

This fall-through behavior allows binding a sequence of operators to multiple case variants.

Constraints

Duplicate constants within a single switch statement are not allowed.

Constant expressions are evaluated at compile time.

Related Concepts

[Break Operator](/basis/operators/break)

[Integer Types](/basis/types/integer/integertypes)

Examples

// Example 1: Basic switch with break
int x = 'A';
switch(x)
  {
   case 'A':
     Print("CASE A");
     break;
   case 'B':
   case 'C':
     Print("CASE B or C");
     break;
   default:
     Print("NOT A, B or C");
     break;
  }// Example 2: Fall-through and default behavior
string res = "";
int i = 0;
switch(i)
  {
   case 1:
     res = i;
     break;
   default:
     res = "default";
     break;
   case 2:
     res = i;
     break;
   case 3:
     res = i;
     break;
  }
Print(res); // Output: default

Platform Support

MQL4 Language

SMOLDOC

Switch Operator