MQL4 Other Operations

Indexing ( [] )

**Purpose**: Accesses the i-th element of an array.

**Syntax**: array[index]

**Index Type**: Must be an integer.

**Dimensions**: Supports up to four dimensions.

**Indexing Range**: Each dimension is indexed from 0 to dimension_size - 1.

**Error Handling**: Accessing beyond array bounds results in a critical error and program termination.

**Example**: array[0] for the first element, array[49] for the last in a 50-element array.

Function Call ( () )

**Purpose**: Invokes a function with arguments.

**Syntax**: FunctionName(argument1, argument2, ..., argumentN)

**Arguments**: Can be constants, variables, or expressions of the corresponding type. Separated by commas.

**Evaluation Order**: Arguments x1, ..., xn are executed strictly in this order.

**Return Value**: The expression value is the function's return value. Void return types cannot be used in assignment operations.

Comma Operation ( , )

**Purpose**: Executes multiple expressions sequentially.

**Syntax**: expression1, expression2, ..., expressionN

**Evaluation Order**: Expressions are executed from left to right.

**Side Effects**: Side effects of left expressions are available before right expressions are calculated.

**Result**: The result type and value coincide with those of the rightmost expression.

**Usage**: Common in for loop initializers and update clauses.

**Example**: for(i=0, j=99; ...)

Dot Operator ( . )

**Purpose**: Direct access to public members of structures and classes.

**Syntax**: Variable_name_of_structure_type.Member_name

**Example**: st.sessionName = "Asian";

Scope Resolution Operation ( :: )

**Purpose**: Specifies the execution scope for functions, resolving ambiguity.

**Syntax**: [Scope_name]::FunctionName(parameters)

**Global Scope**: If Scope_name is omitted, the global scope is used.

**Function Search Order**: Class methods -> MQL4 functions -> User-defined global functions -> Imported functions.

**Class Member Definition**: Used to define class member functions: type Class_name::Function_name(parameters_description) { ... }

**Example**: ::Print(...) for global scope, kernel32::GetLastError() for imported DLL function.

sizeof Operation

**Purpose**: Determines the memory size of an identifier or data type.

**Syntax**: sizeof(expression)

**Expression**: Can be any identifier or type name (except void). Cannot be a bitfield or function name.

**Array Handling**:

* Static arrays: Returns the total size (elements * type size). * Dynamic arrays: Returns the size of the dynamic array object.

**Structure/Class Size**: Returns the actual memory size of the structure or class.

**Calculation**: Performed at the compilation stage.

**Example**: sizeof(str), sizeof(myStruct)