Array of variable length

In function blocks, functions, or methods, you can declare arrays of variable length in the ‎VAR_IN_OUT‎ declaration section.

The ‎LOWER_BOUND‎ and ‎UPPER_BOUND‎ operators are provided for determining the index limits of the actual used array at runtime.

Only statically declared arrays (not arrays generated by means of the operator ‎__NEW‎) may be passed to an array with variable length.

Syntax of the declaration of a one-dimensional array of variable length

<variable name> :  ARRAY[*] OF <data type> := <initialization> ;

‎<variable name>‎

Name of the array

Example: ‎aMyVariableArray ‎

‎<data type>‎

Data type of an element:

Elementary data type
User-defined data type
Function block

‎<initialization>‎

Optional

Initial values for the array of arrays

Syntax of the declaration of a multi-dimensional array of variable length

<variable name> :  ARRAY[*, *] OF <data type> := <initialization> ;

‎<variable name>‎

Name of the array

Example: ‎aMyVariableArray ‎

‎ARRAY[*, *]‎

Declaration for a two-dimensional array of variable length

Formally, an asterisk stands for each dimension of variable length. The dimensions are comma-separated.

NOTE:

Any number of dimensions of variable length are permitted.

Syntax of the operators for calculating the limit index

LOWER_BOUND( <variable name> , <dimension number> )
UPPER_BOUND( <variable name> , <dimension number> )

Example

The ‎SUM‎ function adds the integer values of the array elements and returns the calculated sum as a result. The sum is calculated across all array elements available at runtime. As the actual number of array elements will only be known at runtime, the local variable is declared as a one-dimensional array of variable length.

FUNCTION SUM: INT;
VAR_IN_OUT
    aiData : ARRAY[*] OF INT;
END_VAR
VAR
    diCounter : DINT;
    iResult : INT;
END_VAR

iResult := 0;
FOR diCounter := LOWER_BOUND(aiData, 1) TO UPPER_BOUND(aiData, 1) DO // Calculates the length of the current array
    iResult := iResult + aiData[diCounter];
END_FOR;
SUM := iResult;