Array with variable length

In function blocks, functions or methods, arrays with variable length can be declared in the declaration section VAR_IN_OUT. The operators LOWER_BOUND and UPPER_BOUND can be used to determine the index limits of the array that is actually used at runtime. LOWER_BOUND returns the lower limit, UPPER_BOUND returns the upper limit.

	Only statically declared arrays may be passed to an array with variable length. Dynamic arrays created using the __NEW operator must not be passed.

Syntax

Declaration of a one-dimensional array with variable length

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

<variable name>

Array name

Sample: aCounter

<data type>

Data type of the element:

Elementary data type
User-defined data type
Function block

Note: References and pointers to BIT variables are invalid declarations, as are array components with the base type BIT.

<initialization>

Initial values of the array (optional)

Declaration of a multi-dimensional array with variable length

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

<variable name>

Array name

Sample: aCounter

ARRAY[*, *]

Declaration of a two-dimensional array of variable length

Formally, an asterisk stands for each dimension of variable length. The dimensions are separated by commas. Any number of dimensions of variable length are permitted.

Syntax of the operators for limit index calculation

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

Sample

The function AddValues adds the integer values of the array elements and returns the calculated sum as the result. The sum is calculated over all array elements present at runtime. Since 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. Arrays with different fixed lengths can be passed to this addition function.

FUNCTION AddValues : DINT;
VAR_IN_OUT
    aData  : ARRAY [*] OF INT;
END_VAR
VAR
    nIdx   : DINT;
    nSum   : DINT;
END_VAR

nSum := 0;
 
FOR nIdx := LOWER_BOUND(aData,1) TO UPPER_BOUND(aData,1) DO
    nSum := nSum + aData[nIdx];
END_FOR;

AddValues := nSum;