Operator: OR_ELSE

The operator is an extension of the IEC 61131-3 standard.

The OR_ELSE operator is permitted only for programming in structured text: OR operation of BOOL and BIT operands with short-circuit evaluation. This means:

When at least one of the operands yields TRUE, the result of the operation also yields TRUE; otherwise FALSE.

In contrast to using the OR IEC operator, for OR_ELSE the expressions on all other operators are not evaluated as soon as one of the operands is evaluated as TRUE.

VAR
        bEver: BOOL;
        bX: BOOL;
        dw: DWORD := 16#000000FF;
END_VAR

bEver := FALSE;
bX := dw.8 OR_ELSE dw.1 OR_ELSE (bEver := TRUE);