Attribute 'strict'

The attribute 'strict' results in compile errors occur in the following cases:

1. Arithmetic operation with variables of the enumeration type
2. Assignment of a constant value, which is not an enumeration value, to a variable of the enumeration type
   (although it is recommended to assign only components of an enumeration type to a variable of that enumeration type)
3. Assigning a non-constant variable – declared with a data type other than the enumeration type – to a variable of the enumeration type.
   (If the right-hand side of the assignment is not a constant, then the data types of the right- and left-hand sides must be the same and must therefore match the enumeration type.)

Syntax: {attribute 'strict'}

Insertion location: Line above the TYPE definition

Examples

Enumeration E_Colors:

{attribute 'qualified_only'}
{attribute 'strict'}
TYPE E_Colors :
(
    eRed    := 0,
    eGreen  := 1,
    eBlue   := 2
);
END_TYPE

Program MAIN:

PROGRAM MAIN
VAR CONSTANT
    c2      : INT := 2;
END_VAR
VAR
    e1, e2  : E_Colors;
    nVar    : INT;
END_VAR

// Regel 1
e1 := e1 + 1;  // NOK: Arithmetische Operation nicht erlaubt 
 
// Regel 2
e1 := 2;       // OK: Wert 2 ist im Enum definiert
e1 := c2;      // OK: Wert 2 ist im Enum definiert
e1 := 3;       // NOK: Wert 3 ist nicht im Enum definiert
 
// Regel 3
e1 := e2;      // OK: Datentyp stimmen überein
e1 := nVar;    // NOK: Datentypen stimmen nicht überein