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ST Expressions dl-permalink__symbolPermalink

An expression is a construct that returns a value following its evaluation.

Expressions consist of operators and operands. In ⮫ Extended Structured Text (ExST), ⮫ Extended Structured Text (ExST), ⮫ Extended Structured Text (ExST), you can also use assignments as expressions. An operand can be a constant, variable, function call, or another expression.

Special ST expressions are also:

  • Access to

    • Elements of array variables

    • Components of a structure variable

    • Variables of a function block instance or a program

  • Method call

Examples

‎2014‎

Constant, literal

‎ivar‎

Variable

‎fct(a,b)‎

Function call

‎(x*y)/z‎

Expression

‎real_var2 := int.var;‎

In ExST: Assignment
  • Evaluation of expressions