Call of function in ST

Syntax

function-name();
 
function-name 
  (input_1:=x1,input_2:=x2,...,input_n:=xn,
  output_1=>y1,output_2=>y2,...,output_n=>yn);

Meaning

formal call of the →function (= formal function →call) without or with parameter list
The call of a user function declared by you (e.g. Simple2) and of a system function (e.g. the IEC-block AND) is done with the same syntax.

No check of recursions

Recursions for →functions and →methods are not forbidden or checked by logi.CAD 3 . Nevertheless, do not call a function/method from within itself and avoid 2 (or more) functions/methods calling each other (= mutual recursion) within your application.
Mind that recursions of functions/methods might cause unexpected results when your application is executed. For example, the application might be executed in an infinite loop and/or the →runtime system might not respond anymore.

This parameter list of a formal →call may contain the following elements:

→assignments to →input variables (incl. to input EN)
The expression on the right side of the assignment operator ":=" in the assignments to input variables may be one of the constructs as listed under Assignment.
assignments to →in-out variables
The expression on the right side of the assignment operator ":=" in the assignments to in-out variables may be just a construct which might be on the left side of the assignment operator ":=" as well.
assignments of →output variables (incl. to output ENO)
The expression on the right side of the assignment operator "=>" in the assignments of output variables may be a declared →variable (e.g. result) of a fitting →data type.

As alternatives, you can use the following variants for the call:

non-formal call
The parameter list must contain the same number of input variables, in exactly the same order and of fitting data types as given in the declaration , except the execution control parameters EN and ENO.
Example: Inst2 (10,20,T#3ms); – This non-formal call is equivalent to the formal call: Inst2 (EN := TRUE,IN1:=10,IN2 := 20,T1 := T#3ms, OUT => result);

incomplete parameter list of formal call
You can omit input variables and output variables within the parameter list. Omitted input variables get the default →initial value. See the examples below.
Special behavior: In case of extensible functions (such as the AND block), input variables after the top one specified are not considered for the functionality of the block. Hence, these input variables do not get the default initial value (see example below) .

The FAQ article "When to use a formal call? When to use a non-formal call?" lists a table when to use formal call vs. non-formal call.

Example

Simple1();
Simple2(IN1:=10, IN2 :=20, T1 := T#3ms, OUT => result);  
AND(IN1:=TRUE, IN2:=FALSE);

Examples for incomplete parameter list of formal call for a function:

Syntax	Meaning
`FUNCTION fun1 : INT` `VAR_INPUT` `i1 : INT :=` `7;` `i2 : INT :=` `8;` `END_VAR` `END_FUNCTION`	declaration of the function `fun1` declaration of the variables `i1` and `i2` with initial values
`FUNCTION fun2 : INT` `fun2:=22;` `END_FUNCTION`	declaration of the function `fun2` (with the result value '`22`')
`fun1();`	call of the function `fun1` without parameter list `fun1` gets the initial value `7` for `i1` and the initial value `8` for `i2`.
`fun1(i2:=3);`	call of the function `fun1` with incomplete parameter list `fun1` gets the initial value `7` for `i1` and the assigned value `3` for `i2`.
`fun1(i2:=fun2());`	call of the function `fun1` with incomplete parameter list `fun1` gets the initial value `7` for `i1` and the return value `22` (of `fun2`) for `i2`.
`fun1(i2:=fun2(EN:=FALSE));`	call of the function `fun1` with incomplete parameter list `fun1` gets the initial value `7` for `i1` and the initial value `8` for `i2`. Explanation: Because of `EN := FALSE`, `fun2` is not called. Hence, `i2` is supplied with the initial value. See "Assignments in ST" for detailed information on the behavior of calls containing an assignment to the input `EN`.

Examples for incomplete parameter list of formal call for the extensible AND block:

Syntax	Meaning
`AND();`	call of the function `AND` without parameter list This call is highlighted as faulty. Assignments to the first 2 inputs of the `AND` block are required.
`AND(IN2:=TRUE);`	call of the function `AND` with incomplete parameter list The value `TRUE` is assigned to `IN2`. The omitted input variable before `IN2` (hence: `IN1`) gets the default initial value `FALSE`. The omitted input variables after `IN2` (hence: `IN3` to `IN16`) are not considered for the functionality of `AND` .
`AND(IN1:=TRUE,IN10:=TRUE);`	call of the function `AND` with incomplete parameter list The value `TRUE` is assigned to `IN2` and `IN10`. The omitted input variables before `IN10` (hence: `IN2` to `IN9`) get the default initial value `FALSE`. The omitted input variables after `IN10` (hence: `IN11` to `IN16`) are not considered for the functionality of `AND` .