Function calling

phateee

Hello, I am a beginner in programming.I try to make procedure with parametr VAR or INOUT and compiler write me error. I think, that calling procedure with VAR or INOUT is something as pointer in language C/C++. For example:

MODULE A PROC routine(VAR num u)

    ...

   ENDPROC

PROC main()

  VAR num x;

   routine(x);

ENDPROC

ENDMODULEAnd compiler write: Argument error(124): Argument for 'VAR' parameter x is not variable reference or is read only 

Thank you for your advice    

Henrik Berlin

Try this instead:

[CODE]MODULE A

    PROC routine(INOUT num u)
        u:=2*u;
    ENDPROC

    PROC main()
        VAR num x:=1;
        TPWrite "Before routine: x = "Num:=x;
        routine x;
        TPWrite "After routine:  x = "Num:=x;
    ENDPROC

ENDMODULE[/CODE]

You can see the result in the Operator panel below:

Henrik Berlin

The RAPID Overview manual contains a description of INOUT, see
http://www.scribd.com/doc/71173119/Rapid-Overview-Manual#page=112

Thomas J

The reason you received the above message is because "routine(x)" implies a functin with a return value - the correct use of your format is

 

x:=routine(x); where routine is defined as a funtion with a return value.

 

    FUNC num routine(num u)
        RETURN 2*u;
    ENDFUNC

 

The instruction call syntax when passing variables or parameters is "routine x;" without ()

functin call syntax is "num:=routine(num);". with ()

 

Whenever you use the parentheses () RAPID interprets it as passing parameters to a function that will return a value.

 

To understand the difference please read the Introduction to RAPID section

"RAPID instructions and functions"

A RAPID function is similar to an instruction but returns a value
Since the function returns a value, the result of the function can be assigned to a variable. The arguments in a function call are written inside parenthesis and are separated with commas.

 

An instruction call looks like a procedure call with the instruction name followed by argument values not enclosed in parnthesis.

 

Hope this helps...