Function calling

RobotStudio
1

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

ENDMODULE

And compiler write:

Argument error(124): Argument for ‘VAR’ parameter x is not variable reference or is read only
Thank you for your advice

2

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:

3

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

4

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…