Function Variables

[Ben624]

Can anyone tell me why I can't pass a discrete value to a user-defined procedure or function? For instance, I have written the following function to set minimum and maximum allowable values in a dialog field:

PROCEDURE LimitInput(VAR field : INTEGER; min, max : REAL);

VAR

fldInput : REAL;

TxtOK : BOOLEAN;

BEGIN

TxtOK := GetEditInteger(dlogID,field,fldInput);

IF fldInput > max THEN

setEditInteger(dlogID,field,max);

IF fldInput < min THEN

setEditInteger(dlogID,field,min);

END;

Why can't I use this by specifying the min and max when I call the procedure? eg: LimitInput(kLED1, 0, 35). If I try this, the compiler tells me that I can only pass variables to the procedure, not discrete values. Is that really true? Do I need to declare variables strictly to pass values to my procedure? I can pass values directly to vectorScript's native functions and procedures. What makes mine different?

Thanks!

Ben

[Pat Stanford]

By putting the Var at the beginning of the list of parameters, you are defining them all as variables. That means that you can't pass a discrete value to them. Put the variable parameters at the end of the list.

Procedure LimitInput(min,Max:Real; Var field:Integer);

Pat

[Miguel Barrera]

Ben,

You are passing kLED1, which seems like a constant, to the procedure and in your declaration the first argument "field" is a variable. You need to pass a variable to the procedure such as:

VAR

varInt: INTEGER;

BEGIN

........

varInt:= kLED1;

LimitInput(varInt,0,35);

........

END;

or change the declaration to:

PROCEDURE LimitInput(field : INTEGER; min, max : REAL);

[Ben624]

I see. thank you both. I thought the VAR was required in the function definition. Thanks again!

Ben

[MullinRJ]

By putting the Var at the beginning of the list of parameters, you are defining them all as variables. That means that you can't pass a discrete value to them. Put the variable parameters at the end of the list.

Procedure LimitInput(min,Max:Real; Var field:Integer);

Pat, that is only true if the parameters are all the same type and declared in the same parameter group.

eg. procedure XYZ(var A, B, C :Integer);?????{ all are VARs }

eg. procedure XYZ(var A :Integer; B, C :Integer);?????{ only A is a VAR }

but I do it as you do with the VARs at the end, as a convention.

eg. procedure XYZ(B, C :Integer; var A :Integer);?????{ input in the front, answers in the back }

I think it looks better.

I thought the VAR was required in the function definition. Thanks again!

It is only required if you want the function/procedure to return any modifications it made to your variable. Miguel is right, you cannot pass a constant value to a VAR parameter. The procedure has nowhere to put the new value on return.

One other pitfall that I often run into and is somewhat tricky to catch, but I'm getting faster with repeat infractions...

When you write two functions/procedures and one calls the other, if the other one returns a VAR parameter then it MUST be a VAR in the first.

eg.

???procedure XYZ(var A :Integer);

...

???procedure ABC(B :Integer);

???Begin

??????XYZ (B);?????{ will not work as B is not a VAR parameter and XYZ is expecting one }

???End; { ABC }

rather write:

???procedure ABC(var B :Integer);?????{ needs to be a VAR if it will be passed to another procedure }

???Begin

??????XYZ (B);?????{ now it will not work }

???End;???{ ABC }

If you write enough code, you will be cursed with the same message you got earlier, but it will be a little harder to track down. Hopefully you'll not spend as much time as I have in the past looking for the cause.

Raymond