Calling sub programs

[leprechaun]

I apologize but apparently I have, still, not understood how calling cas and home programs can call each other....

I have made a cas program to extract the expression from a function. I found great help here:http://www.hpmuseum.org/forum/thread-3516.html

Now that is a cas program. I tried to make a normal program that does the same because having my tools in the toolbox instead of variable content feels better. No success. My old friend "unmatched control word" says hello again and again.
Well no poblem - i have the cas function that works. I'll use that. I thought.
My Goal is to write a wrapper for convenient function plotting. I was inspired by an other thread and don't like the way the prime acts.

First start simple. I thought. Show the expression which should be drawn later:

Code:


EXPORT plot(args)
BEGIN
 LOCAL expr:=CAS.expression(args); //tried with and without CAS.

 RETURN STRING(expr);
END;

Unmatch control word hello, again. Well I remember Han explaining that when home and cas Exchange data or call functions of the other part, their arguments are resolved if possible and therefore do harm. "pass them as strings" I thought. But I fail, again... I cannot get "f1" from the original parameter.

Code:


EXPORT plot(args)
BEGIN
 LOCAL expr:=STRING(args); //CAS.string Fails aswell
END;

How do I use my cas-function expression() from a home program. Or in my specific case: how do I deal with it