Reader's Letters - Jim Owen

"I've discovered something that might be of interest to some AREV programmers regarding the calling of homemade functions. I had a function called SPC which padded blank spaces onto a variable. For example

        X = 65
        Y = SPC(X,5,"R")

would return Y = ' 65'. (Unsure as to why this differs from Y = 65 "R#5" - Ed).

However I discovered that this function also changed X!

I wanted my function to work like INT() which does not change the value of the variable inside the parens, only the value to the left of the '='.

RTI told me that the C-esque use of local vs global variables doesn't apply to RBASIC. One way to solve it was to make parameter 1 a literal string. This was done by calling the function thus

        X = 65
        Y = SPC(X:" ",5,"R")

Concatenating a null to the variable changes it to a string and does NOT change X. Another way around the problem was to immediately stuff some other variable with X on entering the function then operating on, and returning, this new variable.

Incidentally the INT() function is in assembler and avoids the problem altogether".

(Volume 2, Issue 6, Page 3)