Re: subroutines are bug factories was: Classic Traps -- I need yourinput!

Murphy, Mark wrote:

No, local variables do not make the code more bug prone because they are only applicable to the
subprocedure, and since a subprocedure only does a single thing, it isn't all that big. Therefore, a
subprocedure isn't terribly hard to read and understand. And since a subprocedure only does a single
thing, and has no side-effects, it is easy to reuse wherever it is needed; just like a BIF.

One gotcha with local variables: If you have procedure in a module with a global file, and the procedure does a READ or WRITE without a result data structure, then the I/O operation will use the global fields on the I or O specs. If you have defined local fields with the same names as the global fields, your procedure won't be able to see the values of the changed fields from the READ, or the unchanged global fields' values will get written out to the file.

Moral: If you want to do I/O to a global file in a procedure, don't define local variables with the same names as fields that appear on any I or O specs (in the compile listing).