Re: MODS in subprocedures

["Joep Beckeringh" <joep@xxxxxxxxxxxxxxxxxxx>]

> What I am working on understanding now is the merits between passing the
> pointer to the subprocedure versus returning the pointer to the calling
> subprocedure.  For that matter, what are the merits of using a return
> argument at all?

The merits of using a return argument are in the fact that you can use the
result in an expression.  Something like EVAL a = your_function(b) or IF
your_function(a) > 3.  Moreover, you can pass the return argument to another
function, like EVAL a = function_1(function_2(b)).

As for the pointer issue: when you pass a pointer to a procedure, the caller
controls the storage.  When a procedure returns a pointer, the procedure is
responsible for the storage, but the caller has no control over this
storage.  The procedure might be in a different activation group; when it is
reclaimed, the pointer becomes invalid.  So, passing the pointer to the
procedure is safer.

Joep Beckeringh



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