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From: Alf-Ivar Holm <alfh@ifi.uio.no>
Newsgroups: comp.lang.beta
Subject: Mantatory argument
Date: 11 Jun 1997 08:24:22 +0200
Organization: The Department of Informatics, University of Oslo, Norway
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I have a library with some functions.  These functions does only
provide something useful if given an argument.  If I, by mistake,
don't assign any values to these functions, the program continues, but
the value(s) produces by the functions may break something else later
on.

Two problems: 

	1) The error is not catched where it occurred, and
	2) The error is not found before run-time.

Problem 1) may by fixed by adding something extra to each function
that give a warning or error at runtime if the functions are not
called with an argument.  Something like:

	myFunc:
	(# in, out: @integer;
   	   entered: @boolean;
   	enter (# enter in do true->entered #)
   	do (if not(entered) then notification(# ... #) else ... if);
	exit out
	#);

This is still no remedy for problem 2).  I have to wait for the
erroneous statement to occur run-time.  What I would like were some
kind of construct that would let me say that some patterns must be
assigned values.  It may be a bit non-Beta-ish to prevent patterns from
being used as any evaluation type.  OTOH, Beta does catch a lot of
errors compile-time, and this seems to be another case where it would
not be too hard for the compiler to find the error, given some
indication that the pattern must evaluate it's enter part.

Is it only me who would like this?  Have I missed something?

	Affi