Re: constraint-errors

[dewar@schonberg.cs.nyu.edu (Robert Dewar)]

">Can someone please give me some general advice on what causes
>constraint-errors?  For 2 years I have been plagued by them every time I
>try to do any programming at all in Ada.  The only way I get by is by
>continuing to try different things until something finally works, but I
>never really understand what caused the crash in the first place."


This kind of trial-and-error programming style is really worrisome, and
sometimes I am afraid far too much of it goes on in academic environments.
Trial and error is never a susbtitute for understanding. The real trouble
with programming by T&E is that it does not scale up at all.

But in academic environments, all too often people are working on small
programs and can get them to work by a mixture of T&E and asking for
help constantly and just taking the advice without understanding it (that's
something to think about the next time you feel like answering some
student doing Ada homework who asks for help on CLA!)

My favorite experience of this kind was from many years ago. A studen
who had supposedly complted several programming assignments came to me
with a listing and could not understand the error message:

   ***** else with no preceding if

I explained that indeed the program had an else with no if in sight

"Oh", said the student, "Should I add an if statement somewhere?"

:-)