Re: GNAT messages and the not operator (pitfall alert!)

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

Matthew said

  Are you sure?  My understanding is that "and" and "or" have equal
  precedence, and that Ada *requires* the use of parens to force to
  programmer to state his intent.

Well I can't really see what sense it makes to say they have the same
precedence when they cannot be mixed, but yes indeed, parens are
required.

  Please, please, if you need to leave a loop early, then use "exit when..."
  or return.  I've often seen code (even in software engineering texts that
  use Ada examples) that sets a loop flag to false, that in turn gets tested
  at the top of the (while) loop.  This is clearly a misuse of the language
  and a violation of all the principles of programming as a _human_ activity,
  as you've just doubled the number of states you have to test!

This is an arguable point. A loop with a goto that terminates it early (an
exit is a form of goto), has the disadvantage that there is no clear
precondition for the loop. I am not necessarily disagreeing, just saying
that this is a trickier issue that you suggest.