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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: Equality operator overloading in ADA 83
Date: 1997/05/05
Message-ID: <dewar.862878406@merv>#1/1
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Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-05-05T00:00:00+00:00
List-Id: <comp.lang.ada>


Mats says

<<In
   case f(g(x)) is
      when a => ...
      when b => ...
   end case;

you see immediately, without having to read the whole statement, that a
decision is being made that depends only on the value of f(g(x)).
Moreover, if f(g(x)) is a long expression, you only have to write it
once. if ... elsif does not have these two advantages.>>

I can perfectly well live with

   declare
      fgx : constant integer := f (g (x));
   begin
      if    fgx = a then ...
      elsif fgx = b then ...
      end if;
   end;

Yup, it's a little bit longer, but it just does not seem worthwhile
confusing the case semantics and adding considerable complexity to
the language and its description just to save a few tokens in this
case.

Actually this example is a big bogus, since it is really implying that
the only possible values are a or b, so if the above case is what you
mean, and if you really mean to cover all cases, then the above code
is equivalent to

  if f(g(x)) = a then
      ...
  else -- = b
      ...
  end if;

which is actually shorter (8 tokens instead of 11)

I don't like introducing extra complexity in languages just for the sake
of a bit of syntactical sugar ...

A similar example arose during the 9X discussions, where

  raise x when ...

was proposed.
dp