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From: hebert@prism.uvsq.fr (Renaud HEBERT)
Newsgroups: comp.lang.ada
Subject: Re: "Subtract C, add Ada"
Date: 20 Jan 1995 13:22:17 GMT
Organization: Laboratoire PRiSM - Universite de Versailles-St Quentin - France
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Date: 1995-01-20T13:22:17+00:00
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In article <3fo2ot$su2@miranda.gmrc.gecm.com>, bill@valiant (R.A.L Williams) writes:
|> 
|> In article <3f5s92$3id@info.epfl.ch> you wrote:
|> : In article <3f4mbe$rud@cronkite.seas.gwu.edu>, dobrien@seas.gwu.edu (David O'Brien) writes:
|> : |> R.A.L Williams (bill@valiant) wrote:
|> : |> : My experience of writing software and running software projects in C
|> : |> : highlights four common low-level C errors:
|> : |> :   1. = instead of == and vice versa
|> : |> 
|> : |> I have to wonder.  What if C defined the logical equals operator to be
|> : |> "=" and the assignment operator to be ":=" just like Ada, Algol, Pascal,
|> : |> Modula-x, etc?  Would this error still exist???
|> 
|> : The problem is in the language definition, not in the choic of symbols.
|> : C is one of the rare language I use to allow having an assignment after 
|> : the if statement.  All other languages only allow for a boolean test.
|> 
|> : I never saw a good reason for allowing this.
|> 
|> I think there are three reasons:
|>  1. It allows your code to be more compact. Many people think this is
|>     a disadvantage, and so it is if the code will be read by comparative
|>     novices, but it can improve readability to C experts who are 
|>     expecting such tricks.
|> 
|>     NB DONT confuse compactness with poor layout! I find that, for example:
|> 
|>        while ((c = getchar()) == ' ')
|>        {
|>           /* count spaces */
|>        }
|> 
|>     is clearer than the 'expanded' alternative (to *me* :-).
|> 
|>  2. All expressions in C have a value. Conditional tests succeed on 
|>     non-zero and fail on zero. Therefore, to maintain orthogonality, 
|>     as far as possible, there is no reason to exclude an assignment 
|>     expression from a condition.
|>    
|>  3. Finally, I suspect, this can simplify the optimisation algorithms 
|>     in the compiler.
|> 
|> Personally, the lack of this sort of compactness in Ada, and things like
|> pre- and post-increment/decrement are one of my minor gripes about the
|> language. OK, its no big thing to write:
|> 
|>     P(I) := Q(I);
|>     I := I + 1;
|> 
|> instead of
|>  
|>     *p++ = *q++;
|> 
|> but I actually *do* find the C representation easier/better etc. (perhaps
|> I'm wierd?)

Even if I like C, I think that this ++ is ugly and I'm glad that there isn't such
a thing in Ada. On the other hand what do you think about the operators += *= ...
They make thing shorter AND easier to read, a += 5; means exactly add 5 to a.
So don't you think that these construct have their place in Ada.

|> 
|> : -- 
|> : Laurent Gasser (gasser@dma.epfl.ch)
|> : Computers do not solve problems, they execute solutions.
|> 
|> : I know very few ideas worth dying for, none is worth killing.
|> 
|> Very true, but quite a few are worth a pint in the pub.
|> 
|> Bill Williams
|> 

-- 
Renaud HEBERT		e-mail: Renaud.Hebert@prism.uvsq.fr