Path: utzoo!attcan!uunet!husc6!uwvax!oddjob!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.fortran
Subject: Re: Fortran versus C for numerical analysis
Message-ID: <13547@mimsy.UUCP>
Date: 14 Sep 88 03:28:50 GMT
References: <410@marob.MASA.COM> <3445@lanl.gov> <183@djs.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 40

In article <183@djs.UUCP> samperi@djs.UUCP (Dominick Samperi) writes:
>The emphasis on _can_ is important here ....

Indeed.

>[some features] might be classified ... as "advanced" features
>of the language, and avoided entirely in numerical applications.

Alas, unless there were some way to signal to the compiler that this
were the case, or unless it were obvious, it would not help the
compiler generate better code.  (Fortunately, what is `obvious' is
growing by leaps and bounds in compiler technology.  Cross-module
optimisation is no longer considered `too hard'.  I predict that decent
alias detection will soon not be considered `too hard' either.  [Never
mind that it is in some sense impossible: so is loop optimisation, in
the presense of irreducible flow graphs, yet compilers do that today.])

>	while(*dest++ = *source++) ;
>
>could be written like this instead:
>
>	i = 0 ;
>	while(source[i] != 0)
>	{
>		dest[i] = source[i] ;
>		i = i + 1 ;
>	}
>	dest[i] = 0 ;

Any half-decent optimiser should have no trouble converting the former
to the latter (with `source += i, dest += i' added).  (This assumes
that the latter is more efficient.  Typically optimisers have had to
convert the latter to the former.)

I do suggest, though, that no one use `i = i + 1' to increment.  If you
dislike `++', use `i += 1'.  When you mean `add one to i', why not *say*
it?
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris