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From: "Tim Behrendsen" <tim@airshields.com>
Subject: Re: What's the best language to start with? [was: Re: Should I learn
 C or Pascal?]
Date: 1996/08/09
Message-ID: <01bb8609$59339140$87ee6fce@timpent.airshields.com>#1/1
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references: <31FBC584.4188@ivic.qc.ca>
 <01bb83ad$29c3cfa0$87ee6fce@timpent.airshields.com>
 <4u89c4$p7p@solutions.solon.com>
 <01bb83f5$923391e0$87ee6fce@timpent.airshields.com>
 <4uah1k$b2o@solutions.solon.com>
 <01bb853b$ca4c8e00$87ee6fce@timpent.airshields.com>
 <320b35a2.43769707@nntp.ix.netcom.com>
content-type: text/plain; charset=ISO-8859-1
organization: A-SIS
mime-version: 1.0
newsgroups: comp.lang.c,comp.lang.c++,comp.unix.programmer,comp.lang.ada
Date: 1996-08-09T00:00:00+00:00
List-Id: <comp.lang.ada>


Mike Rubenstein <miker3@ix.netcom.com> wrote in article
<320b35a2.43769707@nntp.ix.netcom.com>...
> "Tim Behrendsen" <tim@airshields.com> wrote:
> > Peter Seebach <seebs@solutions.solon.com> wrote in article
> > <4uah1k$b2o@solutions.solon.com>...
> > > In C, we write
> > > 
> > > 	int
> > > 	gcd(int x, int y) {
> > > 		if (y == 0)
> > > 			return x;
> > > 		return gcd(y, (x % y));
> > > 	}
> > > 
> > This is an interesting case, because it is somewhat inefficently
> > implemented.  If you're interested in speed, you would do...
> > 
> > int gcd(int x, int y) {
> >     int z;
> >     while (y != 0)
> >         z = y; y = x % y; x = z;
> >     return(y);
> > }
> 
> I don't understand how going into an infinite loop when y != 0
> improves the speed?  I guess I cut class that day.
> 
> Nor do I see how dividing by 0 (when y == 0) is an improvement?
> Perhaps I just cut too many classes.
> 
> Let's review the bidding.  Peter gives an algorithm.  You claim that
> knowledge of assembly helps one understand it better and produce a
> program that goes into an infinite loop if y is not zero and divides
> by 0 if y is zero.
> 
> Perhaps you meant
> 
> 	int gcd(int x, int y) {
> 	    int z;
> 	    while (y != 0)
> 	        { z = y; y = x % y; x = z; }
> 	    return(y);
> 	}
> 
> This avoids the infinite loop, but can be made even more efficient:
> 
> 	int gcd(int x, int y)
> 	{
> 	  return 0;
> 	}
> 
> Of course this isn't quite equivalent to Peter's function.
> 
> I guess, like Peter, I'm a little thick today.  Please explain again
> how knowing assembly language helps one understand algorithms?  I got
> a little confused when you transformed Peter's correct, but slightly
> inefficient function into an infinite loop.

Yes, you're right; my typo proves all my arguments false.  How can I
have been such a fool?

-- Tim Behrendsen (tim@airshields.com)