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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: 1996/08/16
Message-ID: <01bb8b84$200baa80$87ee6fce@timpent.airshields.com>#1/1
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references: <31FBC584.4188@ivic.qc.ca>
 <01bb83f5$923391e0$87ee6fce@timpent.airshields.com>
 <4uah1k$b2o@solutions.solon.com>
 <01bb853b$ca4c8e00$87ee6fce@timpent.airshields.com>
 <4udb2o$7io@solutions.solon.com>
 <01bb8569$9910dca0$87ee6fce@timpent.airshields.com>
 <4urqam$r9u@goanna.cs.rmit.edu.au>
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newsgroups: comp.lang.c,comp.lang.c++,comp.unix.programmer,comp.lang.ada
Date: 1996-08-16T00:00:00+00:00
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Richard A. O'Keefe <ok@goanna.cs.rmit.edu.au> wrote in article
<4urqam$r9u@goanna.cs.rmit.edu.au>...
> 
> If you encounter any significant difference in speed between recursive
> and non-recursive quicksort, all that tells you is that it is time to
> change compilers.  Come to that, if you really cared about speed you
> wouldn't be using quicksort anyway.

Yes, but you can use the "get a better compiler" argument to
justify anything.  Real programs run on real computers using
real compilers.  The "Super-Duper Ivory Tower 9000 Compiler"
just doesn't exist.

> >If I implemented Quicksort in APL, say (which has direct
> >manipulation of arrays in one operation), 
> 
> Given the grade-up primitive, I can't think why anybody would _want_
> to implement quicksort in APL.

Well, I realize that APL has a built-in sort, but the point
was in learning quicksort through an implementation in APL.

> >the student would
> >not see the movement, because they would just see the computer
> >doing the array "in one fell swoop", but wouldn't really
> >experience the fact that the computer doesn't really do it
> >that way in reality.
> 
> Interestingly enough, the APL sorting primitive DOESN'T move the data
> at all.  It returns a permutation vector.  The APL idiom for sorting is
> 	X[.GradeUP X]
> where the necessary movement is quite visible.

But the reality is *not* visible.  What has the student really
learned?

-- Tim Behrendsen (tim@airshields.com)