Ah, but solving such problems keeps me sane,
countering the bad effects of too much of gerunds
and f. and $. and other wickedness in the wicked
programming language.
No doubt
name=: x A. name
name=: (<i,j) C. name
will be required for efficiency even if
name=: p{name
will be available. For the last expression simply
generating p itself already costs O(n) space.
Regarding your last point:
http://www.jsoftware.com/jwiki/Essays/Symmetric_Array
----- Original Message -----
From: John Randall <[EMAIL PROTECTED]>
Date: Thursday, July 13, 2006 11:53 am
Subject: Re: [Jprogramming] special coding for stack operations
> Roger Hui wrote:
> > Once you assume that an operation is to be done
> > in place, swapping items at the front or at
> > the back are the same. There is free space
> > at the back and none at the front, but neither
> > matter if you are just swapping.
> >
> > As you'd indicated, in general the operation is:
> > name=: p{name
> > where p is a permutation and p=&#name .
>
> Roger:
>
> Maybe this is solving the problem in too much generality to be
> efficient.
>
> Postscript gets by with just two operations for this purpose: swap
> (which interchanges the top two elements on the stack) and roll (which
> does a cyclic shift of the top n elements). As you know, a
> transposition and a cycle of length n will generate the permutation
> group on n letters.
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