Suppose
c=: ?256
d=: 16+?16
e=: a.{~ c (d b.) i.256
NB. e is used as: map=: e {~ a. i. ]
Can you recover c and d given e? c and d are not
necessarily unique so it suffices to compute c1 and d1
such that e -: a.{~ c1 (d1 b.) i.256 .
----- Original Message -----
From: Roger Hui <[EMAIL PROTECTED]>
Date: Monday, September 24, 2007 18:17
Subject: Re: [Jprogramming] ASCII bytes to string
To: Programming forum <[email protected]>
> I'd forgotten that in J6.02, whose beta will be available soon,
> the phrase p {~ q i. ] where p and q are strings, is
> supported
> by special code. Exploiting this phrase:
>
> map=: (a.{~128 (23 b.) i.256) {~ a. i. ]
>
> scramble2=: 3 : 0
> (map read <y) write <y,'.scrambled'
> )
>
> ts 'scramble2 ''\junk\foo'''
> 0.0393609 4.1975e6
> ts 'scramble2 ''\junk\foo1'''
> 0.0396972 4.19763e6
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