> First, I should note that (if you're going for conciseness) that
> expression contains a token which can be eliminated with a fairly
> obvious rephrasing.
rpl2 =: ] - (0 ,~ -/)@[ {~ ] i.~ [EMAIL PROTECTED]
rpl2a=: ] - (-/ , 0:)@[ {~ [EMAIL PROTECTED] i. ]
Two tokens:
# ;: 5!:5 <'rpl2'
19
# ;: 5!:5 <'rpl2a'
17
----- Original Message -----
From: Raul Miller <[EMAIL PROTECTED]>
Date: Thursday, July 5, 2007 12:14
Subject: Re: [Jprogramming] Re: Replacement
To: Programming forum <[email protected]>
> On 7/5/07, david alis <[EMAIL PROTECTED]> wrote:
> > Raul's method of reducing the replacement problem
> > into simple arithmetic is a classic.
> >
> > rpl2=: ] - (0 ,~ -/)@[ {~ ] i.~ [EMAIL PROTECTED]
> >
> > It'd be nice to know when he first used it
>
> First, I should note that (if you're going for conciseness) that
> expression contains a token which can be eliminated with a fairly
> obvious rephrasing.
>
> Second, I used analogous mechanisms in APL back in the '90s
> (but my memory is not good enough for me to say much more than
> that).
>
> Third, I have frequently wished for an operation analogous to
> addition (1-to-1, with an identity element and an inverse operation)
> which worked across the full domain of J's verbs. But I
> have never
> been able to comfortably decide what other properties it should
> have for literals and boxes. But, even without an inverse
> and support
> for nothing beyond the identity operation, this could be useful
> (for example, assembling data in a list using two different
> mechanisms, using "zeros" (fills, presumably) as placeholders
> for elements coming from the other mechanism -- this hypothetical
> operation could then combine the two results.
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