[Jprogramming] Splitting an integer into its digits

[bill lam]

to get the oneliner, use the f. adverb eg
(#~ special) f.

digits should be used as rank 0, and the @ adjacent to digits should then
be changed @: otherwise fp1 and +/ would also become used as rank 0.

or you want a spoiler?

Сбт, 28 Авг 2010, Alex Gian писал(а):
> Hi all,
> 
> OK, based on the understanding I've gained so far, here and on the other
> thread (re filtering), I thought I'd try a couple of little tests, see
> how I get along.
> 
> I've got two here, the first is a quasi trivial programming challenge
> (it was originally given for programmable calculators) and is fairly
> easy in concept.  The second one is the so-called "happy numbers" which
> I found quite simple to do, but I may still ask for some style feedback.
> 
> First off, the "challenge".  It's quite simple in concept, and I know
> how to do all the separate bits in J, but I'm having trouble stringing
> it all coherently.  I get "length errors", which makes me suspect rank.
> 
> The challenge:
> We define a 'special' number as one which returns itself when subjected
> to the following operation:  first split it into its digits, then
> perform the following operation on each digit x:   x! + x 
> Then sum the result.
> Required to find all special numbers between 1 and 100000 (I think there
> are two)
> 
> Here's what I got so far.  Not nearly brave enough to put it on one line
> yet.
> 
> digits =. 10&#.inv  NB.  No probs here
> fp1 =. ! + ]        NB.  I think that's fine too
> spsum =. +/ @ fp1 @ digits  NB.  Works... BUT...
> special=. ]=spsum
> (#~ special) >:i.1000000  NB. That's the idea, but it's wrong
> 
> I think the problem is with spsum, above.
> it will not process arrays correctly, although it's fine with single
> numbers.
> 
> And if anyone feels like depriving me of sleep, please write down the
> single line expression...
> 
> 
> 
>    
> 
> 
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