[Jprogramming] Permutations of a sort.

[Roger Hui]

> NB. Why doesn't something like this work:
> NB. rs=. (1) ri}&><bs

It doesn't work because the parse is
   rs=. (1) (ri})&><bs
and it parses like that because } is an adverb.



----- Original Message -----
From: Devon McCormick <devonmcc at gmail.com>
Date: Tuesday, August 28, 2007 4:56
Subject: Re: [Jprogramming] Permutations of a sort.
To: Programming forum <programming at jsoftware.com>

> Roger's method is undoubtedly better but is something like this 
> suitable?
>    ri=. 28?~&.>1000$4
>    3{.ri
> +----------------------------+
> ¦22 1 4 7¦2 27 11 8¦27 26 8 3¦
> +----------------------------+
>    putin1s=: 4 : '1 x}y'
> NB. Why doesn't something like this work:
> NB. rs=. (1) ri}&><bs
> NB. ?
>    $rs=. ri putin1s&><28$0
> 1000 28
>    4*./ . =+/"1 rs
> 1
>    $~.rs
> 984 28
> NB. 984 unique
> 
> NB. Could also do this (slightyly faster):
>    $rs2=. (1) (ri,~&.>&>i.#ri)}1000 28$0
> 1000 28
>    rs2-:rs
> 1
> 
> 
> On 8/27/07, Ralph G Selfridge <selfrid at cns.ufl.edu> wrote:
> >
> > Here's my problem. I have a binary string, potentially long, 
> in my case
> > 28. I need to get all binary strings with a specified number 
> of 1s. I
> > doubt
> > I can get them all at once, too many, so how do I get from one 
> to the
> > next?
> >
> > What next means is irrelvant, just so I get them with no 
> duplicates if I
> > run long emough.
> >
> > While I have an answer, I'm curious to see if there is a 
> better way.
> >
> >
> > Ralph S