[Jprogramming] Simple J

[Marc Simpson]

On Sat, Nov 12, 2011 at 2:13 AM, Kip Murray <km at math.uh.edu> wrote:
> Verb k is my version of f written in "Simple J" which uses trains and
> rank but no other conjunction.  The expected left argument is a string,
> right argument a list of boxed strings.
>
>    k =: ( ([: +/ E.) > )"1 0
>
>    'bc' k 'a bc def';'ab cde f';'abc d ef'  NB. Is 'bc' a substring?
> 1 0 1
>
>    '  ' k 'ab';'abc';'abcd'  NB. two spaces a substring?
> 0 0 0

Good stuff—but note that the following case is problematic,

   'bc' k 'ab';'bc';'bcd';'ad';'a'
|rank error: k
|   'bc'    k'ab';'bc';'bcd';'ad';'a'

In other words, padding with fill characters is a trade-off: on the
one hand incorrect results are yielded for whitespace tests, on the
other there are no length restrictions (length >= #x) placed on the
boxed strings.

When it's possible to use ;: as in Raul's example, the domain
restriction and whitespace issues are resolved,

   'bc' k ;:'ab bc bcd ad a'
0 1 1 0 0
   '  ' k ;:'ab bc bcd ad a'
0 0 0 0 0

-M