[Haskell-cafe] Java or C to Haskell

[Cale Gibbard]

How about something like this?

import Data.List

findMatch xs ys k = lookup k . concat $ zipWith zip (substrings xs)
(substrings ys)
    where substrings = nonempty . map (nonempty . inits) . tails
              where nonempty = filter (not . null)

On 20/09/06, Matthias Fischmann <fis at wiwi.hu-berlin.de> wrote:
>
> ...  and if you want to search strings not single characters:
>
> findmatch s t e = take m . drop n $ t
>     where
>     m' = length e
>     (n, m) = f 0 s
>     f i s | take m' s == e  = (i, m')
>           | null s          = (0, 0)
>           | otherwise       = f (i+1) (tail s)
>
> findmatch "asdfasdf" "asdfxvdf" "fas" == "fxv"
>
> (this one skips equality checks before *and* after the match.  feel
> free post the necessary modifications.  :)
>
> matthias
>
>
>
> On Wed, Sep 20, 2006 at 02:22:29AM -0700, Carajillu wrote:
> > To: haskell-cafe at haskell.org
> > From: Carajillu <crespi.albert at gmail.com>
> > Date: Wed, 20 Sep 2006 02:22:29 -0700 (PDT)
> > Subject: Re: [Haskell-cafe] Java or C to Haskell
> >
> >
> > Yes, they must be equal the whole way, I like this recursive solution :)
> >
> > Ketil Malde-3 wrote:
> > >
> > > Carajillu <crespi.albert at gmail.com> writes:
> > >
> > >> compare function just compares the two lists and return true if they are
> > >> equal, or false if they are not.
> > >
> > >> find_match "4*h&a" "4*5&a" 'h' ----> returns '5' (5 matches with the h)
> > >> find_match "4*n&s" "4dhnn" "k" ----> returns ''  (no match at all - lists
> > >> are different anyway)
> > >
> > > Must they be equal the whole way, or just up to the occurrence of the
> > > searched-for character?
> > >
> > >   find_match (x:xs) (y:ys) c | x==c = Just y
> > >                              | x/=y = Nothing
> > >                              | True = find_match xs ys c
> > >   find_match [] [] _ = Nothing
> > >
> > > Or, to check the whole list:
> > >
> > >   find_match (x:xs) (y:ys) c | x==c && xs == ys = Just y
> > >                              | x/=y = Nothing
> > >                              | True = find_match xs ys c
> > >   find_match [] [] _ = Nothing
> > >
> > > -k
>
>
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.1 (GNU/Linux)
>
> iD8DBQFFER17TXPx/Y0ym6oRAvNZAKCrLeJQxP0PjJAOz2KDi/S0hi7/ywCeMOfH
> XIOJJcMs9yFsg2IajkmHX7Y=
> =+bkI
> -----END PGP SIGNATURE-----
>
>
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