Re: [Haskell-cafe] Java or C to Haskell
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 <[EMAIL PROTECTED]> 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@haskell.org > From: Carajillu <[EMAIL PROTECTED]> > 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 <[EMAIL PROTECTED]> 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- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Java or C to Haskell
... 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@haskell.org > From: Carajillu <[EMAIL PROTECTED]> > 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 <[EMAIL PROTECTED]> 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 signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Java or C to Haskell
On Wed, Sep 20, 2006 at 07:20:23PM +1000, Donald Bruce Stewart wrote: > > comp l1 l2 = if l1 == l2 then True else False > > > > You never stop learning! > > andrea > > which you would just write as: > comp = (==) > > and then you'd just use == anyway :) this is why I came to love haskell: it remembers me when I was doing mathematics at the high school. The most challenging stuff, for me, was finding a way to simplifying expressions... It's just an endless chess game. Sending mails to this mailing list, I mean. Andrea ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Java or C to Haskell
Andrea Rossato <[EMAIL PROTECTED]> writes: > I forgot, obviously, that lists are an instance of the Eq class... > so, this is enough: > comp l1 l2 = if l1 == l2 then True else False Or why not: > comp l1 l2 = l1 == l2 Or simply: > comp = (==) :-) -k -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
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 <[EMAIL PROTECTED]> 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 > -- > If I haven't seen further, it is by standing in the footprints of giants > > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > -- View this message in context: http://www.nabble.com/Java-or-C-to-Haskell-tf2303820.html#a6404344 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Java or C to Haskell
That works good, but I have a problem with the return type, I forgot to
mention... can it be a [char]??
Donald Bruce Stewart wrote:
>
> crespi.albert:
>>
>> I'm trying to write in Haskell a function that in Java would be something
>> like this:
>>
>> char find_match (char[] l1, char[] l2, char e){
>> //l1 and l2 are not empty
>> int i = 0;
>> while (l2){
>> char aux = l2[i];
>> char[n] laux = l2;
>> while(laux){
>> int j = 0;
>> if(laux[j] = aux) laux[j] = e;
>> j++;
>> }
>> if compare (l1, laux) return aux;
>> else i++;
>> }
>> return '';
>> }
>
> Yikes!
>
>>
>> compare function just compares the two lists and return true if they are
>> equal, or false if they are not.
>> it is really a simple function, but I've been thinking about it a lot of
>> time and I can't get the goal. It works like this:
>>
>> 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)
>
> That's almost a spec there :)
>
> How about:
>
> import Data.List
>
> findMatch s t c
> | Just n <- elemIndex c s = Just (t !! n)
> | otherwise = Nothing
>
> Using it in GHCi:
>
>> findMatch "4*h&a" "4*5&a" 'h'
> Just '5'
>
>> findMatch "4*n&s" "4dhnn" 'k'
> Nothing
>
> -- Don
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Re: [Haskell-cafe] Java or C to Haskell
mailing_list: > On Wed, Sep 20, 2006 at 01:31:22AM -0700, Carajillu wrote: > > compare function just compares the two lists and return true if they are > > equal, or false if they are not. > > it is really a simple function, but I've been thinking about it a lot of > > time and I can't get the goal. > > I forgot, obviously, that lists are an instance of the Eq class... > so, this is enough: > comp l1 l2 = if l1 == l2 then True else False > > You never stop learning! > andrea which you would just write as: comp = (==) and then you'd just use == anyway :) -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Java or C to Haskell
wow, the simpliest ever! Andrea Rossato wrote: > > On Wed, Sep 20, 2006 at 01:31:22AM -0700, Carajillu wrote: >> compare function just compares the two lists and return true if they are >> equal, or false if they are not. >> it is really a simple function, but I've been thinking about it a lot of >> time and I can't get the goal. > > I forgot, obviously, that lists are an instance of the Eq class... > so, this is enough: > comp l1 l2 = if l1 == l2 then True else False > > You never stop learning! > andrea > ___ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > -- View this message in context: http://www.nabble.com/Java-or-C-to-Haskell-tf2303820.html#a6404305 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Java or C to Haskell
Carajillu <[EMAIL PROTECTED]> 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 -- If I haven't seen further, it is by standing in the footprints of giants ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Java or C to Haskell
On Wed, Sep 20, 2006 at 01:31:22AM -0700, Carajillu wrote: > compare function just compares the two lists and return true if they are > equal, or false if they are not. > it is really a simple function, but I've been thinking about it a lot of > time and I can't get the goal. I forgot, obviously, that lists are an instance of the Eq class... so, this is enough: comp l1 l2 = if l1 == l2 then True else False You never stop learning! andrea ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Java or C to Haskell
dons:
> crespi.albert:
> >
> > I'm trying to write in Haskell a function that in Java would be something
> > like this:
> >
> > char find_match (char[] l1, char[] l2, char e){
> > //l1 and l2 are not empty
> > int i = 0;
> > while (l2){
> > char aux = l2[i];
> > char[n] laux = l2;
> > while(laux){
> > int j = 0;
> > if(laux[j] = aux) laux[j] = e;
> > j++;
> > }
> > if compare (l1, laux) return aux;
> > else i++;
> > }
> > return '';
> > }
>
> Yikes!
>
> >
> > compare function just compares the two lists and return true if they are
> > equal, or false if they are not.
> > it is really a simple function, but I've been thinking about it a lot of
> > time and I can't get the goal. It works like this:
> >
> > 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)
>
> That's almost a spec there :)
Ah, I see I misread the spec :) Time for some tea.
-- Don
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Re: [Haskell-cafe] Java or C to Haskell
On Wed, Sep 20, 2006 at 01:31:22AM -0700, Carajillu wrote:
>
> I'm trying to write in Haskell a function that in Java would be something
> like this:
>
> char find_match (char[] l1, char[] l2, char e){
> //l1 and l2 are not empty
> int i = 0;
> while (l2){
> char aux = l2[i];
> char[n] laux = l2;
> while(laux){
> int j = 0;
> if(laux[j] = aux) laux[j] = e;
> j++;
> }
> if compare (l1, laux) return aux;
> else i++;
> }
> return '';
> }
>
> compare function just compares the two lists and return true if they are
> equal, or false if they are not.
I know that this is far too simple. But I'm simple minded:
comp [] [] = True
comp (x:xs) (y:ys) = if x == y then comp xs ys else False
andrea
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Re: [Haskell-cafe] Java or C to Haskell
crespi.albert:
>
> I'm trying to write in Haskell a function that in Java would be something
> like this:
>
> char find_match (char[] l1, char[] l2, char e){
> //l1 and l2 are not empty
> int i = 0;
> while (l2){
> char aux = l2[i];
> char[n] laux = l2;
> while(laux){
> int j = 0;
> if(laux[j] = aux) laux[j] = e;
> j++;
> }
> if compare (l1, laux) return aux;
> else i++;
> }
> return '';
> }
Yikes!
>
> compare function just compares the two lists and return true if they are
> equal, or false if they are not.
> it is really a simple function, but I've been thinking about it a lot of
> time and I can't get the goal. It works like this:
>
> 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)
That's almost a spec there :)
How about:
import Data.List
findMatch s t c
| Just n <- elemIndex c s = Just (t !! n)
| otherwise = Nothing
Using it in GHCi:
> findMatch "4*h&a" "4*5&a" 'h'
Just '5'
> findMatch "4*n&s" "4dhnn" 'k'
Nothing
-- Don
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