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*ha 4*5a 'h' returns '5' (5 matches with the h)
find_match 4*ns 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*ha 4*5a 'h'
Just '5'
findMatch 4*ns 4dhnn 'k'
Nothing
-- 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
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*ha 4*5a 'h' returns '5' (5 matches with the h)
find_match 4*ns 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: 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
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
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
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*ha 4*5a 'h' returns '5' (5 matches with the h)
find_match 4*ns 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*ha 4*5a 'h'
Just '5'
findMatch 4*ns 4dhnn 'k'
Nothing
-- Don
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http://www.nabble.com/Java-or-C-to-Haskell-tf2303820.html#a6404324
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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*ha 4*5a 'h' returns '5' (5 matches with the h) find_match 4*ns 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
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
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
... 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*ha 4*5a 'h' returns '5' (5 matches with the h) find_match 4*ns 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
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*ha 4*5a 'h' returns '5' (5 matches with the h) find_match 4*ns 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
