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From: Sebastian Hanowski <sebastian.hanowski_at_web.de>

Date: Thu, 20 Mar 2008 18:46:26 +0100

* Am 19.03.08 schrieb Sergio Antoy:

*> Sebastian,
*

*>
*

*> Interesting snippets! Nothing specific to parallelism, right?
*

No, you're right even if had sent the program that I intended to:

pmap :: (a -> b) -> [a] -> [b]

pmap _ [] = []

pmap f (x:xs) | y =:<= f x & ys =:<= pmap f xs = y : ys

where

y,ys free

fix :: ((a -> b) -> (a -> b)) -> (a -> b)

fix f a = foldr1 (?) [k a | k <- chain]

where

chain = failed : pmap f chain

I need more time to consider your programs and it's specifications

respectively. Until now I only have these two following remarks.

Best regards,

Sebastian

First, I'd argue that your function /f/

data Token = Stop | Loop | Fail

-- f :: Token -> Token

-- f Stop = Stop

-- f Loop = f Loop

does the same as this one

f :: Token -> Maybe ()

f Stop = Just ()

f Loop = Just bot where bot = bot

f Fail = Nothing

because /pattern match failure/ is a finite failure and hence

observable.

And secondly I'd like to note that your function /g/

-- g :: (Token,Token) -> (Token,Token)

-- g (a,b) = (f a, f b)

could be factored with the help of a function /pair/ which does for

tuples what /map/ does for lists.

g :: (Token,Token) -> (Maybe (),Maybe ())

g = pair f f

And which could be implemented following the idea for the parallel

/map/.

pair :: (a -> c) -> (b -> d) -> (a,b) -> (c,d)

pair h k (a,b) | a' =:<= (h a) & b' =:<= (k b) = (a',b')

where a',b' free

But this still does not suffice to meet your specifications.

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Received on So Mär 23 2008 - 19:01:28 CET

Date: Thu, 20 Mar 2008 18:46:26 +0100

* Am 19.03.08 schrieb Sergio Antoy:

No, you're right even if had sent the program that I intended to:

pmap :: (a -> b) -> [a] -> [b]

pmap _ [] = []

pmap f (x:xs) | y =:<= f x & ys =:<= pmap f xs = y : ys

where

y,ys free

fix :: ((a -> b) -> (a -> b)) -> (a -> b)

fix f a = foldr1 (?) [k a | k <- chain]

where

chain = failed : pmap f chain

I need more time to consider your programs and it's specifications

respectively. Until now I only have these two following remarks.

Best regards,

Sebastian

First, I'd argue that your function /f/

data Token = Stop | Loop | Fail

-- f :: Token -> Token

-- f Stop = Stop

-- f Loop = f Loop

does the same as this one

f :: Token -> Maybe ()

f Stop = Just ()

f Loop = Just bot where bot = bot

f Fail = Nothing

because /pattern match failure/ is a finite failure and hence

observable.

And secondly I'd like to note that your function /g/

-- g :: (Token,Token) -> (Token,Token)

-- g (a,b) = (f a, f b)

could be factored with the help of a function /pair/ which does for

tuples what /map/ does for lists.

g :: (Token,Token) -> (Maybe (),Maybe ())

g = pair f f

And which could be implemented following the idea for the parallel

/map/.

pair :: (a -> c) -> (b -> d) -> (a,b) -> (c,d)

pair h k (a,b) | a' =:<= (h a) & b' =:<= (k b) = (a',b')

where a',b' free

But this still does not suffice to meet your specifications.

_______________________________________________

curry mailing list

curry_at_lists.RWTH-Aachen.DE

http://MailMan.RWTH-Aachen.DE/mailman/listinfo/curry

Received on So Mär 23 2008 - 19:01:28 CET

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