Re: [Haskell-cafe] Re: Re-order type

djinn[1] can derive some glue functions for you. you tell it something like

glue :: (x -> y -> z -> (b,(c,a)) -> (c -> a -> d) -> x -> y -> z -> d and it tells you something like glue f g x y z = let (b,(c,a)) = f x y z in g c a I changed the type of f slightly to avoid the trivial answer glue _ g a _ c = g c a

[1] http://hackage.haskell.org/package/djinn 2010/10/9 André Batista Martins :

Might have not been clear, but i will try illustrate .

f:: a-> b -> c -> (b,(c,a))

f1 ::  c -> a -> d

input type:                                A   B   C                                  ----------                                |    f      |                                | _____ |

output                       (B,(C,A))

                                 C    A                                  ----------                                |    f1    |                                | _____ |

output                         D

If i want compose   f  and f1, i need to do a correct input to f1 from the output of f. So i want one function to  convert the output of "f" to input off "f!". In this case,  we do      f1 fst (snd (t,(t1,t2)))  snd (snd (t,(t1,t2))) But i want do this automaticaly, for type of any two function. I search for the "glue".

I don't have any concern about what the function does, i only have interess on input and output types.

Cheers,  André

No dia 9 de Outubro de 2010 22:38, André Batista Martins escreveu:

...

Hello,  exists any algorithm  to determine how terms can be changed to safisty the type of one function?

example:

f:: a-> b -> c -> (b,c,a)

f1 ::  c -> a -> d

In my first function "f" i want assign  the output "c" and "a" for to input of function "f1". I searched for any solution, but i didn't find any anything.

One clue i have found is "minimal edit distance algorithm" for 2 strings. Perhaps if i convert de output type of "f" to one string, and de input of "f1" to another string and then use this algorithm , i will get one "dirty" solution...

I'm open to any sugestion.

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