Re: [Haskell-cafe] Re-order type

[Lennart Augustsson]

You can use Djinn to generate the glue.  Note that in the example you
give there are many possible ways to make the glue just looking at the
types.
Changing the output types of f so they can't be confused with the
input types we get:

Djinn ? compose :: (c1 - a1 - d) - (a- b - c - (b1,c1,a1)) -
(a - b - c - d)
compose :: (c1 - a1 - d) - (a - b - c - (b1, c1, a1)) - a - b - c - d
compose a b c d e =
  case b c d e of
  (_, f, g) - a f g

  -- Lennart

2010/10/9 André Batista Martins andre...@netcabo.pt:
 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.

 ___
 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] Re-order type

[Edward Z. Yang]

Excerpts from André Batista Martins's message of Sat Oct 09 17:45:05 -0400 2010:
 Hello,
  exists any algorithm  to determine how terms can be changed to safisty the
 type of one function?

Your terminology is a little off: in particular, your example doesn't include
any terms (which are understood to be the things to the right of the =,
not the double-colon).

The term you are actually looking for is unification.  One way of looking
at this is that you have two types that are the same type, but due to their
structure they impose various constraints on each other. Solve all of the
constraints and you have a unified type (indeed, the best such type in
many type systems--the correct term is principal type), and if you can't
solve them then you have a type error.

Cheers,
Edward
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe