I'm just copying code from this web page: http://en.wikibooks.org/wiki/Haskell/Understanding_monads
================
Using their initial seed I get this:
*Main> rollDie 362354 ~>> (rollDie ~>> rollDie)
<interactive>:1:0:
Couldn't match expected type `t -> (t1, t2)'
against inferred type `(Int, Seed)'
In the first argument of `(~>>)', namely `rollDie 362354'
In the expression: rollDie 362354 ~>> (rollDie ~>> rollDie)
In the definition of `it':
it = rollDie 362354 ~>> (rollDie ~>> rollDie)
*Main>
===================
Passing their initial seed through successive calls to rollDie:
*Main> rollDie 362354
Loading package old-locale-1.0.0.1 ... linking ... done.
Loading package old-time-1.0.0.1 ... linking ... done.
Loading package random-1.0.0.1 ... linking ... done.
(3,1795116384)
*Main> rollDie 1795116384
(1,523309185)
*Main> rollDie 523309185
(4,1311937830) <== ISN'T THIS SUPPOSED TO BE THE RESULT?
*Main>
Michael
--- On Wed, 4/22/09, Achim Schneider
OK, I changed the operator from (>>) to (~>>). When I try to use it I get this:
[michael@localhost ~]$ ghci rand GHCi, version 6.10.1: http://www.haskell.org/ghc/__ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Main________________________ ( rand.hs, interpreted ) Ok, modules loaded: Main. *Main> rollDie ~>> (rollDie ~>> rollDie)
<interactive>:1:0: ______ No instance for (Show (Seed -> (Int, Seed))) __________ arising from a use of `print' at <interactive>:1:0-32 ______ Possible fix: __________ add an instance declaration for (Show (Seed -> (Int, Seed))) ______ In a stmt of a 'do' expression: print it
Well, you obviously need an initial seed: rollDie 0xdeadbeef ~>> (rollDie ~>> rollDie) -- (c) this sig last receiving data processing entity. Inspect headers for copyright history. All rights reserved. Copying, hiring, renting, performance and/or quoting of this signature prohibited. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe