Hello all, the and function, and :: [Bool] -> Bool is defined in two different ways in the latest Prelude. I would expect it to be
and = foldr (&&) True
However, there is a further recursive definition, and it is the one used! See http://haskell.org/ghc/docs/6.12.2/html/libraries/base-4.2.0.1/src/GHC-List....
#ifdef USE_REPORT_PRELUDE and = foldr (&&) True or = foldr (||) False #else and [] = True and (x:xs) = x && and xs or [] = False or (x:xs) = x || or xs
{-# RULES
"and/build" forall (g::forall b.(Bool->b->b)->b->b) .
and (build g) = g (&&) True
"or/build" forall (g::forall b.(Bool->b->b)->b->b) .
or (build g) = g (||) False
#-} #endif
Is there any reason for that besides some clever optimizations? I am particularly interested in the behavior of and for infinite lists and these two versions are equivalent in this aspect. Greetings, Oleg