Hi, I came upon this when playing with foldr and filter. Compare the two definitions:
testr n = foldr (\x y -> x && y) True [t | (_, t) <- zip [1 .. n] [True, True ..]] testr' n = foldr (\x y -> y && x) True [t | (_, t) <- zip [1 .. n] [True, True ..]] I tried these functions on ghci (The Glorious Glasgow Haskell Compilation System, version 7.0.3), and get the following results (with :set +s): testr 1000000 => True (0.01 secs, 7920832 bytes) testr' 1000000 => True (8.72 secs, 446585344 bytes) This bizarre (at least to me) behavior also applies to ||. Should I mind the orderings of the parameters (especially the accumulator) in the function passed to foldr? Thak you for reading. Sincerely yours, Frodo Chao
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