On Mon, 21 Jan 2013, miphis@meta.ua wrote:

The program looks like this:

--*********************** factorial :: Int->Int factorial n = product [1..n]

main = do print $ factorial 50 --***********************

And that yields "0" (no errors). Is it a bug or feature? :)

This question is certainly better posted to haskell-cafe. The answer is: Int has limited bitsize (32 ord 64 bit depending on your machine), thus it computes factorial modulo 2^32 or 2^64. You can get the correct result by replacing Int by Integer.