Re: [Haskell-cafe] hash of a lazy bytestring?

On Sun, 13 May 2007, David Roundy wrote:

I was just contemplating hashes, and it occurred to me that it would be nice to be able to compute the hash of a lazily constructed bytestring and lazily consume its output without requiring the whole string to ever be in memory. Or in general, it'd be nice to be able to perform two simultaneous consumptions of a lazy list without requiring that the entire list be stored. Another example would be computing the length of an ordinary list:

do l <- readFile "foo" let len = length l writeFile "bar" l putStrLn $ "Length is " ++ show l

An elegant implementation of 'wc' is another example.