[Haskell-cafe] Packed String parameters

Scherrer, Chad Chad.Scherrer at pnl.gov
Wed Jan 18 17:09:38 EST 2006

To read a file using a packed string, I need to use this function,

hGetPS :: Handle -> Int -> IO PackedString

What's the Int? Do you have to specify the length in advance? I don't
know how packed strings are implemented, and I'm having trouble finding
much documentation.

I'm trying to speed up this horribly slow thing:

dot :: [Double] -> [Double] -> Double
dot x y = sum $ zipWith (*) x y

main = getContents >>= sequence_ . map (print . dot weights . map read .
words) . lines

The idea is to take a dot product of each line of a file with a fixed
vector of weights, and send the result to stdout. I thought
PackedString's might help, but I'm not sure what to do with that
parameter. The input file is over 1 million lines long. Any ideas?


Chad Scherrer
Computational Mathematics Group
Pacific Northwest National Laboratory

"Time flies like an arrow; fruit flies like a banana." -- Groucho Marx

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