[Haskell-cafe] newbie question about list performance

John Lato jwlato at gmail.com
Mon Oct 29 01:02:47 EDT 2007

I've been following the list optimization thread with great interest,
as it pertains to something I'm working on at the moment.  I'm working
with moderate-sized files (tens to hundreds of MBs) that have some
ascii header data followed by a bunch of 32-bit ints.  I can read the
files into a lazy ByteString (and parse the header), but I'd like some
advice as to the best data type to convert the ints into.  Ideally,
I'd have some functions like this:
decode :: ByteString -> (FileFormat, [Int32])
encode :: FileFormat -> [Int32] -> ByteString

but I don't know if Int32 is actually the best choice.  It seems to me
that something like a lazy list of strict arrays (analogous to a lazy
bytestring) would be better.  Is there a library like this already?
Or is this a case of premature optimization, and I should just try the
list and see if it's good enough?  Any suggestions would be

Also, I'd like to let the maintainers and implementors know that I
really appreciate the work that's been done on optimizing Haskell.  I
haven't used Haskell much yet, but I've fallen in love with the
language and it's great to see that performance even for heavy I/O
tasks can be comparable to or exceed C.

Thank you,
John Lato

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