[Haskell-cafe] monadic performance

Tomasz Zielonka tomasz.zielonka at gmail.com
Sat Oct 28 05:42:49 EDT 2006

On Fri, Oct 27, 2006 at 06:28:58AM -0700, Chad Scherrer wrote:
> Should I expect a monadic version to take a performance hit? What if I
> use some SPECIALIZE pragmas or somesuch? Is it more efficient to write
> one from scratch, or do specific type annotations give me the same
> thing anyway?

I was recently making experiments with rewriting a decoder for some data
format in Haskell. At some point I had a hand-written State/Reader monad
using unboxed tuples and I tried rewriting it to monad transformers. I
was surprised that there was no difference in performance. This is a
change from monadic version to monadic version, but the speed was at
about 66% of the C++ version, so it seems monads didn't add much cost.
BTW, the state and enviroment were Ptrs.

Best regards

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