[Haskell-cafe] I love purity, but it's killing me.

Tim Chevalier catamorphism at gmail.com
Fri Feb 8 10:02:57 EST 2008

On 2/8/08, Matthew Naylor <mfn-haskell-cafe at cs.york.ac.uk> wrote:
> it in for an efficient program.  However, to my knowledge, it is an
> unwritten rule of Haskell compilers that sharing *is* preserved, and
> that they do perform *graph* reduction.  Clean, a similar language to

I'm not sure that programmers ought to be relying on this rule. Sure,
all Haskell compilers I know of preserve sharing and do graph
reduction. But conventional wisdom is not the same thing as an
unwritten rule. Someday, someone might come along and write a Haskell
compiler that isn't based on graph reduction and doesn't preserve
sharing at the implementation level (while still preserving the
informal semantics of Haskell). A programmer who had written code that
failed to compile correctly under this hypothetical compiler would be
a very naughty Haskell programmer indeed.

> Haskell, indeed has a semantics based on graphs.  So I don't believe

Haskell doesn't have a semantics, graph-based or not... or at least
not a formal one, and if not a formal one, I don't know what you mean


Tim Chevalier * http://cs.pdx.edu/~tjc * Often in error, never in doubt
"There are no sexist decisions to be made. There are antisexist
decisions to be made. And they require tremendous energy and
self-scrutiny, as well as moral stamina..." -- Samuel R. Delany

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