[Haskell-cafe] A suggestion for the next high profile Haskell project

Stefan O'Rear stefanor at cox.net
Tue Dec 19 16:16:18 EST 2006

On Tue, Dec 19, 2006 at 08:57:33PM +0000, Neil Mitchell wrote:
> >I don't know if any actual language does this,
> What, that is strict and would like to inline things for performance?
> There is a reason they can't do this.

I had intended for that to apply to my proposal - I know real strict
languages have inlining issues.
> >but your inlining problem can
> >be solved by letting _|_ = arbitrary behaivor.
> So would you allow folding? (inlining = unfolding) i.e. replacing
> defined behaviour with _|_?
> And how many equational reasoning steps do you have to go, before your
> program is totally different?

In my idea, the rule:

forall a. _|_ -> a

only works forward - so you can turn a program that fails into a program
that fails silently, but a working program must stay a working program.

This was intended to make optimizing compilation easier, human equational
reasoners would not be the intended beneficiaries.  This proposal effectively
allows a compiler to assume that a program will terminate successfully; a
strictly weaker set of deduction rules would correspond to leaving evaluation
order unspecified. 

I apologize for the unclearness.


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