Re: strictness of unused arguments

Thanks for the answer. Sorry, I can not follow all of your thoughts because my knowledge of strictness analysis and GHC optimizations are very basic. :( I looked into GHC code once several years ago. BTW there are a lot of papers about strictness analysis, but I do not know which is relevant for GHC. Can you suggest something? On 11.03.10 23:33, Max Bolingbroke wrote:

On 11 March 2010 12:50, Roman Beslik wrote:

...

I also can force the analyzer to think that "x1" and "x0" are strict by eta-expanding "f3":

There seem to be two issues here.

1) GHC only figures out and records strictness information on lambdas that are syntactically together. I'm not sure how hard it would be to change this, but probably not totally straightforward

So GHC records strictness information for lambda-abstractions, not for function types? Eta-expansion changes strictness because it adds lambda-abstractions.

2) GHC does not seem to be eta-expanding as much as it could get away with. Generally eta expansion has the following effects

I think it is better to go without eta-expansion. Eta-expansion (if not optimized when compiled) do absolutely useless job. I discovered its effect by an accident.

Out of curiosity, did you spot this in a real program?

It may be a real program. :) From the higher-level point of view: A list of Int-s is replaced by seed+coalgebra and a coalgebra is an automaton. The program generates lists and folds them, or in other words the program is a sequence of automata which feeds each other. The special feature is that states of all automata lay in stack, the program *does not allocate in the heap*. Of course, if it uses boxed Int-s, the very goal is missed. :( However, for now I can compose automata only by hand :( , I did not figured out a (.) function. -- Best regards, Roman Beslik.