(Redirected from haskell to haskell-cafe.) Well, I tried to fix the problems you mention. Results attached. I have managed to do without de Brujin notation. The evaluator is (modulo bugs!) normal order. One can easily do an applicative order evaluator as well. Evaluating to WHNF is probably easy too (this is what the previous version supposed to do). I'll try to come up with a regression test suite for this stuff as my (copious :) free time permits, but on the surface it looks ok. --- oleg@pobox.com wrote:
anatoli <anatoli at yahoo> wrote:
This is all, of course, of purely academical interest. The notation is extremely inconvenient to do any real work. I'd rather prefer a real, language-supported lambda over types.
Or... wait a minute! You did find all those problems; does it mean you tried to *use* this stuff for something? Just curious.
I must start with a profuse apology, because what follows is perhaps of little relevance to the list. I also propose to re-direct the follow-ups to the Haskell Cafe.
I have examined your code and then tried a few examples, some of which from my code's regression tests.
I have implemented a compile-time lambda-calculator, in a different language. I should say, in a meta-language. The output of the evaluator is a term that can then be compiled and evaluated. The lambda-calculator acts as a partial evaluator. The calculator normalizes a term in a pure untyped lambda calculus. The result is compiled and evaluated in a call-by-value lambda-calculus with constants.
Haskell typechecker (augmented with multi-parameter classes with functional dependencies and let on loose) may do something similar.
BTW, the meta-language lambda-evaluator code (with the regression tests) can be found at http://pobox.com/~oleg/ftp/Computation/rewriting-rule-lambda.txt The calculator is implemented in CPS, in some sort of extended lambda calculus. Therefore, the code has three kinds of lambdas: of the source language, of the transformer meta-language, and of the target language. The first and the third lambdas are spelled the same and are the same.
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