[Haskell-cafe] Re: [Haskell] Fixpoint combinator without recursion

Jan-Willem Maessen jmaessen at alum.mit.edu
Wed Apr 4 21:47:13 EDT 2007

On Apr 4, 2007, at 5:01 PM, Edsko de Vries wrote:

>> Yeah, it's rather cool. IIRC, this style of encoding of recursion
>> operators is attributed to Morris.
> Do you have a reference?
>> Before the advent of equality coercions, GHC typically had problems
>> generating code for these kinds of definitions. Did you test this
>> with a release version? If so, how did you get around the code-
>> generation problem? Is it the NOINLINE pragma that does the trick?
> Yep. Without the NOINLINE pragma, ghc tries to inline the  
> definition of
> fac, expanding it ad infinitum (this is a known bug in ghc and  
> mentioned
> in the ghc manual). Hugs doesn't have a problem though.

I keep waiting for someone to use this fact to cook up a poor man's  
partial evaluation---use fix for static recursion, and ordinary  
recursive definitions for dynamic recursion.  I fiddled with this a  
bit in the pH days (it had the same bug, for much the same reason).

-Jan-Willem Maessen

> Edsko
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