[Haskell-beginners] fix

[Brandon S. Allbery KF8NH]

On 2008 Oct 15, at 18:51, Matthew J. Williams wrote:
> 	fix (\rec n -> if n == 0 then 1 else n * rec (n-1)) 5
> 	120
>
> 	My interpretation:
> 	fix (\rec n -> if n == 0 then 1 else n * rec (n-1)) 5
> 	((\rec n -> if n == 0 then 1 else n * rec (n-1)) (fix (\rec n -> if  
> n == 0 then 1 else n * rec (n-1)) )) 5
> 	. . .
>
> 	Yet, it does not quite explain how 'fix' does not result in  
> infinite recursion.


Remember, Haskell is non-strict.  When the computation reaches 0, the  
"then" branch of the conditional is evaluated and the "else" is  
unneeded and therefore ignored, so its re-invocation isn't seen.

-- 
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery at kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university    KF8NH