[Haskell-cafe] Re: A suggestion for the next high profile Haskell project [Was: Re: What is a hacker?]

Brandon S. Allbery KF8NH allbery at ece.cmu.edu
Tue Dec 19 16:09:42 EST 2006

On Dec 19, 2006, at 16:03 , minh thu wrote:

> 2006/12/19, Neil Mitchell <ndmitchell at gmail.com>:
>> not_term = non_term
>> f x = 12
>> Now evaluating:
>> main = f non_term
>> In a lazy language the value is always 12, in a strict language its
>> always _|_. Now let's inline f:
>> main = 12
>> In a lazy language the value is still 12, in a strict language the
>> value has changed.
> Sorry, I don't see how it has changed.
> Isn't it still _|_ ?  i.e.

No, because inlining f results in the inlined value being 12, where  
it used to be _|_.  Depending on the optimizer, it may well drop the  
call to non_term entirely because it's not being used (thus changing  
program semantics), or it may continue to call it (final result will  
remain _|_ because the inlined value is never reached).

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

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