[Haskell-cafe] A suggestion for the next high profile Haskell project

[Stefan O'Rear]

On Tue, Dec 19, 2006 at 08:42:06PM +0000, Neil Mitchell wrote:
> Lack of mutable state, referentially transparent and laziness all help
> with equational reasoning. Inlining is much easier in a lazy language
> - and inlining is really handy for equational reasoning.
> 
> Imagine:
> 
> 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.

I don't know if any actual language does this, but your inlining problem can
be solved by letting _|_ = arbitrary behaivor.  (Of course, I would want a 
debugging option that gives errors on all arbitrary behaivior.)