[Haskell-cafe] Re: A suggestion for the next high profile
Haskell project [Was: Re: What is a hacker?]
ndmitchell at gmail.com
Tue Dec 19 15:42:06 EST 2006
Hi minh thu,
> Lazy semantics -> equational reasoning ?
> I thought that : lack of mutable state -> equational reasoning.
> For instance, I think to data flow variable in Oz (whcih I really
> don't know much / never used) : if a (Oz managed) thread attemps to
> read the value of an unbound (data flow) variable, it waits until
> another thread binds it. But the equational reasoning (referential
> transparency) remains (and the evaluation is eager by default).
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.
not_term = non_term
f x = 12
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.
Note how in a strict language inlining is not as safe as it once was...
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