[Haskell-cafe] Re: Why?

Tom Davie tom.davie at gmail.com
Thu Dec 10 10:55:20 EST 2009


Non-strictness is not necessary for purity, but it sure gives you some nice
properties... Take for example

const x y = x

It would be really nice for this function to have the property "always
results in x no matter what you give it as it's second argument".  But for a
language which is strict, all instances where computing y non-terminates
also non-terminate.

So yes, non-strictness is very much a property you want in a language.

Bob

On Thu, Dec 10, 2009 at 3:30 PM, John D. Earle <JohnDEarle at cox.net> wrote:

> My intuition says that laziness and purity are distinct whereas yours says
> that purity is a necessary condition. This is what needs to be reconciled.
>
> I believe that everyone is thinking that lazy evaluation and strict
> evaluation are similar activities whereas they are profoundly different.
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