[Haskell-cafe] Re: Currying and Partial Evaluation
derek.a.elkins at gmail.com
Tue Jan 8 21:01:14 EST 2008
On Wed, 2008-01-09 at 03:37 +0100, Achim Schneider wrote:
> Derek Elkins <derek.a.elkins at gmail.com> wrote:
> > On Wed, 2008-01-09 at 00:51 +0100, Achim Schneider wrote:
> > > Fernando Rodriguez <frr149 at easyjob.net> wrote:
> > >
> > > >
> > > > Hi,
> > > >
> > > > Is currying in Haskell the same thing as Partial Evaluation
> > > > (http://en.wikipedia.org/wiki/Partial_evaluation)? Am I getting
> > > > partial evaluation for free just by using Haskell?
> > > >
> > > No, currying is this:
> > No, it is not. This is partial application. See the wiki page Neil
> > referenced.
> Which works because of the functions being curried...
and therefore partial application can't be currying. Currying is the
operation of turning (a,b) -> c into a -> b -> c. Nothing more.
> of course, the
> usage is to "partly" apply a function, which is not possible, as all
> Haskell functions are, by default, curried, and thus only have one
> parameter, which can either be applied or not.
Indeed. Partial application is a fuzzy term. I give a potential
objective definition here:
> Partial evaluation, OTOH, goes into the direction of laziness vs.
> eagerness: Iff the compiler sees that a thunk is only dependent on data
> known at compile-time, it may choose to evaluate this thunk already at
> compile-time, if you're lucky and the compiler isn't lazy,
Partial evaluation has little to do with lazy v. eager evaluation.
> main = putStrLn $ show $ 1 + 2
> might end up being
> main = putStrLn "3"
> in the object file.
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