[Haskell-cafe] Comments from OCaml Hacker Brian Hurt

[Derek Elkins]

On Fri, 2009-01-16 at 15:21 -0800, Jonathan Cast wrote:
> On Fri, 2009-01-16 at 18:14 -0500, Anton van Straaten wrote:
> > Niklas Broberg wrote:
> > >> I still think existential quantification is a step too far though. :-P
> > > 
> > > Seriously, existential quantification is a REALLY simple concept, that
> > > you would learn week two (or maybe three) in any introductory course
> > > on logic. In fact, I would argue that far more people probably know
> > > what existential quantification is than that know what a monoid is.
> > > :-)
> > 
> > Andrew's core objection here seems reasonable to me.  It was this:
> > 
> >  > {-# LANGUAGE ExistentialQuantification #-} is an absurd name and
> >  > should be changed to something that, at a minimum, tells you it's
> >  > something to do with the type system.
> > 
> > But I suspect I part company from Andrew in thinking that something like 
> > ExistentiallyQuantifiedTypes would be a perfectly fine alternative.
> 
> +1

This focus on names is ridiculous.  I agree that good names are
beneficial, but they don't have to encode everything about the referent
into themselves.  Haskell is called "Haskell" not
"StaticallyTypedPurelyFunctionalProgrammingLanguage."  In this
particular case, it's absurd.  In this case the name is only of mnemonic
value, other than that it could be called FraggleRock.  Regardless of
the name you are going to have to look up what it refers to (in the
user's guide), or, having already done that earlier, just know what it
means.

> (Although shouldn't it really be ExistentiallyQuantifiedConstructorTypes
> or something?  If GHC ever actually adds first-class existentials, what
> is Cabal going to call *that* then?)

FreeExistentials.  FirstClassExistentials would also be reasonable.
Though renaming the current LANGUAGE tag to
LocalExistentialQuantification would be better.