Re: dynamic vs. static typing

[Joe Marshall <address@hidden>]

Matt Hellige <matt@immute.net> writes:

> The reason I don't think we're seeing any great examples of TRULY
> heterogeneous lists of completely abstract, unconstrained values is
> that, as has been amply pointed out, such a thing is literally,
> exactly and provably no more useful than (and, in fact, equivalent to)
> a natural number. I don't know how to make that more clear.

The reason there are no `TRULY heterogeneous lists' is because it is
always possible to create a discriminated union type that covers all
elements.

It is especially pointless if you fold all operations on objects
into the object interface itself.

But if you take the view that certain operations (like intensional
equivalence or intensional identity) are independent of the objects,
then the notion of heterogeneous lists becomes much more interesting.
Permutation, for example, becomes possible.