[Haskell] Re: "exists" keyword and "existential" types

2004-02-16 Thread Ben Rudiak-Gould
On Mon, 16 Feb 2004, Ashley Yakeley wrote: > A value of "type" (exists t. Interface t => t) consists of two values, > one of type t, and one "dictionary" value. For that reason a data type > is used to represent this (and a newtype type cannot be). This is an implementation detail, though. It's

[Haskell] Re: "exists" keyword and "existential" types

2004-02-16 Thread Ashley Yakeley
In article <[EMAIL PROTECTED]>, Ben Rudiak-Gould <[EMAIL PROTECTED]> wrote: > And it would be nice to be able to pass around values of type > (exists t. Interface t => t), which behave just like OOP interface > pointers. A value of "type" (exists t. Interface t => t) consists of two values, one