15 Oct
2008
15 Oct
'08
1:09 p.m.
On Wed, Oct 15, 2008 at 6:05 AM,
Regarding existentials, the web page http://okmij.org/ftp/Computation/Existentials.html
demonstrates how to systematically eliminate existentials. In fact, the object encoding via existentials can be easily transformed into the encoding that uses only simple, first-order types. The web page begs a question if there is ever any real need for existentials.
We might justify existential types on performance grounds. Stream
fusion, for example, uses existentials to replace recursive types and
functions with non-recursive types and functions, which are simpler to
optimize.
--
Dave Menendez