26 Jun
2010
26 Jun
'10
1:33 p.m.
On Jun 26, 2010, at 4:33 AM, Andrew Coppin wrote:
It's a bit like trying to learn Prolog from somebody who thinks that the difference between first-order and second-order logic is somehow "common knowledge".
A first order logic quantifies over values, and a second order logic quantifies over values and sets of values (i.e., types, predicates, etc). The latter lets you express things like "For every property P, P x". Notice that this expression "is equivalent" to Haskell's bottom type "a". Indeed, Haskell is a weak second-order language. Haskell's language of values, functions, and function application is a first- order language.