What is it, specifically, that makes Haskell’s type system It has been engineered for the past decade to be both flexible — as a logic for property verification — and powerful. Haskell’s type system has been developed over the years to encourage a relatively flexible, expressive static checking discipline, with several groups of researchers identifying … Read more
Hindley-Milner is a type system discovered independently by Roger Hindley (who was looking at logic) and later by Robin Milner (who was looking at programming languages). The advantages of Hindley-Milner are It supports polymorphic functions; for example, a function that can give you the length of the list independent of the type of the elements, … Read more
The horizontal bar means that “[above] implies [below]”. If there are multiple expressions in [above], then consider them anded together; all of the [above] must be true in order to guarantee the [below]. : means has type ∈ means is in. (Likewise ∉ means “is not in”.) Γ is usually used to refer to an … Read more