This paper gives a static semantics for Haskell 98, a non-strict purely functional programming
language. The semantics formally specifies nearly all the details of the Haskell 98 type system,
including the resolution of overloading, kind inference (including defaulting) and polymorphic
recursion, the only major omission being a proper treatment of ambiguous overloading and
its resolution. Overloading is translated into explicit dictionary passing, as in all current
implementations of Haskell. The target language of this translation is a variant of the
Girard–Reynolds polymorphic lambda calculus featuring higher order polymorphism and
explicit type abstraction and application in the term language. Translated programs can thus
still be type checked, although the implicit version of this system is impredicative. A surprising
result of this formalization effort is that the monomorphism restriction, when rendered in a
system of inference rules, compromises the principal type property.