HMF is a conservative extension of Hindley-Milner type inference with first-class polymorphism. In contrast to other proposals, HML uses regular System F types and has a simple type inference algorithm that is just a small extension of the usual Damas-Milner algorithm W. Given the relative simplicity and expressive power, we feel that HMF can be an attractive type system in practice. There is a reference implementation of the type system available online together with a technical report containing proofs (Leijen 2007a,b). Categories and Subject Descriptors D.3.3 [Programming Languages]: Language Constructs and Features--Polymorphism General Terms Languages, Design, Theory Keywords Type Inference, First-class polymorphism