HList

Heterogeneous lists.

HList provides many operations to create and manipulate heterogenous lists (HLists) whose length and element types are known at compile-time. HLists are used to implement

• records

• variants

• type-indexed products (TIP)

• type-indexed co-products (TIC)

• keyword arguments

User code should import Data.HList or Data.HList.CommonMain for a slightly more limited scope

The original design is described in http://okmij.org/ftp/Haskell/HList-ext.pdf, though since that paper came out, the -XTypeFamiles extension has been used to replace TypeCast with ~.