const is:module

This module provides typed const pointers to foreign data. It is part of the Foreign Function Interface (FFI).
The constant functor.
Constants describing the DWARF format. Most of this simply mirrors /usr/include/dwarf.h.
Constant Folder
Compile-time settings
This module defines types and simple operations over constraints, as used in the type-checker and constraint solver.
Exports some POSIX constants and functions that are not exported in fptools by default.
ConstraintKinds made type classes into types of a new kind, Constraint.
Eq :: * -> Constraint
Ord :: * -> Constraint
Monad :: (* -> *) -> Constraint
The need for this extension was first publicized in the paper Scrap your boilerplate with class: extensible generic functions by Ralf Lämmel and Simon Peyton Jones in 2005, which shoehorned all the things they needed into a custom Sat typeclass. With ConstraintKinds we can put into code a lot of tools for manipulating these new types without such awkward workarounds.
Constructible types are those for which new is defined. Often these are GObjects, but it is possible to construct new (zero-initialized) structures and unions too.
Derive constructor-name-based prisms generically.
Parsing of constants in GIR files.
Constraints for indexed datatypes. This module contains code that helps to specify that all elements of an indexed structure must satisfy a particular constraint.