free-5.1.10: Monads for free
Free monads are useful for many tree-like structures and domain specific languages.
If
f
is a
Functor
then the free
Monad
on
f
is the type
of trees whose nodes are labeled with the constructors of
f
. The word
"free" is used in the sense of "unrestricted" rather than "zero-cost":
Free f
makes no constraining assumptions beyond those given by
f
and the
definition of
Monad
. As used here it is a standard term from the
mathematical theory of adjoint functors.
Cofree comonads are dual to free monads. They provide convenient ways to talk
about branching streams and rose-trees, and can be used to annotate syntax
trees. The cofree comonad can be seen as a stream parameterized by a
Functor
that controls its branching factor.
More information on free monads, including examples, can be found in the following blog posts: http://comonad.com/reader/2008/monads-for-free/ http://comonad.com/reader/2011/free-monads-for-less/
Modules
-
Control
- Alternative
- Applicative
- Comonad
- Monad