# The compdata package

Based on Wouter Swierstra's Functional Pearl *Data types a la carte*
(Journal of Functional Programming, 18(4):423-436, 2008,
http://dx.doi.org/10.1017/S0956796808006758),
this package provides a framework for defining recursive
data types in a compositional manner. The fundamental idea of
*compositional data types* (Workshop on Generic Programming, 83-94, 2011,
http://dx.doi.org/10.1145/2036918.2036930) is to separate the
signature of a data type
from the fixed point construction that produces its recursive
structure. By allowing to compose and decompose signatures,
compositional data types enable to combine data types in a flexible
way. The key point of Wouter Swierstra's original work is to define
functions on compositional data types in a compositional manner as
well by leveraging Haskell's type class machinery.

Building on that foundation, this library provides additional
extensions and (run-time) optimisations which make compositional data types
usable for practical implementations. In particular, it
provides an excellent framework for manipulating and analysing
abstract syntax trees in a type-safe manner. Thus, it is perfectly
suited for programming language implementations, especially, in an environment
consisting of a family of tightly interwoven *domain-specific languages*.

In concrete terms, this package provides the following features:

Compositional data types in the style of Wouter Swierstra's Functional Pearl

*Data types a la carte*.Modular definition of functions on compositional data types through catamorphisms and anamorphisms as well as more structured recursion schemes such as primitive recursion and co-recursion, and course-of-value iteration and co-iteration.

Support for monadic computations via monadic variants of all recursion schemes.

Support of a succinct programming style over compositional data types via generic programming combinators that allow various forms of generic transformations and generic queries.

Generalisation of compositional data types (terms) to compositional data types "with holes" (contexts). This allows flexible reuse of a wide variety of catamorphisms (called

*term homomorphisms*) as well as an efficient composition of them.Operations on signatures, for example, to add and remove annotations of abstract syntax trees. This includes combinators to propagate annotations fully automatically through certain term homomorphisms.

Optimisation of the implementation of recursion schemes. This includes

*short-cut fusion*style optimisation rules which yield a performance boost of up to factor six.Automatic derivation of instances of all relevant type classes for using compositional data types via

*Template Haskell*. This includes instances of`Prelude.Eq`,`Prelude.Ord`and`Prelude.Show`that are derived via instances for functorial variants of them. Additionally, also*smart constructors*, which allow to easily construct inhabitants of compositional data types, are automatically generated.*Mutually recursive data types*and*generalised algebraic data types (GADTs)*. All of the above is also lifted to families of mutually recursive data types and (more generally) GADTs. This extension resides in the module`Data.Comp.Multi`.Advanced recursion schemes derived from tree automata. These recursion schemes allow for a higher degree of modularity and make it possible to apply fusion. See

*Modular Tree Automata*(Mathematics of Program Construction, 263-299, 2012, http://dx.doi.org/10.1007/978-3-642-31113-0_14) and*Programming Macro Tree Transducers*(Workshop on Generic Programming, 61-72, 2013, http://dx.doi.org/10.1145/2502488.2502489).

Examples of using (generalised) compositional data types are bundled
with the package in the folder `examples`.

## Properties

Versions | 0.1, 0.2, 0.3, 0.4, 0.4.1, 0.5, 0.5.1, 0.5.2, 0.5.3, 0.6, 0.6.1, 0.6.1.1, 0.6.1.2, 0.6.1.3, 0.6.1.4, 0.7, 0.7.0.1, 0.7.0.2, 0.8, 0.8.0.1, 0.8.1.0, 0.8.1.1, 0.8.1.2, 0.8.1.3, 0.9, 0.10 |
---|---|

Change log | None available |

Dependencies | base (>=4.7 && <5), containers, deepseq, derive, mtl, QuickCheck (>=2), template-haskell, th-expand-syns, transformers, tree-view [details] |

License | BSD3 |

Author | Patrick Bahr, Tom Hvitved |

Maintainer | paba@diku.dk |

Category | Generics |

Bug tracker | https://bitbucket.org/paba/compdata/issues |

Source repository | head: hg clone https://bitbucket.org/paba/compdata |

Uploaded | Wed May 7 15:25:08 UTC 2014 by PatrickBahr |

Distributions | LTSHaskell:0.10, NixOS:0.10, Stackage:0.10 |

Downloads | 5270 total (56 in last 30 days) |

Votes | |

Status | Docs uploaded by user Build status unknown [no reports yet] |

## Modules

*Data*- Data.Comp
- Data.Comp.Algebra
- Data.Comp.Annotation
- Data.Comp.Arbitrary
- Data.Comp.Automata
- Data.Comp.Decompose
- Data.Comp.DeepSeq
- Data.Comp.Derive
- Data.Comp.Desugar
- Data.Comp.Equality
- Data.Comp.Generic
- Data.Comp.MacroAutomata
- Data.Comp.Matching
- Data.Comp.Multi
- Data.Comp.Multi.Algebra
- Data.Comp.Multi.Annotation
- Data.Comp.Multi.Derive
- Data.Comp.Multi.Desugar
- Data.Comp.Multi.Equality
- Data.Comp.Multi.Generic
- Data.Comp.Multi.HFoldable
- Data.Comp.Multi.HFunctor
- Data.Comp.Multi.HTraversable
- Data.Comp.Multi.Number
- Data.Comp.Multi.Ops
- Data.Comp.Multi.Ordering
- Data.Comp.Multi.Show
- Data.Comp.Multi.Sum
- Data.Comp.Multi.Term
- Data.Comp.Multi.Variables

- Data.Comp.Number
- Data.Comp.Ops
- Data.Comp.Ordering
- Data.Comp.Render
- Data.Comp.Show
- Data.Comp.Sum
- Data.Comp.Term
- Data.Comp.TermRewriting
- Data.Comp.Thunk
- Data.Comp.Unification
- Data.Comp.Variables

- Data.Comp

[Index]

## Downloads

- compdata-0.8.0.1.tar.gz [browse] (Cabal source package)
- Package description (included in the package)

#### Maintainers' corner

For package maintainers and hackage trustees