Comparing revisions for page haskellComposition

  == Headline ==

[[Data composition]] in [[Language:Haskell|]] with [[algebraic data type]]s

== Characteristics ==

The [[data model]] leverages [[data composition]] for companies with departmental nesting. Thus, an [[algebraic data type]] is used for departments so that recursive nesting can be expressed. The algebraic data type only needs a single [[data constructor]]. Thus, [[data variation]] is not exercised, but see [[Contribution:haskellVariation]] for an alternative with data variation.

== Illustration ==

The data model leverages an [[algebraic data type]] for departments; in this manner recursion is enabled:

    

A sample company looks like this:

    

[[Feature:Total]] is implemented as follows:

    

The following salary total is computed for the sample company:


399747.0


== Relationships ==

* See [[Contribution:haskellVariation]] for a contribution with a similar data model such that [[data variation]] is exercised in addition to [[data composition]].
* See [[Contribution:haskellEngineer]] for a contribution with a simple data model without support for departmental nesting. No algebraic data types are leveraged.
* See [[Contribution:haskellData]] for a contribution with a simple data model without support for departmental nesting. Algebraic data types are leveraged systematically for all types to distinguish the types nominally.

== Architecture ==

There are these modules:

* : a data model for [[Feature:Hierarchical company]]
* : a sample company
* : the implementation of [[Feature:Total]]
* : the implementation of [[Feature:Cut]]
* : Tests

The types of  implement [[Feature:Closed serialization]] through Haskell's read/show.

== Usage ==

See https://github.com/101companies/101haskell/blob/master/README.md.

== Metadata ==

* [[uses::Language:Haskell]]
* [[uses::Language:Haskell 98]]
* [[uses::Technology:GHC]]
* [[uses::Technology:Cabal]]
* [[implements::Feature:Hierarchical company]]
* [[implements::Feature:Total]]
* [[implements::Feature:Cut]]
* [[implements::Feature:Closed serialization]]
* [[developedBy::Contributor:rlaemmel]]
* [[memberOf::Theme:Haskell data]]
* [[memberOf::Theme:Haskell introduction]]
* [[varies::Contribution:haskellVariation]]
* [[basedOn::Contribution:haskellEngineer]]