Patterns of generic programming

Jeremy Gibbons describes seven patterns of generic programming, where each pattern is viewed as a different kind of parameterization. For more information, refer to his article, Datatype-Generic Programming, which is available at http://www.cs.ox.ac.uk/jeremy.gibbons/publications/dgp.pdf.

Patterns 1 and 2 – functions

Functions parameterized by values are more general than functions with hardcoded values. This is the most simple kind of generic programming.

Functions parameterized by functions (higher order functions) represent a more powerful form of genericity.

Pattern 3 – polymorphic types and functions

Types parameterized by other types are as follows:

  Tree a = Leaf a | Node a (Tree a)
  – is more generic than
  TreeI  = Leaf Int | Node Int TreeI

Functions parameterized by polymorphic types are as follows:

  f :: Tree a → a
  – is more generic than
  g :: String → String

Pattern 4 – type-class polymorphism

In the...