Template Haskell

Template Haskell is an experimental language extension to the programming language Haskell implemented in the Glasgow Haskell Compiler (version 6 and later).

In early incarnations it was also known as Template Meta-Haskell.

It allows compile-time metaprogramming and generative programming by means of manipulating abstract syntax trees and 'splicing' results back into a program. The abstract syntax is represented using ordinary Haskell data types and the manipulations are performed using ordinary Haskell functions.

'Quasi-quote' brackets [| and |] are used to get the abstract syntax tree for the enclosed expression and 'splice' brackets $( and ) are used to convert from abstract syntax tree into code.

Example

A common idiom is to quasi-quote an expression, perform some transformation on the expression and splice the result back into the program. It could be written as:

foo = $( transform [| bar |] )

External links

* [http://www.haskell.org/haskellwiki/Template_Haskell Template Haskell Wiki Page]
* [http://www.haskell.org/th/ The Template Haskell Home Page (rather old at this moment)]