Template Haskell
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Template Haskell is an experimental language extension to the programming language Haskell implemented in the compiler GHC (http://www.haskell.org/ghc/) (version 6 and later).
In early incarnations it was also known as Template Meta-Haskell.
It allows compile-time meta-programming and generative programming by means of manipulating abstract syntax trees and 'splicing' result 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 [| |] are used to get the abstract syntax tree for the enclosed expression and 'splice' brackets $( ) 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
- The Template Haskell Home Page (http://www.haskell.org/th/)