We have developed a library for constructing composable, monadic interpreters in Haskell. The InterpreterLib library provides a collection of functions and type classes that implement semantic algebras in the style of Hutton and Duponcheel. InterpreterLib structures interpreters around a Functor and Algebra written for each AST construct. AST elements are defined non-recursively and composed using a Sum type. The actual language is formed by taking the least fixed point of the language Sum. To interpret and AST element, a general catamorphism is applied using Haskell's typeclass system to select an appropriate algebra for interpreting each element.
Use the Haddock documentation for InterpreterLib for reference.
The AST Builder executable provides a compiler for a small language for specifying regular languages (not yet released). The compiler output consists of Haskell modules of boilerplate for functors and their algebras.
The Algebra Compiler (algc) defines a language and compiler for defining boilerplate for semantic algebras. algc is not required to use InterpreterLib, but is highly useful for defining semantic algebras over InterpreterLib structures.
Also included is TermLib, a collection of pre-defined standard AST elements that represent many common language constructs (not yet released). If an AST construct is not available, the AST Builder astbuilder can be used to automatically generate necessary data structures and boilerplate from a simple interface specification.
