s-cargot

S-Cargot is a library for parsing and emitting S-expressions, designed to be flexible, customizable, and extensible. Different uses of S-expressions often understand subtly different variations on what an S-expression is. The goal of S-Cargot is to create as many reusable components that can be repurposed to nearly any S-expression variant.

Additionally, S-Cargot uses these to include out-of-the-box parsing and processing for several existing variations on S-expressions, including Common Lisp (in progresss), Scheme (in progress), the Rivest internet-draft (in progress), and Clojure (in progress).

The central way of interacting with the S-Cargot library is by creating and modifying a spec, which is a value that represents a given family of S-expressions. A spec, which is of type SExprSpec, contains the information necessary to implement reader macros, arbitrary kinds of comments, and various processing steps. A SExprSpec has two type parameters:

                      +------ the type that represents a SExpr atom
                      |
                      |    +- the Haskell representation of the SExpr value
                      |    |
someSpec :: SExprSpec atom carrier

There are three built-in representations of S-expression lists: two of them are isomorphic, as one or the other might be better for processing S-expression data, and the third represents only a subset of possible S-expressions.

-- cons-based representation
data SExpr atom = SAtom atom | SCons (SExpr atom) (SExpr atom) | SNil

-- list-based representation
data RichSExpr atom
  = RSList [RichSExpr atom]