This library contains functionality for parsing and pretty-printing S-expressions. In addition to that it contains an extremely useful preprocessing module for Camlp4, which can be used to automatically generate code from type definitions for efficiently converting OCaml-values to S-expressions and vice versa. In combination with the parsing and pretty-printing functionality this frees the user from having to write his own I/O-routines for data structures he defines. Possible errors during automatic conversions from S-expressions to OCaml-values are reported in a very human-readable way. Another module in the library allows you to extract and replace sub-expressions in S-expressions. WWW: http://janestreet.github.io/