[S-expressions] [1] (or sexps) are the minimal syntax of Lisp and Scheme. Here are some tools for parsing and manipulating them in SML. The code has been tested on SML/NJ v110.69. To generate the lexer and parser you'll need SML/NJ's language processing tools [2]. On Ubuntu, the required packages are 'smlnj', 'libsmlnj-smlnj' and 'ml-lpt'. If you're missing the language processing tools, you can copy the pre-generated lexer and parser from the 'generated' directory: $ cp generated/* . To build: $ smlnj Standard ML of New Jersey v110.69 [built: Mon Jun 8 14:15:08 2009] - CM.make "util.cm"; See the comments in src/syntaxrule.sml for more information on the utilities. [1] http://en.wikipedia.org/wiki/S-expression [2] http://smlnj-gforge.cs.uchicago.edu/projects/ml-lpt/