Guile manual has nice details about data representation: http://www.gnu.org/software/guile/manual/html_node/Data-Representation.html http://www.gnu.org/softwar

Guile manual has nice details about data representation: http://www.gnu.org/software/guile/manual/html_node/Data-Representation.html http://www.gnu.org/software/guile/manual/html_node/Data-Repr... Tagging: http://www.gnu.org/software/guile/manual/html_node/Faster-Integers.html http://www.gnu.org/software/guile/manual/html_node/Faster-In... Another interesting technique is NaN-tagging (used in LuaJIT): http://wingolog.org/archives/2011/05/18/value-representation-in-javascript-implementations http://wingolog.org/archives/2011/05/18/value-representation...