I have developped and implemented one such language as part of my thesis
research, called the "Elements, Events & Transitions" language. The
implementation is in C++ and contains the langauge representation, a
parser, and an interpreter.
Documentation including examples in postscript are under "The Elements,
Events & Transitions Model" at the bottom of my home page:
http://www.cc.gatech.edu/gvu/people/Phd/Martin.Frank.html
So, take a look if you are interested - reusing or adapting my
"transitions" for your "expressions" may save a lot of effort.
Yours, cheers, Martin
-- Martin R. Frank email: [email protected] Graphics, Visualization & Usability Center phone: (404) 853-9382 Georgia Institute of Technology fax: (404) 853-0673 Atlanta, GA 30332-0280