. 
interval.sourceforge.net/scheme/giaeval
RUN GIAEVAL DEMO:
A Graphical User Interface to an interval arithmetic evaluator
which operates on general intervals
(i.e. finite unions of connected sets of reals as
described in the paper
Interval Arithmetic: from Principles to Implementation by Hickey, Qun, van Emden
This applet is implemented in entirely in JScheme
using the java.math.BigDecimal package to implement rounded arithmetic operations.
Source code
 opparse.scm  an operator precedence grammar parse generator in Scheme
 ereal.scm  an implementation of extended reals on top of java.math.BigDecimal
 gia.scm  an implementation of general interval arithmetic operations
 iaeval.scm  an interval arithmetic evaluator on syntax trees
 iaevaldemo.scm  a GUI for the general interval arithmetic evaluator
 iaevaldemo.html  the webpage containing the GUI
Related papers

"Interval Arithmetic: from Principles to Implementation"
(.ps.gz)
by Hickey, Qun, van Emden
Submitted to JACM

"Silk: A Playful Combination of Scheme and Java"
(.ps)
by Ken Anderson, Timothy J. Hickey, and Peter Norvig
in Proceeedings of
Scheme2000
