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This is an interpreter for SPL (Stupid Programming Language). It builds
jjtree's for a given SPL program and interprets it. It shows how you can
implement simple loop and conditional constructs.

Note how easy it is to annotate a grammar file to build useful tree nodes
and then extend these nodes for purposes of interpreting, etc.

This example will be improved as JJTree evolves.

To run it :

     jjtree SPL.jjt
     javacc SPL.jj
     javac *.java
     java SPL fact.spl
     java SPL sqrt.spl
     java SPL odd.spl
