This example describes a grammar with terminal
and non terminal symbols (composition)
and production rules describing how the symbols
can be replaced.

Grammar.use:
several classes with generalization
and compositions compositions
for every class at least one simple invariant
with iterate and nested operations

Grammar.cmd:
a simple grammar is created
four terminal symbols +, -, 0 and 1
two non terminal symbols expr and operator
five production rules
<expr> -> <expr> <operator> <expr>
<expr> -> '0'
<expr> -> '1'
<operator> -> '+'
<operator> -> '-'

Grammar.fig:

Grammar.olt:
