Spew Template for Simple Expressions

\* Spew template for simple arithmetic expressions

\* Digits
%DIGIT
0
1
2
3
4
5
6
7
8
9

\* Numbers, which are just strings of digits.
\* The numbers in parentheses add weight so they're chosen more often.
\* E.g., the first line is p(1/4) and the second is p(3/4)
%NUMBER
\DIGIT
(3)\DIGIT\NUMBER

\* Operators
%OP
+
-
*
/

\* Expressions.
%EXPR
(10)\NUMBER \OP \NUMBER
(\EXPR)
(10)(\EXPR \OP \EXPR)

\* This is where Spew starts, an EXPR followed by a newline
%MAIN
\EXPR\!