# Correctly parses the following string: 2+5*3*(2*8+6)
# Note that spaces between numbers/operators are currently not supported by this
# example grammar.
Expr     <- Factor AddExpr*
AddExpr  <- ( '+' / '-' ) Factor
Factor   <- Primary MulExpr*
MulExpr  <- ( '*' / '/' ) Primary
Primary  <- '(' Expr ')'
          / Number
          / Variable
          / '-' Primary

Number   <- [0-9]+
Variable <- identifier

lowerCase  <- [a-z]
upperCase  <- [A-Z]
digit      <- [0-9]
underscore <- '_'
identifier <- (lowerCase / upperCase / underscore) (lowerCase / upperCase / underscore / digit)*