peg 0.2.2

A parser generator built on the Parsing Expression Grammar (PEG) formalism. 
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#![feature(plugin, collections, str_char)]
#![plugin(peg_syntax_ext)]
use arithmetic::expression;

peg! arithmetic(r#"
#[pub]
expression -> i64
	= sum

sum -> i64
	= l:product "+" r:product { l+r }
	/ product

product -> i64
	= l:atom "*" r:atom { l*r }
	/ atom

atom -> i64
	= number
	/ "(" v:sum ")" { v }

number -> i64
	= [0-9]+ { match_str.parse().unwrap() }
"#);

#[test]
fn main() {
	assert_eq!(expression("1+1"), Ok(2));
	assert_eq!(expression("5*5"), Ok(25));
	assert_eq!(expression("222+3333"), Ok(3555));
	assert_eq!(expression("2+3*4"), Ok(14));
	assert_eq!(expression("(2+2)*3"), Ok(12));
	assert!(expression("(22+)+1").is_err());
	assert!(expression("1++1").is_err());
	assert!(expression("3)+1").is_err());
}