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extern crate peg;
use arithmetic::expression;
peg::parser!( grammar arithmetic() for str {
pub rule expression() -> i64
= sum()
rule sum() -> i64
= l:product() "+" r:product() { l+r }
/ product()
rule product() -> i64
= l:atom() "*" r:atom() { l*r }
/ atom()
rule atom() -> i64
= number()
/ "(" v:sum() ")" { v }
rule number() -> i64
= n:$(['0'..='9']+) { n.parse().unwrap() }
});
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());
}
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