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#[macro_use]
extern crate nom;
use nom::digit;
use nom::types::CompleteStr;
// Parser definition
use std::str::FromStr;
// We parse any expr surrounded by parens, ignoring all whitespaces around those
named!(parens<CompleteStr, i64>, ws!(delimited!( tag!("("), expr, tag!(")") )) );
// We transform an integer string into a i64, ignoring surrounding whitespaces
// We look for a digit suite, and try to convert it.
// If either str::from_utf8 or FromStr::from_str fail,
// we fallback to the parens parser defined above
named!(factor<CompleteStr, i64>, alt!(
map_res!(
ws!(digit),
|s:CompleteStr| { FromStr::from_str(s.0) }
)
| parens
)
);
// We read an initial factor and for each time we find
// a * or / operator followed by another factor, we do
// the math by folding everything
named!(term <CompleteStr, i64>, do_parse!(
init: factor >>
res: fold_many0!(
pair!(alt!(char!('*') | char!('/')), factor),
init,
|acc, (op, val): (char, i64)| {
if op == '*' { acc * val } else { acc / val }
}
) >>
(res)
)
);
named!(expr <CompleteStr, i64>, do_parse!(
init: term >>
res: fold_many0!(
pair!(alt!(char!('+') | char!('-')), term),
init,
|acc, (op, val): (char, i64)| {
if op == '+' { acc + val } else { acc - val }
}
) >>
(res)
)
);
#[test]
fn factor_test() {
assert_eq!(factor(CompleteStr("3")), Ok((CompleteStr(""), 3)));
assert_eq!(factor(CompleteStr(" 12")), Ok((CompleteStr(""), 12)));
assert_eq!(factor(CompleteStr("537 ")), Ok((CompleteStr(""), 537)));
assert_eq!(factor(CompleteStr(" 24 ")), Ok((CompleteStr(""), 24)));
}
#[test]
fn term_test() {
assert_eq!(term(CompleteStr(" 12 *2 / 3")), Ok((CompleteStr(""), 8)));
assert_eq!(
term(CompleteStr(" 2* 3 *2 *2 / 3")),
Ok((CompleteStr(""), 8))
);
assert_eq!(term(CompleteStr(" 48 / 3/2")), Ok((CompleteStr(""), 8)));
}
#[test]
fn expr_test() {
assert_eq!(expr(CompleteStr(" 1 + 2 ")), Ok((CompleteStr(""), 3)));
assert_eq!(
expr(CompleteStr(" 12 + 6 - 4+ 3")),
Ok((CompleteStr(""), 17))
);
assert_eq!(expr(CompleteStr(" 1 + 2*3 + 4")), Ok((CompleteStr(""), 11)));
}
#[test]
fn parens_test() {
assert_eq!(expr(CompleteStr(" ( 2 )")), Ok((CompleteStr(""), 2)));
assert_eq!(
expr(CompleteStr(" 2* ( 3 + 4 ) ")),
Ok((CompleteStr(""), 14))
);
assert_eq!(
expr(CompleteStr(" 2*2 / ( 5 - 1) + 3")),
Ok((CompleteStr(""), 4))
);
}
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