#[macro_use]
extern crate nom;
use nom::digit;
use nom::types::CompleteByteSlice;
use std::str;
use std::str::FromStr;
use self::Operator::*;
enum Operator {
Slash,
Star,
}
impl Operator {
fn to_str(&self) -> &'static str {
match *self {
Slash => "/",
Star => "*",
}
}
}
named_args!(operator(op: Operator) <CompleteByteSlice, CompleteByteSlice>,
tag!(op.to_str())
);
named_args!(brackets<'a>(open_tag: &str, close_tag: &str) <CompleteByteSlice<'a>, i64>,
ws!(delimited!( tag!(open_tag), expr, tag!(close_tag) )) );
fn complete_byte_slice_to_str<'a>(s: CompleteByteSlice<'a>) -> Result<&'a str, str::Utf8Error> {
str::from_utf8(s.0)
}
named!(factor<CompleteByteSlice, i64>, alt!(
map_res!(
map_res!(
ws!(digit),
complete_byte_slice_to_str
),
FromStr::from_str
)
| call!(brackets, "(", ")")
)
);
named!(term <CompleteByteSlice, i64>, do_parse!(
init: factor >>
res: fold_many0!(
pair!(alt!(call!(operator, Star) | call!(operator, Slash)), factor),
init,
|acc, (op, val): (CompleteByteSlice, i64)| {
if ((op.0)[0] as char) == '*' { acc * val } else { acc / val }
}
) >>
(res)
)
);
named!(expr <CompleteByteSlice, i64>, do_parse!(
init: term >>
res: fold_many0!(
pair!(alt!(tag!("+") | tag!("-")), term),
init,
|acc, (op, val): (CompleteByteSlice, i64)| {
if ((op.0)[0] as char) == '+' { acc + val } else { acc - val }
}
) >>
(res)
)
);
#[test]
fn factor_test() {
assert_eq!(factor(CompleteByteSlice(b"3")), Ok((CompleteByteSlice(b""), 3)));
assert_eq!(factor(CompleteByteSlice(b" 12")), Ok((CompleteByteSlice(b""), 12)));
assert_eq!(factor(CompleteByteSlice(b"537 ")), Ok((CompleteByteSlice(b""), 537)));
assert_eq!(factor(CompleteByteSlice(b" 24 ")), Ok((CompleteByteSlice(b""), 24)));
}
#[test]
fn term_test() {
assert_eq!(term(CompleteByteSlice(b" 12 *2 / 3")), Ok((CompleteByteSlice(b""), 8)));
assert_eq!(term(CompleteByteSlice(b" 2* 3 *2 *2 / 3")), Ok((CompleteByteSlice(b""), 8)));
assert_eq!(term(CompleteByteSlice(b" 48 / 3/2")), Ok((CompleteByteSlice(b""), 8)));
}
#[test]
fn expr_test() {
assert_eq!(expr(CompleteByteSlice(b" 1 + 2 ")), Ok((CompleteByteSlice(b""), 3)));
assert_eq!(expr(CompleteByteSlice(b" 12 + 6 - 4+ 3")), Ok((CompleteByteSlice(b""), 17)));
assert_eq!(expr(CompleteByteSlice(b" 1 + 2*3 + 4")), Ok((CompleteByteSlice(b""), 11)));
}
#[test]
fn parens_test() {
assert_eq!(expr(CompleteByteSlice(b" ( 2 )")), Ok((CompleteByteSlice(b""), 2)));
assert_eq!(expr(CompleteByteSlice(b" 2* ( 3 + 4 ) ")), Ok((CompleteByteSlice(b""), 14)));
assert_eq!(expr(CompleteByteSlice(b" 2*2 / ( 5 - 1) + 3")), Ok((CompleteByteSlice(b""), 4)));
}