95 lines
2.2 KiB
Rust
95 lines
2.2 KiB
Rust
|
use nom::{
|
||
|
|
branch::alt,
|
||
|
|
bytes::complete::tag,
|
||
|
|
character::complete::char,
|
||
|
|
character::complete::{digit1 as digit, space0 as space},
|
||
|
|
combinator::map_res,
|
||
|
|
multi::fold_many0,
|
||
|
|
sequence::{delimited, pair},
|
||
|
|
IResult,
|
||
|
|
};
|
||
|
|
|
||
|
|
// Parser definition
|
||
|
|
|
||
|
|
use std::str::FromStr;
|
||
|
|
|
||
|
|
// We parse any expr surrounded by parens, ignoring all whitespaces around those
|
||
|
|
fn parens(i: &str) -> IResult<&str, i64> {
|
||
|
|
delimited(space, delimited(tag("("), expr, tag(")")), space)(i)
|
||
|
|
}
|
||
|
|
|
||
|
|
// 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
|
||
|
|
fn factor(i: &str) -> IResult<&str, i64> {
|
||
|
|
alt((
|
||
|
|
map_res(delimited(space, digit, space), FromStr::from_str),
|
||
|
|
parens,
|
||
|
|
))(i)
|
||
|
|
}
|
||
|
|
|
||
|
|
// 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
|
||
|
|
fn term(i: &str) -> IResult<&str, i64> {
|
||
|
|
let (i, init) = factor(i)?;
|
||
|
|
|
||
|
|
fold_many0(
|
||
|
|
pair(alt((char('*'), char('/'))), factor),
|
||
|
|
move || init,
|
||
|
|
|acc, (op, val): (char, i64)| {
|
||
|
|
if op == '*' {
|
||
|
|
acc * val
|
||
|
|
} else {
|
||
|
|
acc / val
|
||
|
|
}
|
||
|
|
},
|
||
|
|
)(i)
|
||
|
|
}
|
||
|
|
|
||
|
|
fn expr(i: &str) -> IResult<&str, i64> {
|
||
|
|
let (i, init) = term(i)?;
|
||
|
|
|
||
|
|
fold_many0(
|
||
|
|
pair(alt((char('+'), char('-'))), term),
|
||
|
|
move || init,
|
||
|
|
|acc, (op, val): (char, i64)| {
|
||
|
|
if op == '+' {
|
||
|
|
acc + val
|
||
|
|
} else {
|
||
|
|
acc - val
|
||
|
|
}
|
||
|
|
},
|
||
|
|
)(i)
|
||
|
|
}
|
||
|
|
|
||
|
|
#[test]
|
||
|
|
fn factor_test() {
|
||
|
|
assert_eq!(factor("3"), Ok(("", 3)));
|
||
|
|
assert_eq!(factor(" 12"), Ok(("", 12)));
|
||
|
|
assert_eq!(factor("537 "), Ok(("", 537)));
|
||
|
|
assert_eq!(factor(" 24 "), Ok(("", 24)));
|
||
|
|
}
|
||
|
|
|
||
|
|
#[test]
|
||
|
|
fn term_test() {
|
||
|
|
assert_eq!(term(" 12 *2 / 3"), Ok(("", 8)));
|
||
|
|
assert_eq!(term(" 2* 3 *2 *2 / 3"), Ok(("", 8)));
|
||
|
|
assert_eq!(term(" 48 / 3/2"), Ok(("", 8)));
|
||
|
|
}
|
||
|
|
|
||
|
|
#[test]
|
||
|
|
fn expr_test() {
|
||
|
|
assert_eq!(expr(" 1 + 2 "), Ok(("", 3)));
|
||
|
|
assert_eq!(expr(" 12 + 6 - 4+ 3"), Ok(("", 17)));
|
||
|
|
assert_eq!(expr(" 1 + 2*3 + 4"), Ok(("", 11)));
|
||
|
|
}
|
||
|
|
|
||
|
|
#[test]
|
||
|
|
fn parens_test() {
|
||
|
|
assert_eq!(expr(" ( 2 )"), Ok(("", 2)));
|
||
|
|
assert_eq!(expr(" 2* ( 3 + 4 ) "), Ok(("", 14)));
|
||
|
|
assert_eq!(expr(" 2*2 / ( 5 - 1) + 3"), Ok(("", 4)));
|
||
|
|
}
|