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exception_itm_raw.rs
main_span_expr.rs 2.44 KiB
extern crate nom;
use nom::{
branch::alt,
bytes::complete::tag,
character::complete::{digit1, multispace0},
combinator::map,
sequence::{preceded, tuple},
IResult,
};
use nom_locate::LocatedSpan;
type Span<'a> = LocatedSpan<&'a str>;
#[derive(Debug, PartialEq)]
pub enum Op {
Add,
Sub,
}
type SpanOp<'a> = (Span<'a>, Op);
fn parse_op(i: Span) -> IResult<Span, SpanOp> {
alt((
map(tag("+"), |s| (s, Op::Add)),
map(tag("-"), |s| (s, Op::Sub)),
))(i)
}
#[derive(Debug, PartialEq)]
pub enum Expr<'a> {
Num(i32),
BinOp(Box<SpanExpr<'a>>, SpanOp<'a>, Box<SpanExpr<'a>>),
}
type SpanExpr<'a> = (Span<'a>, Expr<'a>);
pub fn parse_i32(i: Span) -> IResult<Span, SpanExpr> {
map(digit1, |digit_str: Span| {
(
digit_str,
Expr::Num(digit_str.fragment.parse::<i32>().unwrap()),
)
})(i)
}
fn parse_expr(i: Span) -> IResult<Span, SpanExpr> {
alt((
map(
tuple((parse_i32, preceded(multispace0, parse_op), parse_expr_ms)),
|(l, op, r)| (i, Expr::BinOp(Box::new(l), op, Box::new(r))),
),
parse_i32,
))(i)
}
fn parse_expr_ms(i: Span) -> IResult<Span, SpanExpr> {
preceded(multispace0, parse_expr)(i)
}
// dumps a Span into a String
fn dump_span(s: &Span) -> String {
format!(
"[line :{:?}, col:{:?}, {:?}]",
s.line,
s.get_column(),
s.fragment
)
}
// dumps a SpanExpr into a String
fn dump_expr(se: &SpanExpr) -> String {
let (s, e) = se;
match e {
Expr::Num(_) => dump_span(s),
Expr::BinOp(l, (sop, _), r) => {
format!("<{} {} {}>", dump_expr(l), dump_span(sop), dump_expr(r))
}
}
}
fn main() {
let (_, (s, e)) = parse_expr_ms(Span::new("\n 1+2 - \n3")).unwrap();
println!(
"span for the whole,expression: {:?}, \nline: {:?}, \ncolumn: {:?}",
s,
s.line,
s.get_column()
);
println!("raw e: {:?}", &e);
println!("pretty e: {}", dump_expr(&(s, e)));
}
// In this example, we have a `parse_expr_ms` is the "top" level parser.
// It consumes white spaces, allowing the location information to reflect the exact
// positions in the input file.
//
// The dump_expr will create a pretty printing of the expression with spans for
// each terminal. This will be useful for later for precise type error reporting.
//
// The extra field is not used, it can be used for metadata, such as filename.