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use nom::character::complete::{multispace0, multispace1};
use nom::error::{ErrorKind, ParseError};
use nom::{alt, char, complete, do_parse, many0, named, separated_list0, tag};
#[macro_use]
mod macros;
mod expr;
use crate::ast::{Decl, Fun, Ident};
pub use expr::expr;
pub type Error = nom::Err<nom::error::Error<String>>;
pub(crate) fn is_reserved(s: &str) -> bool {
matches!(s, "if" | "then" | "else" | "let" | "in" | "fn")
}
pub(crate) fn ident<'a, E>(i: &'a str) -> nom::IResult<&'a str, Ident, E>
where
E: ParseError<&'a str>,
{
let mut chars = i.chars();
if let Some(f) = chars.next() {
if f.is_alphabetic() || f == '_' {
let mut idx = 1;
for c in chars {
if !(c.is_alphanumeric() || c == '_') {
break;
}
idx += 1;
}
let id = &i[..idx];
if is_reserved(id) {
Err(nom::Err::Error(E::from_error_kind(i, ErrorKind::Satisfy)))
} else {
Ok((&i[idx..], Ident::from_str_unchecked(id)))
}
} else {
Err(nom::Err::Error(E::from_error_kind(i, ErrorKind::Satisfy)))
}
} else {
Err(nom::Err::Error(E::from_error_kind(i, ErrorKind::Eof)))
}
}
named!(fun_decl(&str) -> Decl, do_parse!(
complete!(tag!("fn"))
>> multispace0
>> name: ident
>> multispace1
>> args: separated_list0!(multispace1, ident)
>> multispace0
>> char!('=')
>> multispace0
>> body: expr
>> (Decl::Fun {
name,
body: Fun {
args,
body
}
})
));
named!(pub decl(&str) -> Decl, alt!(
fun_decl
));
named!(pub toplevel(&str) -> Vec<Decl>, many0!(decl));
#[cfg(test)]
mod tests {
use std::convert::TryInto;
use super::*;
use expr::tests::ident_expr;
#[test]
fn fn_decl() {
let res = test_parse!(decl, "fn id x = x");
assert_eq!(
res,
Decl::Fun {
name: "id".try_into().unwrap(),
body: Fun {
args: vec!["x".try_into().unwrap()],
body: *ident_expr("x"),
}
}
)
}
#[test]
fn multiple_decls() {
let res = test_parse!(
toplevel,
"fn id x = x
fn plus x y = x + y
fn main = plus (id 2) 7"
);
assert_eq!(res.len(), 3);
}
}
|
