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|
use nom::{
IResult,
Parser,
branch::alt,
multi::many0,
bytes::complete::{tag, take_while1},
character::complete::multispace1,
};
use crate::sexp::{SExp, SExp::*, SLeaf::*, util::*};
#[derive(Debug,PartialEq)]
pub enum Token {
ParOpen,
ParClose,
Num(i32),
Sym(String),
Whitespace(String),
}
use Token::*;
use crate::parse::util::*;
fn parse_token(s: &str) -> IResult<&str, Token> {
alt((
tag("(").map(|_| ParOpen),
tag(")").map(|_| ParClose),
multispace1.map(whitespace),
nom::character::complete::i32.map(Num),
take_while1(|c| !(" \n\t()".contains(c))).map(sym),
)).parse(s)
}
fn tokenize(s: &str) -> Result<Vec<Token>, String> {
match many0(parse_token).parse(s) {
Ok(("", res)) => Ok(res),
Ok((rest, _)) => Err(format!("all data should be tokenizable, '{rest}' was not")),
Err(e) => Err(e.to_string()),
}
}
fn tokens_to_ast(tokens: Vec<Token>) -> Result<SExp, String> {
todo!()
}
#[cfg(test)]
mod private_parsing_tests {
use super::{*, parse_token};
#[test]
fn test_parse_token() {
assert_eq!(parse_token("()"), Ok((")", ParOpen)));
assert_eq!(parse_token(")"), Ok(("", ParClose)));
assert_eq!(parse_token(" \t\n"), Ok(("", whitespace(" \t\n"))));
assert_eq!(parse_token("1 23"), Ok((" 23", Num(1))));
assert_eq!(parse_token("23"), Ok(("", Num(23))));
assert_eq!(parse_token("Nil a"), Ok((" a", sym("Nil"))));
assert_eq!(parse_token("a"), Ok(("", sym("a"))));
assert!(parse_token("").is_err())
}
#[test]
fn test_tokenize() {
assert_eq!(
tokenize("(+ 1 2 (\t\n a)").unwrap(),
vec![
ParOpen,
sym("+"), whitespace(" "),
Num(1), whitespace(" "),
Num(2), whitespace(" "),
ParOpen, whitespace("\t\n "),
sym("a"),
ParClose
]
);
}
#[test]
fn test_tokens_to_ast() {
// Syms are parsed to vars,
// and everything is wrapped in an extra layer of scons
// so that multi-expression programs can be returned
// as one single SExp.
assert_eq!(
tokens_to_ast(vec![sym("a")]),
Ok(scons(var("a"), Nil))
);
// Lists are pased to scons linked lists
assert_eq!(
tokens_to_ast(vec![
ParOpen,
sym("a"), whitespace(" "),
sym("b"), whitespace(" "),
sym("c"), whitespace(" "),
ParClose,
]),
Ok(scons(scons(var("a"), scons(var("b"), scons(var("c"), Nil))), Nil))
);
// Nesting should work.
assert_eq!(
tokens_to_ast(vec![
ParOpen,
sym("a"), whitespace(" "),
ParOpen,
sym("b"), whitespace(" "),
sym("c"), whitespace(" "),
ParClose, whitespace(" "),
sym("d"),
ParClose
]),
Ok(
scons(scons(var("a"), scons(
scons(var("b"), scons(var("c"), Nil))
, scons(var("d"), Nil))), Nil)
)
);
// Multiple expressions should be parseable
assert_eq!(
tokens_to_ast(vec![
ParOpen,
sym("a"),
ParClose,
sym("b"),
ParOpen,
sym("c"),
ParClose,
]),
Ok(scons(
scons(var("a"), Nil),
scons(var("b"),
scons(scons(var("c"), Nil), Nil))))
);
// Operators are parsed correctly
assert_eq!(
tokens_to_ast(vec![
ParOpen,
sym("+"), whitespace(" "),
sym("-"), whitespace(" "),
sym("*"), whitespace(" "),
sym("/"),
ParClose
]),
Ok(scons(
scons(Add,
scons(Sub,
scons(Mul,
scons(Div,
Nil)))), Nil))
);
// Integers are parsed correctly
assert_eq!(
tokens_to_ast(vec![Num(5)]),
Ok(scons(Int(5), Nil))
);
// Nil can be parsed
assert_eq!(
tokens_to_ast(vec![ParOpen,ParClose]),
Ok(scons(Nil, Nil))
);
// Quote can be parsed
assert_eq!(
tokens_to_ast(vec![
ParOpen,
sym("quote"), whitespace(" "),
sym("a"), whitespace(" "),
sym("b"), whitespace(" ")
]),
Ok(scons(Quote, scons(var("a"), scons(var("b"), Nil))))
);
}
#[test]
fn test_tokens_to_ast_failing() {
assert!(
tokens_to_ast(vec![ParClose]).is_err(),
"Invalid parentheses should fail"
);
assert!(
tokens_to_ast(vec![ParOpen]).is_err(),
"Invalid parentheses should fail"
);
assert!(
tokens_to_ast(vec![ParClose, ParOpen]).is_err(),
"Invalid parentheses should fail"
);
assert!(
tokens_to_ast(vec![ParOpen, ParOpen, ParClose]).is_err(),
"Invalid parentheses should fail"
);
assert!(
tokens_to_ast(vec![Num(1), sym("a")]).is_err(),
"Having a symbol starting with a number should fail."
);
assert!(
tokens_to_ast(vec![sym("quote"), sym("a")]).is_err(),
"There should be whitespace between quote and other symbols"
);
}
}
|
