schala/src/tokenizer.rs

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extern crate itertools;
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use std::iter::Peekable;
use std::str::Chars;
use self::itertools::Itertools;
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#[derive(Debug, Clone, PartialEq)]
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pub enum Token {
Newline,
Semicolon,
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LParen,
RParen,
Comma,
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Period,
Colon,
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NumLiteral(f64),
StrLiteral(String),
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Identifier(String),
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Operator(Op),
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Keyword(Kw),
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}
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#[derive(Debug, Clone, PartialEq)]
pub struct Op(pub String);
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#[derive(Debug, Clone, PartialEq)]
pub enum Kw {
If,
Then,
Else,
While,
End,
Let,
Fn,
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Null,
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}
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pub type TokenizeResult = Result<Vec<Token>, TokenizeError>;
#[derive(Debug)]
pub struct TokenizeError {
pub msg: String,
}
impl TokenizeError {
fn new(msg: &str) -> TokenizeError {
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TokenizeError { msg: msg.to_string() }
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}
}
fn is_digit(c: &char) -> bool {
c.is_digit(10)
}
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pub fn tokenize(input: &str) -> TokenizeResult {
use self::Token::*;
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let mut tokens = Vec::new();
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let mut iter: Peekable<Chars> = input.chars().peekable();
while let Some(c) = iter.next() {
if c == '#' {
while let Some(c) = iter.next() {
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if c == '\n' {
break;
}
}
}
let cur_tok = match c {
c if char::is_whitespace(c) && c != '\n' => continue,
'\n' => Newline,
';' => Semicolon,
'(' => LParen,
')' => RParen,
':' => Colon,
',' => Comma,
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'"' => try!(tokenize_str(&mut iter)),
c if !char::is_alphanumeric(c) => try!(tokenize_operator(c, &mut iter)),
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c @ '.' | c if is_digit(&c) => try!(tokenize_number_or_period(c, &mut iter)),
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c => try!(tokenize_identifier(c, &mut iter)),
};
tokens.push(cur_tok);
}
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Ok(tokens)
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}
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fn tokenize_str(iter: &mut Peekable<Chars>) -> Result<Token, TokenizeError> {
let mut buffer = String::new();
loop {
// TODO handle string escapes, interpolation
match iter.next() {
Some(x) if x == '"' => break,
Some(x) => buffer.push(x),
None => return Err(TokenizeError::new("Unclosed quote")),
}
}
Ok(Token::StrLiteral(buffer))
}
fn tokenize_operator(c: char, iter: &mut Peekable<Chars>) -> Result<Token, TokenizeError> {
let mut buffer = String::new();
buffer.push(c);
buffer.extend(iter.peeking_take_while(|x| !char::is_alphanumeric(*x) && !char::is_whitespace(*x)));
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Ok(Token::Operator(Op(buffer)))
}
fn tokenize_number_or_period(c: char, iter: &mut Peekable<Chars>) -> Result<Token, TokenizeError> {
if c == '.' && !iter.peek().map_or(false, is_digit) {
return Ok(Token::Period);
}
let mut buffer = String::new();
buffer.push(c);
buffer.extend(iter.peeking_take_while(|x| is_digit(x) || *x == '.'));
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match buffer.parse::<f64>() {
Ok(f) => Ok(Token::NumLiteral(f)),
Err(_) => Err(TokenizeError::new("Failed to parse digit")),
}
}
fn tokenize_identifier(c: char, iter: &mut Peekable<Chars>) -> Result<Token, TokenizeError> {
fn ends_identifier(c: &char) -> bool {
let c = *c;
char::is_whitespace(c) || is_digit(&c) || c == ';' || c == '(' || c == ')' ||
c == ',' || c == '.' || c == ',' || c == ':'
}
use self::Token::*;
let mut buffer = String::new();
buffer.push(c);
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buffer.extend(iter.peeking_take_while(|x| !ends_identifier(x)));
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Ok(match &buffer[..] {
"if" => Keyword(Kw::If),
"then" => Keyword(Kw::Then),
"else" => Keyword(Kw::Else),
"while" => Keyword(Kw::While),
"end" => Keyword(Kw::End),
"let" => Keyword(Kw::Let),
"fn" => Keyword(Kw::Fn),
"null" => Keyword(Kw::Null),
b => Identifier(b.to_string()),
})
}
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#[cfg(test)]
mod tests {
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use super::*;
use super::Token::*;
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macro_rules! token_test {
($input: expr, $output: pat, $ifexpr: expr) => {
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let tokens = tokenize($input).unwrap();
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match tokens[..] {
$output if $ifexpr => (),
_ => panic!("Actual output: {:?}", tokens),
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}
}
}
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#[test]
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fn basic_tokeniziation_tests() {
token_test!("let a = 3\n",
[Keyword(Kw::Let), Identifier(ref a), Operator(Op(ref b)), NumLiteral(3.0), Newline],
a == "a" && b == "=");
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token_test!("2+1",
[NumLiteral(2.0), Operator(Op(ref a)), NumLiteral(1.0)],
a == "+");
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token_test!("2 + 1",
[NumLiteral(2.0), Operator(Op(ref a)), NumLiteral(1.0)],
a == "+");
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token_test!("2.3*49.2",
[NumLiteral(2.3), Operator(Op(ref a)), NumLiteral(49.2)],
a == "*");
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assert!(tokenize("2.4.5").is_err());
}
#[test]
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fn string_test() {
token_test!("null + \"a string\"",
[Keyword(Kw::Null), Operator(Op(ref a)), StrLiteral(ref b)],
a == "+" && b == "a string");
}
#[test]
fn operator_test() {
token_test!("a *> b",
[Identifier(ref a), Operator(Op(ref b)), Identifier(ref c)],
a == "a" && b == "*>" && c == "b");
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}
}