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use crate::token::Token;
/// The lexer for the Simple Object Machine.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Lexer {
pub(crate) chars: Vec<char>,
pub(crate) skip_comments: bool,
pub(crate) skip_whitespace: bool,
pub(crate) skip_separator: bool,
}
impl Lexer {
const SEPARATOR: &'static str = "----";
const PRIMITIVE: &'static str = "primitive";
/// Construct a new lexer.
pub fn new<T: AsRef<str>>(input: T) -> Lexer {
Lexer {
chars: input.as_ref().chars().rev().collect(),
skip_comments: false,
skip_whitespace: false,
skip_separator: false,
}
}
/// Configure the lexer on whether to skip whitespace or not.
pub fn skip_whitespace(mut self, value: bool) -> Lexer {
self.skip_whitespace = value;
self
}
/// Configure the lexer on whether to skip comments or not.
pub fn skip_comments(mut self, value: bool) -> Lexer {
self.skip_comments = value;
self
}
/// Consume the lexer and return the left-over text.
pub fn text(self) -> String {
self.chars.into_iter().rev().collect()
}
fn lex_string(&mut self) -> Option<String> {
let mut output = String::new();
self.chars.pop()?;
loop {
match self.chars.pop()? {
'\'' => break Some(output),
'\\' => match self.chars.pop()? {
't' => output.push('\t'),
'b' => output.push('\x08'),
'n' => output.push('\n'),
'r' => output.push('\r'),
'f' => output.push('\x12'),
'\'' => output.push('\''),
'\\' => output.push('\\'),
'0' => output.push('\0'),
_ => {}
},
ch => output.push(ch),
}
}
}
fn lex_comment(&mut self) -> Option<Token> {
let mut output = String::new();
self.chars.pop()?;
loop {
let ch = self.chars.pop()?;
if ch == '"' {
break if self.skip_comments {
self.next()
} else {
Some(Token::Comment(output))
};
} else {
output.push(ch);
}
}
}
fn lex_operator(&mut self) -> Option<Token> {
let iter = self.chars.iter().rev().copied();
let length = iter.take_while(|ch| Lexer::is_operator(*ch)).count();
match length {
0 => None,
1 => match self.chars.pop()? {
'~' => Some(Token::Not),
'&' => Some(Token::And),
'|' => Some(Token::Or),
'*' => Some(Token::Star),
'/' => Some(Token::Div),
'\\' => Some(Token::Mod),
'+' => Some(Token::Plus),
'=' => Some(Token::Equal),
'>' => Some(Token::More),
'<' => Some(Token::Less),
',' => Some(Token::Comma),
'@' => Some(Token::At),
'%' => Some(Token::Per),
'-' => Some(Token::Minus),
_ => None,
},
length => {
let mut operator = String::with_capacity(length);
for _ in 0..length {
operator.push(self.chars.pop()?);
}
Some(Token::OperatorSequence(operator))
}
}
}
fn lex_symbol(&mut self) -> Option<String> {
let mut symbol = String::new();
'outer: loop {
match self.chars.pop() {
Some(ch) if ch.is_alphabetic() => {
symbol.push(ch);
}
Some(ch) => {
self.chars.push(ch);
break;
}
None => {
break;
}
}
loop {
match self.chars.pop() {
Some(ch) if ch.is_alphanumeric() || ch == '_' => {
symbol.push(ch);
}
Some(':') => {
symbol.push(':');
break;
}
Some(ch) => {
self.chars.push(ch);
break 'outer;
}
None => {
break 'outer;
}
}
}
}
(!symbol.is_empty()).then_some(symbol)
}
fn is_operator(ch: char) -> bool {
matches!(
ch,
'~' | '&' | '|' | '*' | '/' | '\\' | '+' | '=' | '>' | '<' | ',' | '@' | '%' | '-'
)
}
}
impl Iterator for Lexer {
type Item = Token;
fn next(&mut self) -> Option<Self::Item> {
let mut iter = self.chars.iter().rev().copied().peekable();
let peeked = iter.peek().copied()?;
match peeked {
_ if peeked.is_whitespace() => {
let count = iter.take_while(|c| c.is_whitespace()).count();
for _ in 0..count {
self.chars.pop()?;
}
if self.skip_whitespace {
self.next()
} else {
Some(Token::Whitespace)
}
}
'\'' => self.lex_string().map(Token::LitString),
'"' => self.lex_comment(),
'[' => {
self.chars.pop()?;
Some(Token::NewBlock)
}
']' => {
self.chars.pop()?;
Some(Token::EndBlock)
}
'(' => {
self.chars.pop()?;
Some(Token::NewTerm)
}
')' => {
self.chars.pop()?;
Some(Token::EndTerm)
}
'#' => {
iter.next()?;
match iter.peek().copied() {
Some('\'') => {
self.chars.pop()?;
let symbol = self.lex_string()?;
Some(Token::LitSymbol(symbol))
}
Some('(') => {
self.chars.pop()?;
self.chars.pop()?;
Some(Token::NewArray)
}
Some(ch) if ch.is_alphabetic() => {
self.chars.pop()?;
let symbol = self.lex_symbol()?;
Some(Token::LitSymbol(symbol))
}
Some(ch) if Lexer::is_operator(ch) => {
let len = iter.take_while(|ch| Lexer::is_operator(*ch)).count();
let mut symbol = String::with_capacity(len);
self.chars.pop()?;
for _ in 0..len {
symbol.push(self.chars.pop()?);
}
Some(Token::LitSymbol(symbol))
}
_ => None,
}
}
'^' => {
self.chars.pop()?;
Some(Token::Exit)
}
'.' => {
self.chars.pop()?;
Some(Token::Period)
}
'-' => {
let sep_len = iter.take_while(|ch| *ch == '-').count();
if sep_len >= Lexer::SEPARATOR.len() {
for _ in 0..sep_len {
self.chars.pop()?;
}
if self.skip_separator {
self.next()
} else {
Some(Token::Separator)
}
} else {
self.lex_operator()
}
}
':' => {
iter.next()?;
if let Some('=') = iter.peek().copied() {
self.chars.pop()?;
self.chars.pop()?;
Some(Token::Assign)
} else {
self.chars.pop()?;
Some(Token::Colon)
}
}
_ if Lexer::is_operator(peeked) => self.lex_operator(),
_ => {
let primitive_len = Lexer::PRIMITIVE.chars().count();
if iter.take(primitive_len).eq(Lexer::PRIMITIVE.chars()) {
for _ in 0..primitive_len {
self.chars.pop()?;
}
Some(Token::Primitive)
} else if peeked.is_alphabetic() {
let mut ident: String = self
.chars
.iter()
.rev()
.copied()
.take_while(|c| c.is_alphanumeric() || *c == '_')
.collect();
let ident_len = ident.chars().count();
for _ in 0..ident_len {
self.chars.pop()?;
}
if let Some(':') = self.chars.last().copied() {
self.chars.pop()?;
ident.push(':');
Some(Token::Keyword(ident))
} else {
Some(Token::Identifier(ident))
}
} else if peeked.is_digit(10) {
let iter = self.chars.iter().rev().copied();
let int_part_len = iter.clone().take_while(|c| c.is_digit(10)).count();
let mut dec_iter = iter.clone().skip(int_part_len).peekable();
match (dec_iter.next(), dec_iter.peek()) {
(Some('.'), Some(ch)) if ch.is_digit(10) => {
let dec_part_len =
dec_iter.clone().take_while(|c| c.is_digit(10)).count();
let total_len = int_part_len + dec_part_len + 1;
let repr: String = iter.take(total_len).collect();
let number: f64 = repr.parse().ok()?;
for _ in 0..total_len {
self.chars.pop()?;
}
Some(Token::LitDouble(number))
}
_ => {
let repr: String = iter.take(int_part_len).collect();
for _ in 0..int_part_len {
self.chars.pop()?;
}
if let Ok(number) = repr.parse::<i64>() {
Some(Token::LitInteger(number))
} else {
Some(Token::LitBigInteger(repr))
}
}
}
} else {
None
}
}
}
}
}