53 lines
1.3 KiB
Rust
53 lines
1.3 KiB
Rust
use crate::lexer::Token;
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use crate::lexer::Tokens;
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#[derive(Debug, Clone)]
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pub enum Datum {
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Boolean(bool),
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Number(i64),
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Symbol(String),
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List(Vec<Datum>),
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Procedure(fn(Vec<Datum>) -> Datum),
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Unspecified,
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}
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pub fn make_symbol(s: &str) -> Datum {
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Datum::Symbol(s.to_string())
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}
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impl Default for Datum {
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fn default() -> Self {
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Datum::Unspecified
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}
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}
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pub fn parse(tokens: Tokens) -> Datum {
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let (datum, _) = parse_datum(&tokens, 0);
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datum
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}
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fn parse_datum(tokens: &Tokens, ix: usize) -> (Datum, usize) {
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match &tokens[ix] {
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Token::Identifier(s) => (Datum::Symbol(s.to_string()), ix + 1),
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Token::Boolean(b) => (Datum::Boolean(*b), ix + 1),
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Token::Number(n) => (Datum::Number(*n), ix + 1),
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Token::LeftRoundBracket => parse_list(tokens, ix + 1),
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_ => panic!("Unexpected token {:?}", tokens[ix]),
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}
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}
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pub fn parse_list(tokens: &Tokens, mut ix: usize) -> (Datum, usize) {
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let mut datums = vec![];
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while ix < tokens.len() && tokens[ix] != Token::RightRoundBracket {
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let (datum, new_ix) = parse_datum(tokens, ix);
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datums.push(datum);
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ix = new_ix;
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}
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if ix == tokens.len() {
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panic!("PARSE_LIST -- missing closing bracket {:?}", tokens)
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}
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(Datum::List(datums), ix + 1)
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}
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