79 lines
2.2 KiB
Rust
79 lines
2.2 KiB
Rust
use std::slice::Iter;
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use tokenizer::{Token};
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use tokenizer::Token::*;
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#[derive(Debug)]
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pub enum AST {
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Name(String),
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LangString(String),
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Number(f64),
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BinOp(Box<AST>, Box<AST>, Box<AST>),
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Binding(String, Box<AST>)
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}
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pub enum ParseResult {
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Ok(AST),
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Err(String)
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}
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pub fn parse(input: Vec<Token>) -> ParseResult {
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let mut tokens = input.iter();
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if let ParseResult::Ok(ast) = let_expression(&mut tokens) {
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if expect(EOF, &mut tokens) {
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return ParseResult::Ok(ast);
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}
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}
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return ParseResult::Err("Bad parse".to_string());
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}
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fn expect(tok: Token, tokens: &mut Iter<Token>) -> bool {
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if let Some(n) = tokens.next() {
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let next = (*n).clone();
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return match (tok, next) {
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(EOF, EOF) => true,
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(Separator, Separator) => true,
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(LParen, LParen) => true,
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(RParen, RParen) => true,
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(Comma, Comma) => true,
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(NumLiteral(_), NumLiteral(_)) => true,
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(StrLiteral(_), StrLiteral(_)) => true,
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(Identifier(ref i1), Identifier(ref i2)) => i1 == i2,
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_ => false
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}
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}
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return false;
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}
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fn let_expression<'a>(input: &mut Iter<Token>) -> ParseResult {
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if expect(Identifier("let".to_string()), input) {
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if let Some(&Identifier(ref name)) = input.next() {
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if let Some(&Identifier(ref s)) = input.next() {
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if s == "=" {
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let next = input.next();
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if let Some(&Identifier(ref value)) = next {
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let ast = AST::Binding(name.clone(), Box::new(AST::Name(value.clone())));
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return ParseResult::Ok(ast);
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}
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if let Some(&StrLiteral(ref value)) = next {
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let ast = AST::Binding(name.clone(), Box::new(AST::LangString(value.clone())));
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return ParseResult::Ok(ast);
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}
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if let Some(&NumLiteral(n)) = next {
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let ast = AST::Binding(name.clone(), Box::new(AST::Number(n)));
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return ParseResult::Ok(ast);
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}
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}
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}
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}
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}
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return ParseResult::Err("Bad parse".to_string());
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}
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