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Roughing out pratt parser logic

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This commit is contained in:
Andy Grove 2018-09-01 08:39:27 -06:00
parent e6e9c8d2cc
commit 72cff632c1
5 changed files with 91 additions and 46 deletions
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67
src/parser.rs
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@ -1,5 +1,8 @@
use std::cmp::PartialEq;
use std::fmt::Debug;
use std::rc::Rc;
use std::str::Chars;
use std::iter::Peekable;
use super::tokenizer::*;
@ -105,41 +108,47 @@ impl<TokenType> From<TokenizerError<TokenType>> for ParserError<TokenType>
pub trait SQLParser<TokenType, ExprType>
where TokenType: Debug + PartialEq, ExprType: Debug + PartialEq {
where TokenType: Debug + PartialEq, ExprType: Debug {
/// parse the prefix and stop once an infix operator is reached
fn parse_prefix(&mut self) -> Result<Box<SQLExpr<ExprType>>, ParserError<TokenType>> ;
/// parse the next infix expression, returning None if the precedence has changed
fn parse_infix(&mut self, left: SQLExpr<ExprType>) -> Result<Option<Box<SQLExpr<ExprType>>>, ParserError<TokenType>>;
fn parse_infix(&mut self, left: &SQLExpr<ExprType>, precedence: usize) -> Result<Option<Box<SQLExpr<ExprType>>>, ParserError<TokenType>>;
}
struct PrattParser<'a, TokenType, ExprType> {
chars: Peekable<Chars<'a>>,
tokenizer: Rc<SQLTokenizer<TokenType>>,
parser: SQLParser<TokenType, ExprType>
}
impl<'a, TokenType, ExprType> PrattParser<'a, TokenType, ExprType>
where TokenType: Debug + PartialEq, ExprType: Debug {
fn parse_expr(&mut self) -> Result<Box<SQLExpr<ExprType>>, ParserError<TokenType>> {
let precedence: usize = 0;
let mut expr = self.parser.parse_prefix()?;
while let Some(token) = self.tokenizer.peek_token(&mut self.chars)? {
let next_precedence = self.tokenizer.precedence(&token);
if precedence >= next_precedence {
break;
}
expr = self.parser.parse_infix(&expr, next_precedence)?.unwrap(); //TODO: fix me
}
Ok(expr)
}
}
//
//
//struct GenericParser {
// tokenizer: SQLTokenizer
//}
//
//impl GenericParser {
//
// fn parse_expr(&mut self, precedence: u8) -> Result<Box<SQLExpr>, ParserError> {
//
// let mut expr = self.parse_prefix()?;
//
// // loop while there are more tokens and until the precedence changes
// while let Some(token) = self.tokenizer.peek_token()? {
//
// let next_precedence = self.get_precedence(&token);
//
// if precedence >= next_precedence {
// break;
// }
//
// expr = self.parse_infix(expr, next_precedence)?;
// }
//
// Ok(expr)
// }
//
// fn parse_prefix(&mut self) -> Result<Box<SQLExpr>, ParserError> {
//
// match self.tokenizer.peek_token()? {