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This commit is contained in:
greg 2015-08-05 22:30:25 -07:00
parent 0da7f7e3a1
commit 7d6f946e22
1 changed files with 22 additions and 28 deletions
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50
src/parser.rs
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@ -1,5 +1,6 @@
use std::slice::Iter;
use std::iter::Peekable;
use std::collections::HashMap;
use tokenizer::{Token, Kw};
use tokenizer::Token::*;
@ -32,6 +33,14 @@ macro_rules! expect {
})
}
macro_rules! expect_parse {
($parse_fn:ident, $tokens:ident) => (
match $parse_fn($tokens) {
err@ParseResult::Err(_) => return err,
ParseResult::Ok(ast) => ast
})
}
fn expect_token(tok: Token, tokens: &mut Tokens) -> bool {
if let Some(n) = tokens.next() {
let next = (*n).clone();
@ -73,11 +82,7 @@ fn statements(tokens: &mut Tokens) -> ParseResult {
let mut statements = Vec::new();
let initial_statement = match statement(tokens) {
err@ParseResult::Err(_) => return err,
ParseResult::Ok(ast) => ast
};
let initial_statement = expect_parse!(statement, tokens);
statements.push(initial_statement);
loop {
@ -145,17 +150,10 @@ fn expression(tokens: &mut Tokens) -> ParseResult {
fn if_expression(tokens: &mut Tokens) -> ParseResult {
expect!(Keyword(Kw::If), tokens);
let if_clause = match expression(tokens) {
err@ParseResult::Err(_) => return err,
ParseResult::Ok(ast) => ast
};
let if_clause = expect_parse!(expression, tokens);
expect!(Keyword(Kw::Then), tokens);
let then_clause = match expression(tokens) {
err@ParseResult::Err(_) => return err,
ParseResult::Ok(ast) => ast
};
let then_clause = expect_parse!(expression, tokens);
let else_clause = match tokens.peek().map(|i| i.clone()) {
Some(&Keyword(Kw::Else)) => {
@ -179,16 +177,11 @@ fn if_expression(tokens: &mut Tokens) -> ParseResult {
fn while_expression(tokens: &mut Tokens) -> ParseResult {
expect!(Keyword(Kw::While), tokens);
let while_expression = match expression(tokens) {
err@ParseResult::Err(_) => return err,
ParseResult::Ok(ast) => ast
};
let while_expression = expect_parse!(expression, tokens);
expect!(Separator, tokens);
let statements = match statements(tokens) {
err@ParseResult::Err(_) => return err,
ParseResult::Ok(ast) => ast
};
let statements = expect_parse!(statements, tokens);
expect!(Keyword(Kw::End), tokens);
@ -201,10 +194,7 @@ fn while_expression(tokens: &mut Tokens) -> ParseResult {
fn binop_expression(precedence: i32, tokens: &mut Tokens) -> ParseResult {
//TODO left needs to match on an identifiers vs. a prefix operator and return *that* AST
let mut left: AST = match simple_expression(tokens) {
err@ParseResult::Err(_) => return err,
ParseResult::Ok(ast) => ast
};
let mut left: AST = expect_parse!(simple_expression, tokens);
loop {
let lookahead: Option<&Token> = tokens.peek().map(|i| i.clone());
@ -251,8 +241,12 @@ fn get_binop_precedence(token: &Token) -> Option<i32> {
match &identifier_str[..] {
"+" => Some(20),
"-" => Some(20),
"*" => Some(40),
"/" => Some(40),
"*" => Some(30),
"/" => Some(30),
"==" => Some(10),
">" => Some(15),
"<" => Some(15),
"<=>" => Some(15),
_ => None
}
}