From 67eafba97ad5a0c183ebe1d82e434fb4e8cb2551 Mon Sep 17 00:00:00 2001 From: greg Date: Wed, 22 Jul 2015 03:28:26 -0700 Subject: [PATCH] Put expect into early return macro --- src/parser.rs | 47 ++++++++++++++++++++++++++--------------------- 1 file changed, 26 insertions(+), 21 deletions(-) diff --git a/src/parser.rs b/src/parser.rs index 0d8c9bd..65299db 100644 --- a/src/parser.rs +++ b/src/parser.rs @@ -17,20 +17,26 @@ pub enum ParseResult { Err(String) } +macro_rules! expect { + ($tok:expr, $tokens:expr) => ( if !expect_token($tok, $tokens) { + println!("yo hitting"); + return ParseResult::Err(format!("Expected {:?}", $tok)); + }) +} + pub fn parse(input: Vec) -> ParseResult { let mut tokens = input.iter(); if let ParseResult::Ok(ast) = let_expression(&mut tokens) { - if expect(EOF, &mut tokens) { - return ParseResult::Ok(ast); - } + expect!(EOF, &mut tokens); + return ParseResult::Ok(ast); } return ParseResult::Err("Bad parse".to_string()); } -fn expect(tok: Token, tokens: &mut Iter) -> bool { +fn expect_token(tok: Token, tokens: &mut Iter) -> bool { if let Some(n) = tokens.next() { let next = (*n).clone(); return match (tok, next) { @@ -50,25 +56,24 @@ fn expect(tok: Token, tokens: &mut Iter) -> bool { } fn let_expression<'a>(input: &mut Iter) -> ParseResult { - if expect(Identifier("let".to_string()), input) { - if let Some(&Identifier(ref name)) = input.next() { - if let Some(&Identifier(ref s)) = input.next() { - if s == "=" { - let next = input.next(); - if let Some(&Identifier(ref value)) = next { - let ast = AST::Binding(name.clone(), Box::new(AST::Name(value.clone()))); - return ParseResult::Ok(ast); - } + expect!(Identifier("let".to_string()), input); + if let Some(&Identifier(ref name)) = input.next() { + if let Some(&Identifier(ref s)) = input.next() { + if s == "=" { + let next = input.next(); + if let Some(&Identifier(ref value)) = next { + let ast = AST::Binding(name.clone(), Box::new(AST::Name(value.clone()))); + return ParseResult::Ok(ast); + } - if let Some(&StrLiteral(ref value)) = next { - let ast = AST::Binding(name.clone(), Box::new(AST::LangString(value.clone()))); - return ParseResult::Ok(ast); - } + if let Some(&StrLiteral(ref value)) = next { + let ast = AST::Binding(name.clone(), Box::new(AST::LangString(value.clone()))); + return ParseResult::Ok(ast); + } - if let Some(&NumLiteral(n)) = next { - let ast = AST::Binding(name.clone(), Box::new(AST::Number(n))); - return ParseResult::Ok(ast); - } + if let Some(&NumLiteral(n)) = next { + let ast = AST::Binding(name.clone(), Box::new(AST::Number(n))); + return ParseResult::Ok(ast); } } }