Added Keyword lexical class

src/parser.rs

@@ -1,7 +1,7 @@
 use std::slice::Iter;
 use std::iter::Peekable;
 
-use tokenizer::{Token};
+use tokenizer::{Token, Kw};
 use tokenizer::Token::*;
 
 #[derive(Debug)]
@@ -39,6 +39,7 @@ fn expect_token(tok: Token, tokens: &mut Tokens) -> bool {
             (NumLiteral(_), NumLiteral(_)) => true,
             (StrLiteral(_), StrLiteral(_)) => true,
             (Identifier(ref i1), Identifier(ref i2)) => i1 == i2,
+            (Keyword(k1), Keyword(k2)) => k1 == k2,
             _ => false
         }
     }
@@ -60,7 +61,7 @@ pub fn parse(input: Vec<Token>) -> ParseResult {
 
 
 fn let_expression(input: &mut Tokens) -> ParseResult {
-    expect!(Identifier("let".to_string()), input);
+    expect!(Keyword(Kw::Let), input);
     if let Some(&Identifier(ref name)) = input.next() {
         if let Some(&Identifier(ref s)) = input.next() {
             if s == "=" {

src/tokenizer.rs

@@ -7,8 +7,21 @@ pub enum Token {
     Comma,
     NumLiteral(f64),
     StrLiteral(String),
-    Identifier(String)
-    /* Keyword(Keyword) */ //implement in future
+    Identifier(String),
+    Keyword(Kw)
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Kw {
+    If,
+    Then,
+    Else,
+    While,
+    Do,
+    End,
+    Let,
+    Fn,
+    Null
 }
 
 pub fn tokenize(input: &str) -> Vec<Token> {
@@ -67,10 +80,18 @@ pub fn tokenize(input: &str) -> Vec<Token> {
 
             match buffer.parse::<f64>() {
                 Ok(f) => tokens.push(Token::NumLiteral(f)),
-                _ => tokens.push(Token::Identifier(buffer))
+                _ => tokens.push(handle_identifier(buffer))
             }
         }
     }
     tokens.push(Token::EOF);
     tokens
 }
+
+fn handle_identifier(identifier: String) -> Token {
+    if identifier == "let" {
+        return Token::Keyword(Kw::Let);
+    }
+
+    return Token::Identifier(identifier);
+}