Add characters module

src/lexer.rs

@@ -1,41 +1,6 @@
 //! # Lexer
 
-mod characters {
-    use std::collections::HashSet;
-    use std::iter::FromIterator;
-    
-    pub type CharSet = HashSet<char>;
-
-    pub fn ascii_letters() -> CharSet {
-        let letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".chars();
-        return CharSet::from_iter(letters);
-    }
-
-    pub fn ascii_digits() -> CharSet {
-        let digits = "1234567890".chars();
-        return CharSet::from_iter(digits);
-    }
-
-    pub fn identifier_initials() -> CharSet {
-        let letters = ascii_letters();
-        let extras = CharSet::from_iter("!$%&*/:<=>?~_^".chars());
-        let mut initials = CharSet::new();
-        initials.extend(letters.iter());
-        initials.extend(extras.iter());
-        return initials;
-    }
-
-    pub fn identifier_subsequents() -> CharSet {
-        let initials = identifier_initials();
-        let digits = ascii_digits();
-        let extras = CharSet::from_iter(".+-".chars());
-        let mut subsequents = CharSet::new();
-        subsequents.extend(initials.iter());
-        subsequents.extend(digits.iter());
-        subsequents.extend(extras.iter());
-        return subsequents;
-    }
-}
+use characters;
 
 enum Kind {
     LeftParen,
@@ -48,6 +13,21 @@ struct Token {
     value: String,
 }
 
+struct Lexer {
+    input: str,
+}
+
+impl Lexer {
+}
+
+impl Iterator for Lexer {
+    type Item = Token;
+
+    fn next(&mut self) -> Option<Token> {
+        None
+    }
+}
+
 pub fn hello(person: &str) {
     println!("Hello, {}!", person);
     for (idx, c) in person.char_indices() {