Add characters module

src/characters.rs

@@ -0,0 +1,67 @@
+//! Characters
+//!
+//! Utilities for dealing with chars of various sorts.
+
+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;
+}
+
+pub trait RelativeIndexable {
+    fn index_before(&self, &usize) -> usize;
+    fn index_after(&self, &usize) -> usize;
+}
+
+impl RelativeIndexable for str {
+    fn index_before(&self, index: &usize) -> usize {
+        let mut prev_index = index - 1;
+        if prev_index <= 0 {
+            return 0;
+        }
+        while !self.is_char_boundary(prev_index) {
+            prev_index -= 1;
+        }
+        return prev_index;
+    }
+
+    fn index_after(&self, index: &usize) -> usize {
+        let mut next_index = index + 1;
+        if next_index > self.len() {
+            return self.len();
+        }
+        while !self.is_char_boundary(next_index) {
+            next_index += 1;
+        }
+        return next_index;
+    }
+}

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() {

src/main.rs

@@ -1,3 +1,4 @@
+mod characters;
 mod lexer;
 
 fn main() {