diff --git a/src/lib.rs b/src/lib.rs
index f8a52ea..b5c4cab 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -27,11 +27,14 @@ use std::num::ParseIntError;
 use std::str::FromStr;
 use std::vec::Vec;
 
+mod tokenize;
 mod weekday;
 
 #[cfg(test)]
 mod tests;
 
+use tokenize::ParseState;
+use tokenize::Tokenizer;
 use weekday::day_of_week;
 use weekday::DayOfWeek;
 
@@ -89,210 +92,6 @@ impl From<ParseInternalError> for ParseError {
 type ParseResult<I> = Result<I, ParseError>;
 type ParseIResult<I> = Result<I, ParseInternalError>;
 
-pub struct Tokenizer {
-    token_stack: Vec<String>,
-    parse_string: String,
-}
-
-#[derive(Debug, PartialEq)]
-enum ParseState {
-    Empty,
-    Alpha,
-    AlphaDecimal,
-    Numeric,
-    NumericDecimal,
-}
-
-impl Tokenizer {
-    fn new(parse_string: String) -> Self {
-        Tokenizer {
-            token_stack: Vec::new(),
-            parse_string: parse_string.chars().rev().collect(),
-        }
-    }
-}
-
-impl Iterator for Tokenizer {
-    type Item = String;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        if !self.token_stack.is_empty() {
-            return Some(self.token_stack.pop().unwrap());
-        };
-        if self.parse_string.is_empty() {
-            return None;
-        };
-
-        let mut char_stack: Vec<char> = Vec::new();
-        let mut seen_letters = false;
-        let mut state = ParseState::Empty;
-
-        while let Some(next) = self.parse_string.pop() {
-            match state {
-                ParseState::Empty => {
-                    if next.is_numeric() {
-                        state = ParseState::Numeric;
-                        char_stack.push(next);
-                    } else if next.is_alphabetic() {
-                        state = ParseState::Alpha;
-                        seen_letters = true;
-                        char_stack.push(next);
-                    } else if next.is_whitespace() {
-                        char_stack.push(' ');
-                        break;
-                    } else {
-                        char_stack.push(next);
-                        break;
-                    }
-                }
-                ParseState::Alpha => {
-                    if next.is_alphabetic() {
-                        char_stack.push(next);
-                    } else if next == '.' {
-                        state = ParseState::AlphaDecimal;
-                        char_stack.push(next);
-                    } else {
-                        // We don't recognize the character, so push it back
-                        // to be handled later.
-                        self.parse_string.push(next);
-                        break;
-                    }
-                }
-                ParseState::AlphaDecimal => {
-                    if next == '.' || next.is_alphabetic() {
-                        char_stack.push(next);
-                    } else if next.is_numeric() && char_stack.last().unwrap().clone() == '.' {
-                        char_stack.push(next);
-                        state = ParseState::NumericDecimal;
-                    } else {
-                        self.parse_string.push(next);
-                        break;
-                    }
-                }
-                ParseState::Numeric => {
-                    if next.is_numeric() {
-                        char_stack.push(next);
-                    } else if next == '.' || (next == ',' && char_stack.len() >= 2) {
-                        char_stack.push(next);
-                        state = ParseState::NumericDecimal;
-                    } else {
-                        // We don't recognize the character, so push it back
-                        // to be handled later
-                        self.parse_string.push(next);
-                        break;
-                    }
-                }
-                ParseState::NumericDecimal => {
-                    if next == '.' || next.is_numeric() {
-                        char_stack.push(next);
-                    } else if next.is_alphabetic() && char_stack.last().unwrap().clone() == '.' {
-                        char_stack.push(next);
-                        state = ParseState::AlphaDecimal;
-                    } else {
-                        self.parse_string.push(next);
-                        break;
-                    }
-                }
-            }
-        }
-
-        // I like Python's version of this much better:
-        // needs_split = seen_letters or char_stack.count('.') > 1 or char_stack[-1] in '.,'
-        let dot_count = char_stack.iter().fold(0, |count, character| {
-            count + (if character == &'.' { 1 } else { 0 })
-        });
-        let needs_split = seen_letters || dot_count > 1 || char_stack.last().unwrap() == &'.'
-            || char_stack.last().unwrap() == &',';
-        let final_string: String = char_stack.into_iter().collect();
-
-        let mut tokens = match state {
-            ParseState::Empty => vec![final_string],
-            ParseState::Alpha => vec![final_string],
-            ParseState::Numeric => vec![final_string],
-            ParseState::AlphaDecimal => {
-                if needs_split {
-                    decimal_split(&final_string, false)
-                } else {
-                    vec![final_string]
-                }
-            }
-            ParseState::NumericDecimal => {
-                if needs_split {
-                    decimal_split(&final_string, dot_count == 0)
-                } else {
-                    vec![final_string]
-                }
-            }
-        }.into_iter()
-            .rev()
-            .collect();
-
-        self.token_stack.append(&mut tokens);
-        // UNWRAP: Previous match guaranteed that at least one token was added
-        let token = self.token_stack.pop().unwrap();
-        if state == ParseState::NumericDecimal && !token.contains(".") {
-            Some(token.replace(",", "."))
-        } else {
-            Some(token)
-        }
-    }
-}
-
-fn decimal_split(characters: &str, cast_period: bool) -> Vec<String> {
-    let mut token_stack: Vec<String> = Vec::new();
-    let mut char_stack: Vec<char> = Vec::new();
-    let mut state = ParseState::Empty;
-
-    for c in characters.chars() {
-        match state {
-            ParseState::Empty => {
-                if c.is_alphabetic() {
-                    char_stack.push(c);
-                    state = ParseState::Alpha;
-                } else if c.is_numeric() {
-                    char_stack.push(c);
-                    state = ParseState::Numeric;
-                } else {
-                    let character = if cast_period { '.' } else { c };
-                    token_stack.push(character.to_string());
-                }
-            }
-            ParseState::Alpha => {
-                if c.is_alphabetic() {
-                    char_stack.push(c);
-                } else {
-                    token_stack.push(char_stack.iter().collect());
-                    char_stack.clear();
-                    let character = if cast_period { '.' } else { c };
-                    token_stack.push(character.to_string());
-                    state = ParseState::Empty;
-                }
-            }
-            ParseState::Numeric => {
-                if c.is_numeric() {
-                    char_stack.push(c);
-                } else {
-                    token_stack.push(char_stack.iter().collect());
-                    char_stack.clear();
-                    let character = if cast_period { '.' } else { c };
-                    token_stack.push(character.to_string());
-                    state = ParseState::Empty;
-                }
-            }
-            _ => panic!("Invalid parse state during decimal_split()"),
-        }
-    }
-
-    match state {
-        ParseState::Alpha => token_stack.push(char_stack.iter().collect()),
-        ParseState::Numeric => token_stack.push(char_stack.iter().collect()),
-        ParseState::Empty => (),
-        _ => panic!("Invalid parse state during decimal_split()"),
-    }
-
-    token_stack
-}
-
 pub fn tokenize(parse_string: &str) -> Vec<String> {
     let tokenizer = Tokenizer::new(parse_string.to_owned());
     tokenizer.collect()
diff --git a/src/tokenize.rs b/src/tokenize.rs
new file mode 100644
index 0000000..2a44d25
--- /dev/null
+++ b/src/tokenize.rs
@@ -0,0 +1,203 @@
+pub(crate) struct Tokenizer {
+    token_stack: Vec<String>,
+    parse_string: String,
+}
+
+#[derive(Debug, PartialEq)]
+pub(crate) enum ParseState {
+    Empty,
+    Alpha,
+    AlphaDecimal,
+    Numeric,
+    NumericDecimal,
+}
+
+impl Tokenizer {
+    pub(crate) fn new(parse_string: String) -> Self {
+        Tokenizer {
+            token_stack: Vec::new(),
+            parse_string: parse_string.chars().rev().collect(),
+        }
+    }
+}
+
+impl Iterator for Tokenizer {
+    type Item = String;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if !self.token_stack.is_empty() {
+            return Some(self.token_stack.pop().unwrap());
+        };
+        if self.parse_string.is_empty() {
+            return None;
+        };
+
+        let mut char_stack: Vec<char> = Vec::new();
+        let mut seen_letters = false;
+        let mut state = ParseState::Empty;
+
+        while let Some(next) = self.parse_string.pop() {
+            match state {
+                ParseState::Empty => {
+                    if next.is_numeric() {
+                        state = ParseState::Numeric;
+                        char_stack.push(next);
+                    } else if next.is_alphabetic() {
+                        state = ParseState::Alpha;
+                        seen_letters = true;
+                        char_stack.push(next);
+                    } else if next.is_whitespace() {
+                        char_stack.push(' ');
+                        break;
+                    } else {
+                        char_stack.push(next);
+                        break;
+                    }
+                }
+                ParseState::Alpha => {
+                    if next.is_alphabetic() {
+                        char_stack.push(next);
+                    } else if next == '.' {
+                        state = ParseState::AlphaDecimal;
+                        char_stack.push(next);
+                    } else {
+                        // We don't recognize the character, so push it back
+                        // to be handled later.
+                        self.parse_string.push(next);
+                        break;
+                    }
+                }
+                ParseState::AlphaDecimal => {
+                    if next == '.' || next.is_alphabetic() {
+                        char_stack.push(next);
+                    } else if next.is_numeric() && char_stack.last().unwrap().clone() == '.' {
+                        char_stack.push(next);
+                        state = ParseState::NumericDecimal;
+                    } else {
+                        self.parse_string.push(next);
+                        break;
+                    }
+                }
+                ParseState::Numeric => {
+                    if next.is_numeric() {
+                        char_stack.push(next);
+                    } else if next == '.' || (next == ',' && char_stack.len() >= 2) {
+                        char_stack.push(next);
+                        state = ParseState::NumericDecimal;
+                    } else {
+                        // We don't recognize the character, so push it back
+                        // to be handled later
+                        self.parse_string.push(next);
+                        break;
+                    }
+                }
+                ParseState::NumericDecimal => {
+                    if next == '.' || next.is_numeric() {
+                        char_stack.push(next);
+                    } else if next.is_alphabetic() && char_stack.last().unwrap().clone() == '.' {
+                        char_stack.push(next);
+                        state = ParseState::AlphaDecimal;
+                    } else {
+                        self.parse_string.push(next);
+                        break;
+                    }
+                }
+            }
+        }
+
+        // I like Python's version of this much better:
+        // needs_split = seen_letters or char_stack.count('.') > 1 or char_stack[-1] in '.,'
+        let dot_count = char_stack.iter().fold(0, |count, character| {
+            count + (if character == &'.' { 1 } else { 0 })
+        });
+        let needs_split = seen_letters || dot_count > 1 || char_stack.last().unwrap() == &'.'
+            || char_stack.last().unwrap() == &',';
+        let final_string: String = char_stack.into_iter().collect();
+
+        let mut tokens = match state {
+            ParseState::Empty => vec![final_string],
+            ParseState::Alpha => vec![final_string],
+            ParseState::Numeric => vec![final_string],
+            ParseState::AlphaDecimal => {
+                if needs_split {
+                    decimal_split(&final_string, false)
+                } else {
+                    vec![final_string]
+                }
+            }
+            ParseState::NumericDecimal => {
+                if needs_split {
+                    decimal_split(&final_string, dot_count == 0)
+                } else {
+                    vec![final_string]
+                }
+            }
+        }.into_iter()
+            .rev()
+            .collect();
+
+        self.token_stack.append(&mut tokens);
+        // UNWRAP: Previous match guaranteed that at least one token was added
+        let token = self.token_stack.pop().unwrap();
+        if state == ParseState::NumericDecimal && !token.contains(".") {
+            Some(token.replace(",", "."))
+        } else {
+            Some(token)
+        }
+    }
+}
+
+fn decimal_split(characters: &str, cast_period: bool) -> Vec<String> {
+    let mut token_stack: Vec<String> = Vec::new();
+    let mut char_stack: Vec<char> = Vec::new();
+    let mut state = ParseState::Empty;
+
+    for c in characters.chars() {
+        match state {
+            ParseState::Empty => {
+                if c.is_alphabetic() {
+                    char_stack.push(c);
+                    state = ParseState::Alpha;
+                } else if c.is_numeric() {
+                    char_stack.push(c);
+                    state = ParseState::Numeric;
+                } else {
+                    let character = if cast_period { '.' } else { c };
+                    token_stack.push(character.to_string());
+                }
+            }
+            ParseState::Alpha => {
+                if c.is_alphabetic() {
+                    char_stack.push(c);
+                } else {
+                    token_stack.push(char_stack.iter().collect());
+                    char_stack.clear();
+                    let character = if cast_period { '.' } else { c };
+                    token_stack.push(character.to_string());
+                    state = ParseState::Empty;
+                }
+            }
+            ParseState::Numeric => {
+                if c.is_numeric() {
+                    char_stack.push(c);
+                } else {
+                    token_stack.push(char_stack.iter().collect());
+                    char_stack.clear();
+                    let character = if cast_period { '.' } else { c };
+                    token_stack.push(character.to_string());
+                    state = ParseState::Empty;
+                }
+            }
+            _ => panic!("Invalid parse state during decimal_split()"),
+        }
+    }
+
+    match state {
+        ParseState::Alpha => token_stack.push(char_stack.iter().collect()),
+        ParseState::Numeric => token_stack.push(char_stack.iter().collect()),
+        ParseState::Empty => (),
+        _ => panic!("Invalid parse state during decimal_split()"),
+    }
+
+    token_stack
+}