diff --git a/src/lexer.rs b/src/lexer.rs
index 6d852f2..553c221 100644
--- a/src/lexer.rs
+++ b/src/lexer.rs
@@ -42,14 +42,14 @@ pub enum Symbol {
 }
 
 impl Lexer {
-    pub fn new(input: String) -> Lexer {
+    pub fn new(input: &str) -> Lexer {
         Lexer {
             input: input.chars().collect(),
             pos: 0,
         }
     }
 
-    pub fn next(&mut self) -> Result<Option<Token>, Error> {
+    pub fn lex_any(&mut self) -> Result<Option<Token>, Error> {
         let Some(&ch) = self.input.get(self.pos) else {
             return Ok(None);
         };
@@ -95,7 +95,7 @@ impl Lexer {
             },
             ch if ch.is_whitespace() => {
                 self.pos += 1;
-                return self.next();
+                return self.lex_any();
             }
             _ => self.lex_op()?,
         };
@@ -345,3 +345,11 @@ impl Lexer {
         Ok(Token::Symbol(symbol))
     }
 }
+
+impl Iterator for Lexer {
+    type Item = Result<Token, Error>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.lex_any().transpose()
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..83c38aa
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,10 @@
+#![allow(dead_code, clippy::single_match, clippy::only_used_in_recursion)]
+
+pub mod data;
+pub mod error;
+pub mod generator;
+pub mod lexer;
+pub mod parser;
+pub mod types;
+
+pub use error::Error;
diff --git a/src/main.rs b/src/main.rs
index 2237473..f65aef4 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,33 +4,20 @@ a second time when generating (so the types are known), there should be
 a better way
 */
 
-#![allow(dead_code, clippy::single_match, clippy::only_used_in_recursion)]
-
-mod data;
-mod error;
-mod generator;
-mod lexer;
-mod parser;
-mod types;
-
-pub use error::Error;
+use lang::{generator, lexer, parser};
 use generator::Generator;
 
 fn main() {
     let source = std::fs::read_to_string(std::env::args().skip(1).next().expect("no filename!")).expect("no source!");
-    let mut lexer = lexer::Lexer::new(source);
+    let lexer = lexer::Lexer::new(&source);
 
-    let mut tokens = vec![];
-    loop {
-        match lexer.next() {
-            Ok(None) => break,
-            Ok(Some(token)) => tokens.push(token),
-            Err(error) => {
-                eprintln!("error: {:?}", error);
-                return;
-            }
+    let tokens = match lexer.collect::<Result<Vec<_>, _>>() {
+        Ok(tokens) => tokens,
+        Err(error) => {
+            eprintln!("error: {:?}", error);
+            return;
         }
-    }
+    };
     
     // dbg!(&tokens);
     
diff --git a/tests/lexer.rs b/tests/lexer.rs
new file mode 100644
index 0000000..de8a531
--- /dev/null
+++ b/tests/lexer.rs
@@ -0,0 +1,14 @@
+use lang::{lexer::{Lexer, Token, Symbol}, Error};
+
+#[test]
+fn test_foo() {
+    let tokens: Result<Vec<_>, Error> = Lexer::new("1 * 5 / 3").collect();
+    let tokens = tokens.expect("should parse");
+    assert_eq!(tokens, vec![
+        Token::Number { radix: 10, text: "1".into() },
+        Token::Symbol(Symbol::Star),
+        Token::Number { radix: 10, text: "5".into() },
+        Token::Symbol(Symbol::Slash),
+        Token::Number { radix: 10, text: "3".into() },
+    ])
+}