[lexer] Add number::Sign state

lexer/src/error.rs

@@ -18,5 +18,9 @@ impl Error {
         Error::new(format!("invalid character: {}", c))
     }
 
+    pub fn unexpected_eof() -> Error {
+        Error::new("unexpected EOF".to_string())
+    }
+
     pub fn msg(&self) -> &str { &self.message }
 }

lexer/src/states/number/prefix.rs

@@ -2,10 +2,11 @@
  * Eryn Wells <eryn@erynwells.me>
  */
 
+use chars::Lexable;
 use error::Error;
 use states::{State, StateResult};
-use states::number::{Radix, Exact};
-use states::number::Builder;
+use states::number::{Builder, Radix, Exact};
+use states::number::sign::Sign;
 use token::Token;
 
 #[derive(Debug)] pub struct Prefix(Builder);
@@ -31,9 +32,12 @@ impl Prefix {
 
 impl State for Prefix {
     fn lex(&mut self, c: char) -> StateResult {
-        match c {
-            '#' => StateResult::advance(Box::new(Hash(self.0))),
-            _ => StateResult::fail(Error::invalid_char(c))
+        if c.is_hash() {
+            StateResult::advance(Box::new(Hash(self.0)))
+        } else if let Some(sn) = Sign::with_char(self.0, c) {
+            StateResult::advance(Box::new(sn))
+        } else {
+            StateResult::fail(Error::invalid_char(c))
         }
     }
 

lexer/src/states/number/sign.rs

@@ -0,0 +1,47 @@
+/* lexer/src/states/number/sign.rs
+ * Eryn Wells <eryn@erynwells.me>
+ */
+
+use error::Error;
+use states::{State, StateResult};
+use states::number::Builder;
+use states::number::Sign as Sgn;
+use token::Token;
+
+#[derive(Debug)] pub struct Sign(Builder);
+
+impl Sign {
+    pub fn new(b: Builder) -> Sign {
+        Sign(b)
+    }
+
+    pub fn with_char(b: Builder, c: char) -> Option<Sign> {
+        if !b.seen_sign() {
+            match c {
+                '+' => {
+                    let mut b = b.clone();
+                    b.push_sign(Sgn::Pos);
+                    Some(Sign::new(b))
+                },
+                '-' => {
+                    let mut b = b.clone();
+                    b.push_sign(Sgn::Neg);
+                    Some(Sign::new(b))
+                },
+                _ => None
+            }
+        } else {
+            None
+        }
+    }
+}
+
+impl State for Sign {
+    fn lex(&mut self, c: char) -> StateResult {
+        StateResult::fail(Error::invalid_char(c))
+    }
+
+    fn none(&mut self) -> Result<Option<Token>, Error> {
+        Err(Error::unexpected_eof())
+    }
+}