diff --git a/src/lexer/char.rs b/src/lexer/char.rs
index 3155fca..f5ab38f 100644
--- a/src/lexer/char.rs
+++ b/src/lexer/char.rs
@@ -15,7 +15,6 @@ pub trait Lexable {
 
     fn is_identifier_initial(&self) -> bool;
     fn is_identifier_subsequent(&self) -> bool;
-    fn is_identifier_single(&self) -> bool;
     fn is_identifier_delimiter(&self) -> bool;
 
     fn is_boolean_true(&self) -> bool;
@@ -73,10 +72,6 @@ impl Lexable for char {
         charset::identifier_subsequents().contains(&self)
     }
 
-    fn is_identifier_single(&self) -> bool {
-        charset::identifier_singles().contains(&self)
-    }
-
     fn is_identifier_delimiter(&self) -> bool {
         self.is_whitespace()
             || self.is_comment_initial()
diff --git a/src/lexer/charset.rs b/src/lexer/charset.rs
index eb7e7cb..63aaaaf 100644
--- a/src/lexer/charset.rs
+++ b/src/lexer/charset.rs
@@ -41,7 +41,3 @@ pub fn identifier_subsequents() -> CharSet {
     subsequents.extend(extras.iter());
     subsequents
 }
-
-pub fn identifier_singles() -> CharSet {
-    CharSet::from_iter("+-".chars())
-}
diff --git a/src/lexer/mod.rs b/src/lexer/mod.rs
index 86507ca..7fa667f 100644
--- a/src/lexer/mod.rs
+++ b/src/lexer/mod.rs
@@ -11,6 +11,7 @@ mod str;
 use self::char::Lexable;
 use self::number::NumberBuilder;
 use self::number::Radix;
+use self::number::Sign;
 use self::str::CharAt;
 use self::str::RelativeIndexable;
 use self::token::Lex;
@@ -110,7 +111,7 @@ impl Lexer {
             self.advance();
         }
 
-        else if c.is_identifier_single() {
+        else if let Some(sign) = Sign::from_char(c) {
             *token = Some(Token::Identifier(c.to_string()));
         }
         else if c.is_identifier_initial() {