Add single character identifiers

src/lexer/char.rs

@@ -9,15 +9,16 @@ pub trait Lexable {
     fn is_right_paren(&self) -> bool;
     fn is_identifier_initial(&self) -> bool;
     fn is_identifier_subsequent(&self) -> bool;
+    fn is_identifier_single(&self) -> bool;
 }
 
 impl Lexable for char {
     fn is_left_paren(&self) -> bool {
-        self == &'('
+        *self == '('
     }
 
     fn is_right_paren(&self) -> bool {
-        self == &')'
+        *self == ')'
     }
 
     fn is_identifier_initial(&self) -> bool {
@@ -27,5 +28,9 @@ impl Lexable for char {
     fn is_identifier_subsequent(&self) -> bool {
         charset::identifier_subsequents().contains(&self)
     }
+
+    fn is_identifier_single(&self) -> bool {
+        charset::identifier_singles().contains(&self)
+    }
 }