Add char::is_eof()

src/lexer/char.rs

@@ -14,6 +14,7 @@ pub trait Lexable {
     fn is_boolean_true(&self) -> bool;
     fn is_boolean_false(&self) -> bool;
     fn is_newline(&self) -> bool;
+    fn is_eof(&self) -> bool;
     fn is_comment_initial(&self) -> bool;
 }
 
@@ -54,6 +55,10 @@ impl Lexable for char {
         *self == '\n'
     }
 
+    fn is_eof(&self) -> bool {
+        *self == '\0'
+    }
+
     fn is_comment_initial(&self) -> bool {
         *self == ';'
     }