Fixed bug: PR_CLOSE after group expression

Author: TheWeirdDev

source/calcool/expression.d

@@ -26,6 +26,7 @@ private:
         static foreach (i; trigonometry ~ other) {
             funcs[i] = mixin("&" ~ i);
         }
+        funcs["abs"] = &abs!real;
     }
 
 public:

source/calcool/parser.d

@@ -64,6 +64,10 @@ public:
     Expression parseGroupExpression() {
         auto inside = parseExpression(Precedence.START);
         expect(TokenType.PR_CLOSE);
+        if (input.length > 0 && input.front().type == TokenType.PR_CLOSE) {
+            input.length = 0;
+            throw new ParseException("Syntax error");
+        }
         return inside;
     }