added test for decision to calculate string with calculate_string as well as corresponding functionality

src/main/py/read_math_function.py

@@ -1,6 +1,10 @@
 def read_constant(type, value):
     if type != "c":
         return False
+    if is_string(value):
+        if is_allowed_string(type, value):
+            constant = calculate_string(value)
+            return constant
     return value
 
 

src/test/py/test_read_math_function.py

@@ -19,6 +19,8 @@ class read_function(unittest.TestCase):
         self.assertEqual(calculate_string("42+1-3*4/3"), 39)
     def test_constant_calculate_with_pow(self):
         self.assertEqual(calculate_string("42^(2)+1-3*4/3"), 1761)
+    def test_constant_calculate_string_decision(self):
+        self.assertEqual(read_constant("c", "42^(2)+1-3*4/3"), 1761)
 
 if __name__ == '__main__':
     unittest.main()