Add __call__

Author: yalishanda42

README.md

@@ -55,6 +55,9 @@ Polynomial(12, 6, 2)
 ``` pycon
 >>> (a + b).calculate(5)
 780
+
+>>> а(2)  #  equivalent to a.calculate(2)
+26
 ```
 
 ### Multiplication

polynomial/core.py

@@ -291,6 +291,10 @@ def calculate(self, x):
 
         return sum(ak * (x ** k) for ak, k in self.terms)
 
+    def __call__(self, x):
+        """Calculate the value of the polynomial at a given point."""
+        return self.calculate(x)
+
     def __getattr__(self, name):
         """Get coefficient by letter name: ax^n + bx^{n-1} + ... + yx + z."""
         if len(name) != 1:

tests/test_polynomials_operations.py

@@ -1310,6 +1310,23 @@ def test_calculate_zero_polynomial(self):
         self.assertEqual(0, Constant(0).calculate(5))
         self.assertEqual(0, Monomial(0, 1).calculate(1.1))
 
+    def test_call(self):
+        """Tests calculate on a simple polynomial."""
+        a = Polynomial(1, 2, 3)
+
+        def eqn(x):
+            return x ** 2 + 2 * x + 3
+
+        for i in range(-100, 100):
+            i = i / 100
+            self.assertEqual(eqn(i), a(i))
+
+    def test_call_zero_polynomial(self):
+        """Test that calculations of zero polynomial values always give 0."""
+        self.assertEqual(0, ZeroPolynomial()(1))
+        self.assertEqual(0, Constant(0)(5))
+        self.assertEqual(0, Monomial(0, 1)(1.1))
+
     def test_setattr_raises_error(self):
         """Test that setting invalid terms raises an error."""
         invalid_setattrs = [