add python bindings for floor_log2 and ceil_log2

Author: programmerjake

src/python.rs

@@ -93,6 +93,20 @@ impl RealAlgebraicNumberPy {
             })
             .ok_or_else(get_div_by_zero_error)
     }
+    /// returns `floor(log2(self))`
+    fn floor_log2(&self) -> PyResult<i64> {
+        Python::acquire_gil()
+            .python()
+            .allow_threads(|| self.value.checked_floor_log2())
+            .ok_or_else(get_floor_ceil_log2_error)
+    }
+    /// returns `ceil(log2(self))`
+    fn ceil_log2(&self) -> PyResult<i64> {
+        Python::acquire_gil()
+            .python()
+            .allow_threads(|| self.value.checked_ceil_log2())
+            .ok_or_else(get_floor_ceil_log2_error)
+    }
 }
 
 #[pyproto]
@@ -118,6 +132,10 @@ fn get_div_by_zero_error() -> PyErr {
     ZeroDivisionError::py_err("can't divide RealAlgebraicNumber by zero")
 }
 
+fn get_floor_ceil_log2_error() -> PyErr {
+    ValueError::py_err("can't extract base-2 logarithm of zero or negative RealAlgebraicNumber")
+}
+
 #[pyproto]
 impl PyNumberProtocol for RealAlgebraicNumberPy {
     fn __add__(lhs: &PyAny, rhs: RealAlgebraicNumberPy) -> PyResult<RealAlgebraicNumberPy> {

tests/test_real_algebraic_number.py

@@ -227,6 +227,28 @@ def test_abs(self):
         self.assertEqual(abs(RealAlgebraicNumber(1)), 1)
         self.assertEqual(abs(RealAlgebraicNumber(-2)), 2)
 
+    def test_floor_ceil_log2(self):
+        with self.assertRaises(ValueError):
+            RealAlgebraicNumber(0).floor_log2()
+        with self.assertRaises(ValueError):
+            RealAlgebraicNumber(0).ceil_log2()
+        with self.assertRaises(ValueError):
+            RealAlgebraicNumber(-1).floor_log2()
+        with self.assertRaises(ValueError):
+            RealAlgebraicNumber(-1).ceil_log2()
+        self.assertEqual(RealAlgebraicNumber(1).floor_log2(), 0)
+        self.assertEqual(RealAlgebraicNumber(1).ceil_log2(), 0)
+        self.assertEqual(RealAlgebraicNumber(2).floor_log2(), 1)
+        self.assertEqual(RealAlgebraicNumber(2).ceil_log2(), 1)
+        self.assertEqual(RealAlgebraicNumber(3).floor_log2(), 1)
+        self.assertEqual(RealAlgebraicNumber(3).ceil_log2(), 2)
+        self.assertEqual(RealAlgebraicNumber(4).floor_log2(), 2)
+        self.assertEqual(RealAlgebraicNumber(4).ceil_log2(), 2)
+        self.assertEqual((RealAlgebraicNumber(1) / 4).floor_log2(), -2)
+        self.assertEqual((RealAlgebraicNumber(1) / 4).ceil_log2(), -2)
+        self.assertEqual((RealAlgebraicNumber(1) / 3).floor_log2(), -2)
+        self.assertEqual((RealAlgebraicNumber(1) / 3).ceil_log2(), -1)
+
 
 if __name__ == '__main__':
     unittest.main()