Help/guide/tutorial/Step9/MathFunctions/mysqrt.cxx


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#include <iostream>

#include "MathFunctions.h"

// include the generated table
#include "Table.h"

// a hack square root calculation using simple operations
double mysqrt(double x)
{
  if (x <= 0) {
    return 0;
  }

  // use the table to help find an initial value
  double result = x;
  if (x >= 1 && x < 10) {
    std::cout << "Use the table to help find an initial value " << std::endl;
    result = sqrtTable[static_cast<int>(x)];
  }

  // do ten iterations
  for (int i = 0; i < 10; ++i) {
    if (result <= 0) {
      result = 0.1;
    }
    double delta = x - (result * result);
    result = result + 0.5 * delta / result;
    std::cout << "Computing sqrt of " << x << " to be " << result << std::endl;
  }

  return result;
}
"""Unit tests for the memoryview

XXX We need more tests! Some tests are in test_bytes
"""

import unittest
import test.support
import sys
import gc
import weakref
import array


class AbstractMemoryTests:
    source_bytes = b"abcdef"

    @property
    def _source(self):
        return self.source_bytes

    @property
    def _types(self):
        return filter(None, [self.ro_type, self.rw_type])

    def check_getitem_with_type(self, tp):
        item = self.getitem_type
        b = tp(self._source)
        oldrefcount = sys.getrefcount(b)
        m = self._view(b)
        self.assertEquals(m[0], item(b"a"))
        self.assertIsInstance(m[0], bytes)
        self.assertEquals(m[5], item(b"f"))
        self.assertEquals(m[-1], item(b"f"))
        self.assertEquals(m[-6], item(b"a"))
        # Bounds checking
        self.assertRaises(IndexError, lambda: m[6])
        self.assertRaises(IndexError, lambda: m[-7])
        self.assertRaises(IndexError, lambda: m[sys.maxsize])
        self.assertRaises(IndexError, lambda: m[-sys.maxsize])
        # Type checking
        self.assertRaises(TypeError, lambda: m[None])
        self.assertRaises(TypeError, lambda: m[0.0])
        self.assertRaises(TypeError, lambda: m["a"])
        m = None
        self.assertEquals(sys.getrefcount(b), oldrefcount)

    def test_getitem(self):
        for tp in self._types:
            self.check_getitem_with_type(tp)

    def test_iter(self):
        for tp in self._types:
            b = tp(self._source)
            m = self._view(b)
            self.assertEqual(list(m), [m[i] for i in range(len(m))])

    def test_setitem_readonly(self):
        if not self.ro_type:
            return
        b = self.ro_type(self._source)
        oldrefcount = sys.getrefcount(b)
        m = self._view(b)
        def setitem(value):
            m[0] = value
        self.assertRaises(TypeError, setitem, b"a")
        self.assertRaises(TypeError, setitem, 65)
        self.assertRaises(TypeError, setitem, memoryview(b"a"))
        m = None
        self.assertEquals(sys.getrefcount(b), oldrefcount)

    def test_setitem_writable(self):
        if not self.rw_type:
            return
        tp = self.rw_type
        b = self.rw_type(self._source)
        oldrefcount = sys.getrefcount(b)
        m = self._view(b)
        m[0] = tp(b"0")
        self._check_contents(tp, b, b"0bcdef")
        m[1:3] = tp(b"12")
        self._check_contents(tp, b, b"012def")
        m[1:1] = tp(b"")
        self._check_contents(tp, b, b"012def")
        m[:] = tp(b"abcdef")
        self._check_contents(tp, b, b"abcdef")

        # Overlapping copies of a view into itself
        m[0:3] = m[2:5]
        self._check_contents(tp, b, b"cdedef")
        m[:] = tp(b"abcdef")
        m[2:5] = m[0:3]
        self._check_contents(tp, b, b"ababcf")

        def setitem(key, value):
            m[key] = tp(value)
        # Bounds checking
        self.assertRaises(IndexError, setitem, 6, b"a")
        self.assertRaises(IndexError, setitem, -7, b"a")
        self.assertRaises(IndexError, setitem, sys.maxsize, b"a")
        self.assertRaises(IndexError, setitem, -sys.maxsize, b"a")
        # Wrong index/slice types
        self.assertRaises(TypeError, setitem, 0.0, b"a")
        self.assertRaises(TypeError, setitem, (0,), b"a")
        self.assertRaises(TypeError, setitem, "a", b"a")
        # Trying to resize the memory object
        self.assertRaises(ValueError, setitem, 0, b"")
        self.assertRaises(ValueError, setitem, 0, b"ab")
        self.assertRaises(ValueError, setitem, slice(1,1), b"a")
        self.assertRaises(ValueError, setitem, slice(0,2), b"a")

        m = None
        self.assertEquals(sys.getrefcount(b), oldrefcount)

    def test_tobytes(self):
        for tp in self._types:
            m = self._view(tp(self._source))
            b = m.tobytes()
            # This calls self.getitem_type() on each separate byte of b"abcdef"
            expected = b"".join(
                self.getitem_type(bytes([c])) for c in b"abcdef")
            self.assertEquals(b, expected)
            self.assertIsInstance(b, bytes)

    def test_tolist(self):
        for tp in self._types:
            m = self._view(tp(self._source))
            l = m.tolist()
            self.assertEquals(l, list(b"abcdef"))

    def test_compare(self):
        # memoryviews can compare for equality with other objects
        # having the buffer interface.
        for tp in self._types:
            m = self._view(tp(self._source))
            for tp_comp in self._types:
                self.assertTrue(m == tp_comp(b"abcdef"))
                self.assertFalse(m != tp_comp(b"abcdef"))
                self.assertFalse(m == tp_comp(b"abcde"))
                self.assertTrue(m != tp_comp(b"abcde"))
                self.assertFalse(m == tp_comp(b"abcde1"))
                self.assertTrue(m != tp_comp(b"abcde1"))
            self.assertTrue(m == m)
            self.assertTrue(m == m[:])
            self.assertTrue(m[0:6] == m[:])
            self.assertFalse(m[0:5] == m)

            # Comparison with objects which don't support the buffer API
            self.assertFalse(m == "abcdef")
            self.assertTrue(m != "abcdef")
            self.assertFalse("abcdef" == m)
            self.assertTrue("abcdef" != m)

            # Unordered comparisons
            for c in (m, b"abcdef"):
                self.assertRaises(TypeError, lambda: m < c)
                self.assertRaises(TypeError, lambda: c <= m)
                self.assertRaises(TypeError, lambda: m >= c)
                self.assertRaises(TypeError, lambda: c > m)

    def check_attributes_with_type(self, tp):
        m = self._view(tp(self._source))
        self.assertEquals(m.format, self.format)
        self.assertEquals(m.itemsize, self.itemsize)
        self.assertEquals(m.ndim, 1)
        self.assertEquals(m.shape, (6,))
        self.assertEquals(len(m), 6)
        self.assertEquals(m.strides, (self.itemsize,))
        self.assertEquals(m.suboffsets, None)
        return m

    def test_attributes_readonly(self):
        if not self.ro_type:
            return
        m = self.check_attributes_with_type(self.ro_type)
        self.assertEquals(m.readonly, True)

    def test_attributes_writable(self):
        if not self.rw_type:
            return
        m = self.check_attributes_with_type(self.rw_type)
        self.assertEquals(m.readonly, False)

    def test_getbuffer(self):
        # Test PyObject_GetBuffer() on a memoryview object.
        for tp in self._types:
            b = tp(self._source)
            oldrefcount = sys.getrefcount(b)
            m = self._view(b)
            oldviewrefcount = sys.getrefcount(m)
            s = str(m, "utf-8")
            self._check_contents(tp, b, s.encode("utf-8"))
            self.assertEquals(sys.getrefcount(m), oldviewrefcount)
            m = None
            self.assertEquals(sys.getrefcount(b), oldrefcount)

    def test_gc(self):
        for tp in self._types:
            if not isinstance(tp, type):
                # If tp is a factory rather than a plain type, skip
                continue

            class MySource(tp):
                pass
            class MyObject:
                pass

            # Create a reference cycle through a memoryview object
            b = MySource(tp(b'abc'))
            m = self._view(b)
            o = MyObject()
            b.m = m
            b.o = o
            wr = weakref.ref(o)
            b = m = o = None
            # The cycle must be broken
            gc.collect()
            self.assertTrue(wr() is None, wr())


# Variations on source objects for the buffer: bytes-like objects, then arrays
# with itemsize > 1.
# NOTE: support for multi-dimensional objects is unimplemented.

class BaseBytesMemoryTests(AbstractMemoryTests):
    ro_type = bytes
    rw_type = bytearray
    getitem_type = bytes
    itemsize = 1
    format = 'B'

class BaseArrayMemoryTests(AbstractMemoryTests):
    ro_type = None
    rw_type = lambda self, b: array.array('i', list(b))
    getitem_type = lambda self, b: array.array('i', list(b)).tostring()
    itemsize = array.array('i').itemsize
    format = 'i'

    def test_getbuffer(self):
        # XXX Test should be adapted for non-byte buffers
        pass

    def test_tolist(self):
        # XXX NotImplementedError: tolist() only supports byte views
        pass


# Variations on indirection levels: memoryview, slice of memoryview,
# slice of slice of memoryview.
# This is important to test allocation subtleties.

class BaseMemoryviewTests:
    def _view(self, obj):
        return memoryview(obj)

    def _check_contents(self, tp, obj, contents):
        self.assertEquals(obj, tp(contents))

class BaseMemorySliceTests:
    source_bytes = b"XabcdefY"

    def _view(self, obj):
        m = memoryview(obj)
        return m[1:7]

    def _check_contents(self, tp, obj, contents):
        self.assertEquals(obj[1:7], tp(contents))

    def test_refs(self):
        for tp in self._types:
            m = memoryview(tp(self._source))
            oldrefcount = sys.getrefcount(m)
            m[1:2]
            self.assertEquals(sys.getrefcount(m), oldrefcount)

class BaseMemorySliceSliceTests:
    source_bytes = b"XabcdefY"

    def _view(self, obj):
        m = memoryview(obj)
        return m[:7][1:]

    def _check_contents(self, tp, obj, contents):
        self.assertEquals(obj[1:7], tp(contents))


# Concrete test classes

class BytesMemoryviewTest(unittest.TestCase,
    BaseMemoryviewTests, BaseBytesMemoryTests):

    def test_constructor(self):
        for tp in self._types:
            ob = tp(self._source)
            self.assertTrue(memoryview(ob))
            self.assertTrue(memoryview(object=ob))
            self.assertRaises(TypeError, memoryview)
            self.assertRaises(TypeError, memoryview, ob, ob)
            self.assertRaises(TypeError, memoryview, argument=ob)
            self.assertRaises(TypeError, memoryview, ob, argument=True)

class ArrayMemoryviewTest(unittest.TestCase,
    BaseMemoryviewTests, BaseArrayMemoryTests):

    def test_array_assign(self):
        # Issue #4569: segfault when mutating a memoryview with itemsize != 1
        a = array.array('i', range(10))
        m = memoryview(a)
        new_a = array.array('i', range(9, -1, -1))
        m[:] = new_a
        self.assertEquals(a, new_a)


class BytesMemorySliceTest(unittest.TestCase,
    BaseMemorySliceTests, BaseBytesMemoryTests):
    pass

class ArrayMemorySliceTest(unittest.TestCase,
    BaseMemorySliceTests, BaseArrayMemoryTests):
    pass

class BytesMemorySliceSliceTest(unittest.TestCase,
    BaseMemorySliceSliceTests, BaseBytesMemoryTests):
    pass

class ArrayMemorySliceSliceTest(unittest.TestCase,
    BaseMemorySliceSliceTests, BaseArrayMemoryTests):
    pass


def test_main():
    test.support.run_unittest(__name__)

if __name__ == "__main__":
    test_main()