cython

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from libc.stdlib cimport malloc, free
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from cpython.object cimport Py_EQ, Py_NE
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def double_ptr_slice(x, L, int a, int b):
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    """
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    >>> L = list(range(10))
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    >>> double_ptr_slice(5, L, 0, 10)
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    >>> double_ptr_slice(6, L, 0, 10)
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    >>> double_ptr_slice(None, L, 0, 10)
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    >>> double_ptr_slice(0, L, 3, 7)
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    >>> double_ptr_slice(5, L, 3, 7)
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    >>> double_ptr_slice(9, L, 3, 7)
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    >>> double_ptr_slice(EqualsEvens(), L, 0, 10)
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    >>> double_ptr_slice(EqualsEvens(), L, 1, 10)
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    """
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    cdef double *L_c = NULL
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    try:
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        L_c = <double*>malloc(<unsigned long> len(L) * sizeof(double))
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        for i, a in enumerate(L):
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            L_c[i] = L[i]
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        assert (x in L_c[:b]) == (x in L[:b])
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        assert (x not in L_c[:b]) == (x not in L[:b])
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        assert (x in L_c[a:b]) == (x in L[a:b])
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        assert (x not in L_c[a:b]) == (x not in L[a:b])
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        assert (x in L_c[a:b:2]) == (x in L[a:b:2])
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        assert (x not in L_c[a:b:2]) == (x not in L[a:b:2])
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    finally:
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        free(L_c)
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def void_ptr_slice(py_x, L, int a, int b):
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    """
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    >>> L = list(range(10))
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    >>> void_ptr_slice(5, L, 0, 10)
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    >>> void_ptr_slice(6, L, 0, 10)
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    >>> void_ptr_slice(None, L, 0, 10)
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    >>> void_ptr_slice(0, L, 3, 7)
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    >>> void_ptr_slice(5, L, 3, 7)
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    >>> void_ptr_slice(9, L, 3, 7)
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    """
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    # I'm using the fact that small Python ints are cached.
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    cdef void **L_c = NULL
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    cdef void *x = <void*>py_x
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    try:
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        L_c = <void**>malloc(<unsigned long> len(L) * sizeof(void*))
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        for i, a in enumerate(L):
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            L_c[i] = <void*>L[i]
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        assert (x in L_c[:b]) == (py_x in L[:b])
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        assert (x not in L_c[:b]) == (py_x not in L[:b])
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        assert (x in L_c[a:b]) == (py_x in L[a:b])
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        assert (x not in L_c[a:b]) == (py_x not in L[a:b])
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        assert (x in L_c[a:b:2]) == (py_x in L[a:b:2])
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        assert (x not in L_c[a:b:2]) == (py_x not in L[a:b:2])
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    finally:
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        free(L_c)
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cdef class EqualsEvens:
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    """
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    >>> e = EqualsEvens()
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    >>> e == 2
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    True
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    >>> e == 5
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    False
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    >>> [e == k for k in range(4)]
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    [True, False, True, False]
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    """
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    def __richcmp__(self, other, int op):
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        if op == Py_EQ:
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            return other % 2 == 0
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        elif op == Py_NE:
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            return other % 2 == 1
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        else:
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            return False
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