cython

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from libc.setjmp cimport *
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cdef void check_nonzero(jmp_buf ctx, int x) nogil:
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    if x == 0:
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        longjmp(ctx, 1)
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def nonzero(int x):
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    """
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    >>> nonzero(-1)
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    True
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    >>> nonzero(0)
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    False
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    >>> nonzero(1)
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    True
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    >>> nonzero(2)
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    True
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    """
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    cdef jmp_buf ctx
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    if setjmp(ctx) == 0:
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        check_nonzero(ctx, x)
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        return True
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    else:
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        return False
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from libc.string cimport strcpy
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cdef char[256] error_msg
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cdef jmp_buf error_ctx
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cdef void error(char msg[]) nogil:
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    strcpy(error_msg,msg)
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    longjmp(error_ctx, 1)
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cdef void c_call(int x) nogil:
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    if x<=0:
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        error(b"expected a positive value")
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def execute_c_call(int x):
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    """
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    >>> execute_c_call(+2)
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    >>> execute_c_call(+1)
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    >>> execute_c_call(+0)
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    Traceback (most recent call last):
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      ...
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    RuntimeError: expected a positive value
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    >>> execute_c_call(-1)
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    Traceback (most recent call last):
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      ...
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    RuntimeError: expected a positive value
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    """
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    if not setjmp(error_ctx):
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        c_call(x)
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    else:
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        raise RuntimeError(error_msg.decode())
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