2c139bbf4e
This commit makes sure that the value zero is always encoded in an mpz_t as neg=0 and len=0 (previously it was just len=0). This invariant is needed for some of the bitwise operations that operate on negative numbers, because they cannot handle -0. For example (-((1<<100)-(1<<100)))|1 was being computed as -65535, instead of 1. Fixes issue #8042. Signed-off-by: Damien George <damien@micropython.org>
66 lines
1.8 KiB
Python
66 lines
1.8 KiB
Python
# test [0,1,-1] edge cases of bignum
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long_zero = (2**64) >> 65
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long_neg_zero = -long_zero
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long_one = long_zero + 1
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long_neg_one = -long_one
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cases = [long_zero, long_neg_zero, long_one, long_neg_one]
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print(cases)
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print([-c for c in cases])
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print([~c for c in cases])
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print([c >> 1 for c in cases])
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print([c << 1 for c in cases])
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# comparison of 0
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print(long_zero == 0)
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print(long_neg_zero == 0)
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print(long_one - 1 == 0)
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print(long_neg_one + 1 == 0)
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print(long_zero < 1)
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print(long_zero < -1)
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print(long_zero > 1)
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print(long_zero > -1)
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print(long_neg_zero < 1)
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print(long_neg_zero < -1)
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print(long_neg_zero > 1)
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print(long_neg_zero > -1)
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# generate zeros that involve negative numbers
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large = 1 << 70
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large_plus_one = large + 1
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zeros = (
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large - large,
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-large + large,
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large + -large,
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-(large - large),
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large - large_plus_one + 1,
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-large & (large - large),
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-large ^ -large,
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-large * (large - large),
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(large - large) // -large,
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-large // -large_plus_one,
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-(large + large) % large,
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(large + large) % -large,
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-(large + large) % -large,
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)
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print(zeros)
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# compute arithmetic operations that may have problems with -0
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# (this checks that -0 is never generated in the zeros tuple)
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cases = (0, 1, -1) + zeros
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for lhs in cases:
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print("-{} = {}".format(lhs, -lhs))
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print("~{} = {}".format(lhs, ~lhs))
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print("{} >> 1 = {}".format(lhs, lhs >> 1))
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print("{} << 1 = {}".format(lhs, lhs << 1))
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for rhs in cases:
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print("{} == {} = {}".format(lhs, rhs, lhs == rhs))
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print("{} + {} = {}".format(lhs, rhs, lhs + rhs))
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print("{} - {} = {}".format(lhs, rhs, lhs - rhs))
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print("{} * {} = {}".format(lhs, rhs, lhs * rhs))
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print("{} | {} = {}".format(lhs, rhs, lhs | rhs))
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print("{} & {} = {}".format(lhs, rhs, lhs & rhs))
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print("{} ^ {} = {}".format(lhs, rhs, lhs ^ rhs))
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