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| author | gfyoung <gfyoung17@gmail.com> | 2017-02-22 20:44:38 -0500 |
|---|---|---|
| committer | Charles Harris <charlesr.harris@gmail.com> | 2017-03-04 10:49:39 -0700 |
| commit | 235632b4d01163e1b6ff01ab65ba3488068fcd5f (patch) | |
| tree | f6e0012129ce9c5f8f7afbc04636587807712a4d | |
| parent | 542390d680d5779af1028591d1885af0ff6d25ed (diff) | |
| download | numpy-235632b4d01163e1b6ff01ab65ba3488068fcd5f.tar.gz | |
BUG: Remove extra digit in binary_repr at limit
For negative numbers at the limit for a given
number of digits, we were appending an extra
digit unnecessarily.
Closes gh-8670.
| -rw-r--r-- | numpy/core/numeric.py | 10 | ||||
| -rw-r--r-- | numpy/core/tests/test_numeric.py | 12 |
2 files changed, 20 insertions, 2 deletions
diff --git a/numpy/core/numeric.py b/numpy/core/numeric.py index b90b0a9c9..5a8b92a4f 100644 --- a/numpy/core/numeric.py +++ b/numpy/core/numeric.py @@ -2212,7 +2212,7 @@ def binary_repr(num, width=None): designated form. If the `width` value is insufficient, it will be ignored, and `num` will - be returned in binary(`num` > 0) or two's complement (`num` < 0) form + be returned in binary (`num` > 0) or two's complement (`num` < 0) form with its width equal to the minimum number of bits needed to represent the number in the designated form. This behavior is deprecated and will later raise an error. @@ -2282,10 +2282,16 @@ def binary_repr(num, width=None): else: poswidth = len(bin(-num)[2:]) - twocomp = 2**(poswidth + 1) + num + # See gh-8679: remove extra digit + # for numbers at boundaries. + if 2**(poswidth - 1) == -num: + poswidth -= 1 + + twocomp = 2**(poswidth + 1) + num binary = bin(twocomp)[2:] binwidth = len(binary) + outwidth = max(binwidth, width) warn_if_insufficient(width, binwidth) return '1' * (outwidth - binwidth) + binary diff --git a/numpy/core/tests/test_numeric.py b/numpy/core/tests/test_numeric.py index c31e9e07c..28b58e358 100644 --- a/numpy/core/tests/test_numeric.py +++ b/numpy/core/tests/test_numeric.py @@ -1149,6 +1149,18 @@ class TestBinaryRepr(TestCase): assert_equal(np.binary_repr(10, width=7), '0001010') assert_equal(np.binary_repr(-5, width=7), '1111011') + def test_neg_width_boundaries(self): + # see gh-8670 + + # Ensure that the example in the issue does not + # break before proceeding to a more thorough test. + assert_equal(np.binary_repr(-128, width=8), '10000000') + + for width in range(1, 11): + num = -2**(width - 1) + exp = '1' + (width - 1) * '0' + assert_equal(np.binary_repr(num, width=width), exp) + class TestBaseRepr(TestCase): def test_base3(self): |