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[jsbuilt-ins] fixing numerical stability of to_string

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This commit is contained in:
sulyi 2017-01-30 05:38:55 +01:00
parent 56cecddc75
commit 9ead39caee
1 changed files with 5 additions and 6 deletions
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11
youtube_dl/jsinterp/jsbuilt_ins.py
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@ -90,21 +90,20 @@ def to_string(o):
elif isinf(ov): elif isinf(ov):
return 'Infinity' return 'Infinity'
else: else:
n = log10(ov) # numerically unstable example: 3333330000000000000.3 or 3.3333300000000000003e+20
c = 1 if 0 < n else 0 n = log10(ov) + 1
n = int(n) n = int(n)
k = 1 k = 1
while True: while True:
exp = 10 ** (n - k) exp = 10 ** (k - n)
s = int(ov / exp) s = int(ov * exp)
if abs(ov - s * exp) < float_info.epsilon: if abs(ov * exp - s) < float_info.epsilon:
break break
k += 1 k += 1
if s % 10 == 0: if s % 10 == 0:
s //= 10 s //= 10
n += c
m = '%d' % s m = '%d' % s
if k <= n <= 21: if k <= n <= 21: