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| author | Guido van Rossum <guido@python.org> | 1998-05-09 14:42:25 (GMT) |
|---|---|---|
| committer | Guido van Rossum <guido@python.org> | 1998-05-09 14:42:25 (GMT) |
| commit | 1e162d3753528ef25885f20106512599ebad9b0b (patch) | |
| tree | bb88757effc3aba352db9f956a09a4cda8b48812 | |
| parent | ae94cf292ba0317ac70a5eca3004a2fa5bcaad80 (diff) | |
| download | cpython-1e162d3753528ef25885f20106512599ebad9b0b.zip cpython-1e162d3753528ef25885f20106512599ebad9b0b.tar.gz cpython-1e162d3753528ef25885f20106512599ebad9b0b.tar.bz2 | |
Implement round() slightly different, so that for negative ndigits no
additional errors happen in the last step. The trick is to avoid
division by 0.1**n -- multiply by 10.0**n instead.
| -rw-r--r-- | Python/bltinmodule.c | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c index fd31405..68a5109 100644 --- a/Python/bltinmodule.c +++ b/Python/bltinmodule.c @@ -1488,14 +1488,22 @@ builtin_round(self, args) if (!PyArg_ParseTuple(args, "d|i:round", &x, &ndigits)) return NULL; f = 1.0; - for (i = ndigits; --i >= 0; ) + i = abs(ndigits); + while (--i >= 0) f = f*10.0; - for (i = ndigits; ++i <= 0; ) - f = f*0.1; + if (ndigits < 0) + x /= f; + else + x *= f; if (x >= 0.0) - return PyFloat_FromDouble(floor(x*f + 0.5) / f); + x = floor(x + 0.5); + else + x = ceil(x - 0.5); + if (ndigits < 0) + x *= f; else - return PyFloat_FromDouble(ceil(x*f - 0.5) / f); + x /= f; + return PyFloat_FromDouble(x); } static PyObject * |