From 1e162d3753528ef25885f20106512599ebad9b0b Mon Sep 17 00:00:00 2001 From: Guido van Rossum Date: Sat, 9 May 1998 14:42:25 +0000 Subject: 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. --- Python/bltinmodule.c | 18 +++++++++++++----- 1 file 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 * -- cgit v0.12