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Implement round() slightly different, so that for negative ndigits no

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additional errors happen in the last step.  The trick is to avoid
division by 0.1**n -- multiply by 10.0**n instead.
This commit is contained in:
Guido van Rossum 1998-05-09 14:42:25 +00:00
parent ae94cf292b
commit 1e162d3753
1 changed files with 14 additions and 6 deletions
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20
Python/bltinmodule.c
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@ -1488,14 +1488,22 @@ builtin_round(self, args)
if (!PyArg_ParseTuple(args, "d|i:round", &x, &ndigits)) if (!PyArg_ParseTuple(args, "d|i:round", &x, &ndigits))
return NULL; return NULL;
f = 1.0; f = 1.0;
for (i = ndigits; --i >= 0; ) i = abs(ndigits);
while (--i >= 0)
f = f*10.0; f = f*10.0;
for (i = ndigits; ++i <= 0; ) if (ndigits < 0)
f = f*0.1; x /= f;
if (x >= 0.0)
return PyFloat_FromDouble(floor(x*f + 0.5) / f);
else else
return PyFloat_FromDouble(ceil(x*f - 0.5) / f); x *= f;
if (x >= 0.0)
x = floor(x + 0.5);
else
x = ceil(x - 0.5);
if (ndigits < 0)
x *= f;
else
x /= f;
return PyFloat_FromDouble(x);
} }
static PyObject * static PyObject *