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Diffstat (limited to 'Doc/library/math.rst')
| -rw-r--r-- | Doc/library/math.rst | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/Doc/library/math.rst b/Doc/library/math.rst index 6be61c99..2ecee89 100644 --- a/Doc/library/math.rst +++ b/Doc/library/math.rst @@ -244,19 +244,21 @@ Number-theoretic and representation functions ``False`` otherwise. Whether or not two values are considered close is determined according to - given absolute and relative tolerances. + given absolute and relative tolerances. If no errors occur, the result will + be: ``abs(a-b) <= max(rel_tol * max(abs(a), abs(b)), abs_tol)``. *rel_tol* is the relative tolerance -- it is the maximum allowed difference between *a* and *b*, relative to the larger absolute value of *a* or *b*. For example, to set a tolerance of 5%, pass ``rel_tol=0.05``. The default tolerance is ``1e-09``, which assures that the two values are the same - within about 9 decimal digits. *rel_tol* must be greater than zero. - - *abs_tol* is the minimum absolute tolerance -- useful for comparisons near - zero. *abs_tol* must be at least zero. - - If no errors occur, the result will be: - ``abs(a-b) <= max(rel_tol * max(abs(a), abs(b)), abs_tol)``. + within about 9 decimal digits. *rel_tol* must be nonnegative and less + than ``1.0``. + + *abs_tol* is the absolute tolerance; it defaults to ``0.0`` and it must be + nonnegative. When comparing ``x`` to ``0.0``, ``isclose(x, 0)`` is computed + as ``abs(x) <= rel_tol * abs(x)``, which is ``False`` for any ``x`` and + rel_tol less than ``1.0``. So add an appropriate positive abs_tol argument + to the call. The IEEE 754 special values of ``NaN``, ``inf``, and ``-inf`` will be handled according to IEEE rules. Specifically, ``NaN`` is not considered |