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Diffstat (limited to 'Doc/library/math.rst')
| -rw-r--r-- | Doc/library/math.rst | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/Doc/library/math.rst b/Doc/library/math.rst index c9f2a38..c4c1800 100644 --- a/Doc/library/math.rst +++ b/Doc/library/math.rst @@ -226,6 +226,8 @@ Number-theoretic and representation functions * ``math.nextafter(x, 0.0)`` goes towards zero. * ``math.nextafter(x, math.copysign(math.inf, x))`` goes away from zero. + See also :func:`math.ulp`. + .. versionadded:: 3.9 .. function:: perm(n, k=None) @@ -284,6 +286,30 @@ Number-theoretic and representation functions :class:`~numbers.Integral` (usually an integer). Delegates to :meth:`x.__trunc__() <object.__trunc__>`. +.. function:: ulp(x) + + Return the value of the least significant bit of the float *x*: + + * If *x* is a NaN (not a number), return *x*. + * If *x* is negative, return ``ulp(-x)``. + * If *x* is a positive infinity, return *x*. + * If *x* is equal to zero, return the smallest positive + *denormalized* representable float (smaller than the minimum positive + *normalized* float, :data:`sys.float_info.min <sys.float_info>`). + * If *x* is equal to the largest positive representable float, + return the value of the least significant bit of *x*, such that the first + float smaller than *x* is ``x - ulp(x)``. + * Otherwise (*x* is a positive finite number), return the value of the least + significant bit of *x*, such that the first float bigger than *x* + is ``x + ulp(x)``. + + ULP stands for "Unit in the Last Place". + + See also :func:`math.nextafter` and :data:`sys.float_info.epsilon + <sys.float_info>`. + + .. versionadded:: 3.9 + Note that :func:`frexp` and :func:`modf` have a different call/return pattern than their C equivalents: they take a single argument and return a pair of |