`_di_below, _di_above`

Synopsis#include <flint/double_interval.h>

double _di_below(double x)source

double _di_above(double x)source

Return a lower respectively upper bound for any real number whose round-to-nearest value is $x$ . _di_below returns $x - (|x| + 10^{-300}) \cdot 2^{-51}$ for $x \le 10^{300}$ (rounded to nearest), $10^{300}$ for larger $x$ including $+\infty$ , and $-\infty$ for NaN (which arises from $\infty - \infty$ in the endpoint arithmetic); _di_above is symmetric.

Cite this page

The FLINT team, “_di_below, _di_above (double_interval.h),” FLINT: Fast Library for Number Theory, documentation, version 3.7.0-dev, 2026. https://flintlib.org/doc/double_interval/_di_below.html (generated 2026-11-02).

@misc{flint-doc-double-interval-di-below,
  author       = {{The FLINT team}},
  title        = {{\_di\_below, \_di\_above (double\_interval.h)}},
  howpublished = {FLINT: Fast Library for Number Theory, documentation, version 3.7.0-dev},
  year         = {2026},
  url          = {https://flintlib.org/doc/double_interval/_di_below.html},
  note         = {Generated 2026-11-02}
}

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