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Correct frexp() docs for zero and non-finite numbers#149753

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serhiy-storchaka merged 5 commits into
python:mainfrom
skirpichev:fix-frexp-docs
May 31, 2026
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Correct frexp() docs for zero and non-finite numbers#149753
serhiy-storchaka merged 5 commits into
python:mainfrom
skirpichev:fix-frexp-docs

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@skirpichev skirpichev commented May 13, 2026

The current version claims, that mantissa in such cases satisfies 0.5 <= abs(m) < 1. That's wrong:

>>> from math import frexp, inf, nan
>>> frexp(inf)
(inf, 0)
>>> frexp(-inf)
(-inf, 0)
>>> frexp(nan)
(nan, 0)

@skirpichev
Correct frexp() docs for non-finite numbers
22657c4 
The current version claims, that mantissa in such
cases satisfies 0.5 <= abs(m) < 1.  That's wrong:

```pycon
>>> from math import frexp, inf, nan
>>> frexp(inf)
(inf, 0)
>>> frexp(-inf)
(-inf, 0)
>>> frexp(nan)
(nan, 0)
```
@skirpichev skirpichev added skip issue skip news needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes needs backport to 3.15 pre-release feature fixes, bugs and security fixes labels May 13, 2026
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skirpichev commented May 13, 2026

CC @StanFromIreland per experts index.

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read-the-docs-community Bot commented May 13, 2026 •
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StanFromIreland commented May 13, 2026

CC @StanFromIreland per experts index.

Hi Sergey, sorry but I'm not a math expert :-( The "documentation" is generally referring to it the infra.

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skirpichev commented May 14, 2026

CC @serhiy-storchaka

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LGTM. 👍

@serhiy-storchaka serhiy-storchaka enabled auto-merge (squash) May 31, 2026 07:08
@serhiy-storchaka serhiy-storchaka changed the title Correct frexp() docs for non-finite numbers Correct frexp() docs for zero and non-finite numbers May 31, 2026
@serhiy-storchaka serhiy-storchaka merged commit 5b5ffce into python:main May 31, 2026
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miss-islington-app Bot commented May 31, 2026

Thanks @skirpichev for the PR, and @serhiy-storchaka for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14, 3.15.
🐍🍒⛏🤖

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miss-islington-app Bot commented May 31, 2026

Sorry, @skirpichev and @serhiy-storchaka, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 5b5ffce05c211a5b0b74cd95eeb4c463614ee136 3.14

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bedevere-app Bot commented May 31, 2026

GH-150652 is a backport of this pull request to the 3.15 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.15 pre-release feature fixes, bugs and security fixes label May 31, 2026
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miss-islington-app Bot commented May 31, 2026

Sorry, @skirpichev and @serhiy-storchaka, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 5b5ffce05c211a5b0b74cd95eeb4c463614ee136 3.13

@skirpichev skirpichev self-assigned this May 31, 2026
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bedevere-app Bot commented May 31, 2026

GH-150653 is a backport of this pull request to the 3.14 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label May 31, 2026
@skirpichev skirpichev deleted the fix-frexp-docs branch May 31, 2026 07:37
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bedevere-app Bot commented May 31, 2026

GH-150654 is a backport of this pull request to the 3.13 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.13 bugs and security fixes label May 31, 2026
@skirpichev skirpichev removed their assignment May 31, 2026
serhiy-storchaka pushed a commit that referenced this pull request May 31, 2026
@skirpichev
[3.13] Correct frexp() docs for zero and non-finite numbers (GH-149753)…
70a4e19 
… (GH-150654)

0.5 <= abs(m) < 1 is only true for finite nonzero numbers
(cherry picked from commit 5b5ffce)
serhiy-storchaka pushed a commit that referenced this pull request May 31, 2026
@skirpichev
[3.14] Correct frexp() docs for zero and non-finite numbers (GH-149753)…
942ba2d 
… (GH-150653)

0.5 <= abs(m) < 1 is only true for finite nonzero numbers
(cherry picked from commit 5b5ffce)
serhiy-storchaka pushed a commit that referenced this pull request May 31, 2026
@miss-islington @skirpichev
[3.15] Correct frexp() docs for zero and non-finite numbers (GH-149753)…
c5655df 
… (GH-150652)

0.5 <= abs(m) < 1 is only true for finite nonzero numbers
(cherry picked from commit 5b5ffce)

Co-authored-by: Sergey B Kirpichev <skirpichev@gmail.com>
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