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gh-85417: Clarify behaviour on branch cuts in cmath module #102046

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mdickinson
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@mdickinson mdickinson commented Feb 19, 2023

This PR updates the cmath module documentation to reflect the reality that Python is almost always (and as far as I can tell, that "almost" can be omitted) running on a machine whose C double supports signed zeros.

  • Removes misleading references to functions being continuous from above / below / the left / the right at branch cuts
  • Expands the note on branch cuts at the top of the module to explain the double-sided sign-of-zero-based behaviour

Closes #85417

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@skirpichev
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#102047 is more or less same, but less verbose.

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@mdickinson mdickinson merged commit b513c46 into python:main Feb 19, 2023
@mdickinson mdickinson deleted the gh-85417-fix-cmath-branch-cut-documentation branch February 19, 2023 19:15
jaraco pushed a commit to jaraco/cpython that referenced this pull request Feb 20, 2023
…hon#102046)

This PR updates the cmath module documentation to reflect the reality that Python is almost always (and as far as I can tell, that "almost" can be omitted) running on a machine whose C double supports signed zeros.

* Removes misleading references to functions being continuous from above / below / the left / the right at branch cuts
* Expands the note on branch cuts at the top of the module documentation to explain the double-sided sign-of-zero-based behaviour
carljm added a commit to carljm/cpython that referenced this pull request Feb 20, 2023
* main: (60 commits)
  pythongh-102056: Fix a few bugs in error handling of exception printing code (python#102078)
  pythongh-102011: use sys.exception() instead of sys.exc_info() in docs where possible (python#102012)
  pythongh-101566: Sync with zipp 3.14. (pythonGH-102018)
  pythonGH-99818: improve the documentation for zipfile.Path and Traversable (pythonGH-101589)
  pythongh-88233: zipfile: handle extras after a zip64 extra (pythonGH-96161)
  pythongh-101981: Apply HOMEBREW related environment variables (pythongh-102074)
  pythongh-101907: Stop using `_Py_OPCODE` and `_Py_OPARG` macros (pythonGH-101912)
  pythongh-101819: Adapt _io types to heap types, batch 1 (pythonGH-101949)
  pythongh-101981: Build macOS as recommended by the devguide (pythonGH-102070)
  pythongh-97786: Fix compiler warnings in pytime.c (python#101826)
  pythongh-101578: Amend PyErr_{Set,Get}RaisedException docs (python#101962)
  Misc improvements to the float tutorial (pythonGH-102052)
  pythongh-85417: Clarify behaviour on branch cuts in cmath module (python#102046)
  pythongh-100425: Update tutorial docs related to sum() accuracy (FH-101854)
  Add missing 'is' to `cmath.log()` docstring (python#102049)
  pythongh-100210: Correct the comment link for unescaping HTML (python#100212)
  pythongh-97930: Also include subdirectory in makefile. (python#102030)
  pythongh-99735: Use required=True in argparse subparsers example (python#100927)
  Fix incorrectly documented attribute in csv docs (python#101250)
  pythonGH-84783: Make the slice object hashable (pythonGH-101264)
  ...
carljm added a commit to carljm/cpython that referenced this pull request Feb 22, 2023
* main: (225 commits)
  pythongh-102056: Fix a few bugs in error handling of exception printing code (python#102078)
  pythongh-102011: use sys.exception() instead of sys.exc_info() in docs where possible (python#102012)
  pythongh-101566: Sync with zipp 3.14. (pythonGH-102018)
  pythonGH-99818: improve the documentation for zipfile.Path and Traversable (pythonGH-101589)
  pythongh-88233: zipfile: handle extras after a zip64 extra (pythonGH-96161)
  pythongh-101981: Apply HOMEBREW related environment variables (pythongh-102074)
  pythongh-101907: Stop using `_Py_OPCODE` and `_Py_OPARG` macros (pythonGH-101912)
  pythongh-101819: Adapt _io types to heap types, batch 1 (pythonGH-101949)
  pythongh-101981: Build macOS as recommended by the devguide (pythonGH-102070)
  pythongh-97786: Fix compiler warnings in pytime.c (python#101826)
  pythongh-101578: Amend PyErr_{Set,Get}RaisedException docs (python#101962)
  Misc improvements to the float tutorial (pythonGH-102052)
  pythongh-85417: Clarify behaviour on branch cuts in cmath module (python#102046)
  pythongh-100425: Update tutorial docs related to sum() accuracy (FH-101854)
  Add missing 'is' to `cmath.log()` docstring (python#102049)
  pythongh-100210: Correct the comment link for unescaping HTML (python#100212)
  pythongh-97930: Also include subdirectory in makefile. (python#102030)
  pythongh-99735: Use required=True in argparse subparsers example (python#100927)
  Fix incorrectly documented attribute in csv docs (python#101250)
  pythonGH-84783: Make the slice object hashable (pythonGH-101264)
  ...
@mdickinson mdickinson added needs backport to 3.10 only security fixes needs backport to 3.11 only security fixes labels Feb 26, 2023
@miss-islington
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Thanks @mdickinson for the PR 🌮🎉.. I'm working now to backport this PR to: 3.10.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

@miss-islington
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Thanks @mdickinson for the PR 🌮🎉.. I'm working now to backport this PR to: 3.11.
🐍🍒⛏🤖

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Feb 26, 2023
…honGH-102046)

This PR updates the cmath module documentation to reflect the reality that Python is almost always (and as far as I can tell, that "almost" can be omitted) running on a machine whose C double supports signed zeros.

* Removes misleading references to functions being continuous from above / below / the left / the right at branch cuts
* Expands the note on branch cuts at the top of the module documentation to explain the double-sided sign-of-zero-based behaviour
(cherry picked from commit b513c46)

Co-authored-by: Mark Dickinson <dickinsm@gmail.com>
@bedevere-bot
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GH-102275 is a backport of this pull request to the 3.10 branch.

@bedevere-bot bedevere-bot removed the needs backport to 3.10 only security fixes label Feb 26, 2023
@bedevere-bot
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GH-102276 is a backport of this pull request to the 3.11 branch.

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Feb 26, 2023
…honGH-102046)

This PR updates the cmath module documentation to reflect the reality that Python is almost always (and as far as I can tell, that "almost" can be omitted) running on a machine whose C double supports signed zeros.

* Removes misleading references to functions being continuous from above / below / the left / the right at branch cuts
* Expands the note on branch cuts at the top of the module documentation to explain the double-sided sign-of-zero-based behaviour
(cherry picked from commit b513c46)

Co-authored-by: Mark Dickinson <dickinsm@gmail.com>
@bedevere-bot bedevere-bot removed the needs backport to 3.11 only security fixes label Feb 26, 2023
mdickinson added a commit that referenced this pull request Feb 26, 2023
…-102046) (#102275)

gh-85417: Clarify behaviour on branch cuts in cmath module (GH-102046)

This PR updates the cmath module documentation to reflect the reality that Python is almost always (and as far as I can tell, that "almost" can be omitted) running on a machine whose C double supports signed zeros.

* Removes misleading references to functions being continuous from above / below / the left / the right at branch cuts
* Expands the note on branch cuts at the top of the module documentation to explain the double-sided sign-of-zero-based behaviour
(cherry picked from commit b513c46)

Co-authored-by: Mark Dickinson <dickinsm@gmail.com>
mdickinson added a commit that referenced this pull request Feb 26, 2023
…-102046) (#102276)

gh-85417: Clarify behaviour on branch cuts in cmath module (GH-102046)

This PR updates the cmath module documentation to reflect the reality that Python is almost always (and as far as I can tell, that "almost" can be omitted) running on a machine whose C double supports signed zeros.

* Removes misleading references to functions being continuous from above / below / the left / the right at branch cuts
* Expands the note on branch cuts at the top of the module documentation to explain the double-sided sign-of-zero-based behaviour
(cherry picked from commit b513c46)

Co-authored-by: Mark Dickinson <dickinsm@gmail.com>
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cmath module documentation is misleading on branch cuts
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