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More practical examples for Option::and_then & Result::and_then#93851

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cyqsimon:option-examples
Feb 13, 2022
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More practical examples for Option::and_then & Result::and_then#93851
bors merged 8 commits intorust-lang:masterfrom
cyqsimon:option-examples

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@cyqsimon cyqsimon commented Feb 10, 2022 •
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To be blatantly honest, I think the current example given for Option::and_then is objectively terrible. (No offence to whoever wrote them initially.)

fn sq(x: u32) -> Option<u32> { Some(x * x) }
fn nope(_: u32) -> Option<u32> { None }

assert_eq!(Some(2).and_then(sq).and_then(sq), Some(16));
assert_eq!(Some(2).and_then(sq).and_then(nope), None);
assert_eq!(Some(2).and_then(nope).and_then(sq), None);
assert_eq!(None.and_then(sq).and_then(sq), None);

Current example:

  • does not demonstrate that and_then converts Option<T> to Option<U>
  • is far removed from any realistic code
  • generally just causes more confusion than it helps

So I replaced them with two blocks:

  • the first one shows basic usage (including the type conversion)
  • the second one shows an example of typical usage

Same thing with Result::and_then.

Hopefully this helps with clarity.

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rust-highfive commented Feb 10, 2022

r? @scottmcm

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@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Feb 10, 2022
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scottmcm commented Feb 10, 2022

Thanks for the PR! These look good to me.

@bors r+ rollup

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bors commented Feb 10, 2022

📌 Commit 73a5f01 has been approved by scottmcm

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 10, 2022
@cyqsimon cyqsimon closed this Feb 10, 2022
@cyqsimon cyqsimon deleted the option-examples branch February 10, 2022 10:00
@cyqsimon cyqsimon restored the option-examples branch February 10, 2022 10:01
@cyqsimon cyqsimon reopened this Feb 10, 2022
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cyqsimon commented Feb 10, 2022

Oops. I renamed the branch on GitHub expecting this PR to be unaffected. Sry for any inconvenience.

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cyqsimon commented Feb 10, 2022

I also updated examples for Result::and_then, and thought I'd squeeze that into this PR as well. Well turns out I was somewhat too slow. Hopefully I haven't messed up the workflow too bad.

@cyqsimon cyqsimon changed the title More practical examples for Option::and_then More practical examples for Option::and_then & Result::and_then Feb 10, 2022
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scottmcm commented Feb 11, 2022

@rustbot author

I'm going to mark this as author, so you can continue making additions.

Once you're at the final version, use @rustbot ready to mark it as review-ready.

@rustbot rustbot added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Feb 11, 2022
@scottmcm scottmcm removed the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Feb 11, 2022
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cyqsimon commented Feb 11, 2022

My apologies, I really should have made it a draft PR before everything is ready. I will do better next time. Sorry for the disruptions I caused.

I'm happy with the current state of this PR and will refrain from making further edits. Thanks.

@rustbot ready

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 11, 2022
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Just a couple of thoughts on the Result examples.

I don't think they're MUSTs, so if you'd rather not make changes then comment and re-ready the PR.

@scottmcm scottmcm added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 12, 2022
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cyqsimon commented Feb 12, 2022

@rustbot ready

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 12, 2022
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scottmcm commented Feb 12, 2022

Thanks for the updates!

@bors r+

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bors commented Feb 12, 2022

📌 Commit f6f93fd has been approved by scottmcm

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 12, 2022
@matthiaskrgr matthiaskrgr mentioned this pull request Feb 13, 2022
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bors added a commit to rust-lang-ci/rust that referenced this pull request Feb 13, 2022
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Auto merge of rust-lang#93956 - matthiaskrgr:rollup-zfk35hb, r=matthi…
9a60099 
…askrgr

Rollup of 9 pull requests

Successful merges:

 - rust-lang#89926 (make `Instant::{duration_since, elapsed, sub}` saturating and remove workarounds)
 - rust-lang#90532 (More informative error message for E0015)
 - rust-lang#93810 (Improve chalk integration)
 - rust-lang#93851 (More practical examples for `Option::and_then` & `Result::and_then`)
 - rust-lang#93885 (bootstrap.py: Suggest disabling download-ci-llvm option if url fails to download)
 - rust-lang#93886 (Stabilise inherent_ascii_escape (FCP in rust-lang#77174))
 - rust-lang#93930 (add link to format_args! when mention it in docs)
 - rust-lang#93936 (Couple of driver cleanups)
 - rust-lang#93944 (Don't relabel to a team if there is already a team label)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 783b56b into rust-lang:master Feb 13, 2022
@rustbot rustbot added this to the 1.60.0 milestone Feb 13, 2022
@cyqsimon cyqsimon deleted the option-examples branch February 14, 2022 05:53
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