Add another PartialEq example #51760

GuillaumeGomez · 2018-06-24T16:34:14Z

Centril · 2018-06-24T17:48:19Z

src/libcore/cmp.rs

@@ -95,6 +96,35 @@ use self::Ordering::*;
 /// assert!(b1 != b3);
 /// ```
 ///
+/// ##How can I implement it to compare with another type?


Space between ## and How and it => PartialEq imo

That's not the issue. ;)

rust-highfive · 2018-06-24T17:58:20Z

The job x86_64-gnu-llvm-3.9 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

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[01:16:28]    Doc-tests core
[01:16:41] 
[01:16:41] running 2093 tests
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rust-highfive · 2018-06-24T22:36:15Z

Your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

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[00:00:52] sha256:8c1f0882640438d1d5e0c0acc857fedd1a16de0d9ee943660aa40de5c9b49bad
[00:00:52] Attempting with retry: docker build --rm -t rust-ci -f /home/travis/build/rust-lang/rust/src/ci/docker/x86_64-gnu-llvm-3.9/Dockerfile /home/travis/build/rust-lang/rust/src/ci/docker
[00:00:52] Sending build context to Docker daemon  501.2kB
[00:00:52] Step 1/6 : FROM ubuntu:16.04
[00:00:52] Get https://registry-1.docker.io/v2/library/ubuntu/manifests/16.04: received unexpected HTTP status: 503 Service Unavailable
[00:00:53] Sending build context to Docker daemon  501.2kB
[00:00:53] Step 1/6 : FROM ubuntu:16.04
[00:00:53] Step 1/6 : FROM ubuntu:16.04
[00:00:53] Get https://registry-1.docker.io/v2/library/ubuntu/manifests/16.04: received unexpected HTTP status: 503 Service Unavailable
[00:00:55] Sending build context to Docker daemon  501.2kB
[00:00:55] Step 1/6 : FROM ubuntu:16.04
[00:00:55] Step 1/6 : FROM ubuntu:16.04
[00:00:56] Get https://registry-1.docker.io/v2/library/ubuntu/manifests/16.04: received unexpected HTTP status: 503 Service Unavailable
[00:00:59] Sending build context to Docker daemon  501.2kB
[00:00:59] Step 1/6 : FROM ubuntu:16.04
[00:00:59] Step 1/6 : FROM ubuntu:16.04
[00:00:59] Get https://registry-1.docker.io/v2/library/ubuntu/manifests/16.04: received unexpected HTTP status: 503 Service Unavailable
[00:01:03] Sending build context to Docker daemon  501.2kB
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[00:01:03] Step 1/6 : FROM ubuntu:16.04
[00:01:03] Get https://registry-1.docker.io/v2/library/ubuntu/manifests/16.04: received unexpected HTTP status: 503 Service Unavailable
[00:01:03] The command has failed after 5 attempts.

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 1.
travis_time:start:12abd860
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
---
travis_time:end:03b2475d:start=1529879746989628774,finish=1529879746996691113,duration=7062339
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travis_time:start:0e6474eb
$ head -30 ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
head: cannot open ‘./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers’ for reading: No such file or directory
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:2e1bf67f
$ dmesg | grep -i kill

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rust-highfive · 2018-06-25T10:17:11Z

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GuillaumeGomez · 2018-06-28T22:19:05Z

ping @steveklabnik

stokhos · 2018-07-06T19:23:44Z

Ping from triage! @steveklabnik @rust-lang/docs , we haven't heard from you for a while, will youh ave time to look into this PR?

stokhos · 2018-07-21T04:30:12Z

Ping from triage, @rust-lang/docs anyone would want to review this PR?

GuillaumeGomez · 2018-07-21T10:58:09Z

cc @QuietMisdreavus

QuietMisdreavus · 2018-07-22T17:58:24Z

src/libcore/cmp.rs

@@ -95,6 +96,35 @@ use self::Ordering::*;
 /// assert!(b1 != b3);
 /// ```
 ///
+/// ## How can I implement it to compare with another type?
+///
+/// This is pretty easy to do. Let's take back our previous code and modify it:


Not sure i agree with using "pretty easy" here. It's a poor phrase to use in documentation. How about something like this:

The type you can compare with is controlled by PartialEq's type parameter. For example, let's tweak our previous code a bit:

Then you can follow up below the example with something like:

By changing impl PartialEq for Book to impl PartialEq<BookFormat> for Book, we've changed what type we can use on the right side of the == operator. This lets us use it in the assert! statements at the bottom.

It would also be cool if you added one more example, combining them to show off that the same type can == to different types. Maybe continue with:

You can even combine these implementations to compare against both Book and BookFormat, like this:

(code sample with both PartialEq impls and both sets of assertions)

GuillaumeGomez · 2018-07-22T22:27:38Z

Took your sentences and added the new code! (which was a good idea!)

QuietMisdreavus · 2018-07-22T22:36:12Z

src/libcore/cmp.rs

+/// we've changed what type we can use on the right side of the `==` operator.
+/// This lets us use it in the `assert!` statements at the bottom.
+///
+/// Of course, you can implement `PartialEq` to have `==` operator on two


I'm not a fan of "of course" either. How about:

You can also combine these implementations to let the == operator work with two different types:

Fine by me! 😉

GuillaumeGomez · 2018-07-23T08:10:40Z

Updated.

steveklabnik

Sorry for missing the first ping :(

steveklabnik · 2018-07-23T13:12:18Z

src/libcore/cmp.rs

@@ -95,6 +96,76 @@ use self::Ordering::*;
 /// assert!(b1 != b3);
 /// ```
 ///
+/// ## How can I implement it to compare with another type?


This reads as awkward to me; can we get one last tweak?

/// ## How can I compare two different types?

steveklabnik · 2018-07-23T13:12:32Z

src/libcore/cmp.rs

+/// For example, let's tweak our previous code a bit:
+///
+/// ```
+/// enum BookFormat { Paperback, Hardback, Ebook }


is this how rustfmt formats this code?

I took the code above as is so I don't know?

steveklabnik · 2018-07-23T13:12:51Z

src/libcore/cmp.rs

+/// impl PartialEq<BookFormat> for Book {
+///     fn eq(&self, other: &BookFormat) -> bool {
+///         match (&self.format, other) {
+///            (&BookFormat::Paperback, &BookFormat::Paperback) => true,


does this code need the &s? I'd expect them to not these days.

It makes the code more clear.

steveklabnik · 2018-07-23T13:13:14Z

src/libcore/cmp.rs

+/// assert!(b1 != BookFormat::Ebook);
+/// ```
+///
+/// By changing impl `PartialEq` for `Book` to `impl PartialEq<BookFormat> for Book`,


the `s should be around the whole "impl PartialEq for book" here

TimNN · 2018-08-07T17:46:00Z

Ping from triage @GuillaumeGomez: Some changes have been requested to your PR.

GuillaumeGomez · 2018-08-08T08:15:15Z

Oh right! I'll update soon.

GuillaumeGomez · 2018-08-11T11:25:02Z

Updated to @steveklabnik's comments.

XAMPPRocky · 2018-08-21T13:28:58Z

Triage: @steveklabnik This PR requires your review.

GuillaumeGomez · 2018-08-21T14:50:29Z

Seems like I failed my rebase. I'll fix the conflicts.

GuillaumeGomez · 2018-08-21T21:24:49Z

Updated.

pietroalbini · 2018-08-27T16:00:29Z

Ping from triage! This PR needs a review, can @steveklabnik or someone else from @rust-lang/docs review this?

Resolved

QuietMisdreavus · 2018-08-27T18:01:37Z

Looks good to me! Let's get this merged.

@bors r+ rollup

bors · 2018-08-27T18:01:39Z

📌 Commit 3995bff has been approved by QuietMisdreavus

@steveklabnik