implement .trailing_ones(), .leading_ones() #55715

yoshuawuyts · Nov 6, 2018

Hi!

This patch implements .trailing_ones() and .leading_ones() to all number types as counterparts to the .leading_zeros(), and .trailing_zeros() methods.

I posted a pre-RFC for these changes on internals, but the consensus seemed to be these changes would be small enough that no RFC was needed. So hence this patch!

I've never written a PR for Rustc before, so I hope I'm doing everything right. I realize this patch is probably not good enough to land as-is, so I had a few questions:

Should external tests be added, or are doctests enough? If yes: where should they be added?
I'm not sure what the right stability attribute would be for these methods. The tidy checks are pointing out it's malformed, but I'm not sure what the correct form would be.

Thanks heaps!

rust-highfive · Nov 6, 2018

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @KodrAus (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

killercup · Nov 6, 2018

killercup reviewed Nov 6, 2018

View changes

src/libcore/num/mod.rs

killercup · Nov 6, 2018

src/libcore/num/mod.rs

+assert_eq!(n.leading_ones(), 0);",
+$EndFeature, "
+```"),
+            #[unstable(feature = "leading_ones_trailing_ones", issue = "0")]


Not on the libs team but it might be a good idea to open an issue so you have a non-zero number you can refer to here :)

rust-highfive · Nov 6, 2018

The job x86_64-gnu-llvm-5.0 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.

Click to expand the log.

travis_time:end:1e8413b0:start=1541510648620989342,finish=1541510840203116873,duration=191582127531
$ git checkout -qf FETCH_HEAD
travis_fold:end:git.checkout

Encrypted environment variables have been removed for security reasons.
See https://docs.travis-ci.com/user/pull-requests/#Pull-Requests-and-Security-Restrictions
$ export SCCACHE_BUCKET=rust-lang-ci-sccache2
$ export SCCACHE_REGION=us-west-1
Setting environment variables from .travis.yml
$ export IMAGE=x86_64-gnu-llvm-5.0
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---
[01:30:20] ---- num/mod.rs - num::i128::leading_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.leading_ones(), 1);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::i128::leading_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] note: Run with `RUST_BACKTRACE=1` for a backtrace.
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::i128::trailing_ones (line 45) stdout ----
[01:30:20] ---- num/mod.rs - num::i128::trailing_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.trailing_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::i128::trailing_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::i16::leading_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.leading_ones(), 1);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::i16::leading_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::i16::trailing_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.trailing_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::i16::trailing_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::i32::leading_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.leading_ones(), 1);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::i32::leading_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::i32::trailing_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.trailing_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::i32::trailing_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::i64::leading_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.leading_ones(), 1);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::i64::leading_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::i64::trailing_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.trailing_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::i64::trailing_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::i8::leading_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.leading_ones(), 1);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::i8::leading_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::i8::trailing_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.trailing_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::i8::trailing_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::isize::leading_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.leading_ones(), 1);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::isize::leading_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::isize::trailing_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.trailing_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::isize::trailing_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::u128::leading_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.leading_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::u128::leading_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::u128::trailing_ones (line 46) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:49:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.trailing_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::u128::trailing_ones (line 46)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::u16::leading_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.leading_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::u16::leading_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::u16::trailing_ones (line 46) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:49:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.trailing_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::u16::trailing_ones (line 46)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::u32::leading_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.leading_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::u32::leading_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::u32::trailing_ones (line 46) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:49:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.trailing_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::u32::trailing_ones (line 46)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::u64::leading_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.leading_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::u64::leading_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::u64::trailing_ones (line 46) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:49:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.trailing_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::u64::trailing_ones (line 46)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::u8::leading_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.leading_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::u8::leading_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::u8::trailing_ones (line 46) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:49:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.trailing_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::u8::trailing_ones (line 46)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::usize::leading_ones (line 45) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:48:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.leading_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::usize::leading_ones (line 45)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] ---- num/mod.rs - num::usize::trailing_ones (line 46) stdout ----
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20] error[E0658]: use of unstable library feature 'leading_ones_trailing_ones'
[01:30:20]  --> num/mod.rs:49:14
[01:30:20]   |
[01:30:20] 6 | assert_eq!(n.trailing_ones(), 2);
[01:30:20]   |
[01:30:20]   |
[01:30:20]   = help: add #![feature(leading_ones_trailing_ones)] to the crate attributes to enable
[01:30:20] thread 'num/mod.rs - num::usize::trailing_ones (line 46)' panicked at 'couldn't compile the test', librustdoc/test.rs:323:13
[01:30:20] 
[01:30:20] 
[01:30:20] failures:
---
[01:30:20] 
[01:30:20] error: test failed, to rerun pass '--doc'
[01:30:20] 
[01:30:20] 
[01:30:20] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "test" "--target" "x86_64-unknown-linux-gnu" "-j" "4" "--release" "--locked" "--color" "always" "--features" "panic-unwind backtrace" "--manifest-path" "/checkout/src/libstd/Cargo.toml" "-p" "core" "--" "--quiet"
[01:30:20] 
[01:30:20] 
[01:30:20] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
[01:30:20] Build completed unsuccessfully in 0:38:59
[01:30:20] Build completed unsuccessfully in 0:38:59
[01:30:20] make: *** [check] Error 1
[01:30:20] Makefile:58: recipe for target 'check' failed

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:055fe321
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
---
travis_time:end:04fa4b4c:start=1541516273128371973,finish=1541516273132975233,duration=4603260
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:12bcc87c
$ ln -s . checkout && for CORE in obj/cores/core.*; do EXE=$(echo $CORE | sed 's|obj/cores/core\.[0-9]*\.!checkout!\(.*\)|\1|;y|!|/|'); if [ -f "$EXE" ]; then printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" "$CORE"; gdb --batch -q -c "$CORE" "$EXE" -iex 'set auto-load off' -iex 'dir src/' -iex 'set sysroot .' -ex bt -ex q; echo travis_fold":"end:crashlog; fi; done || true
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:10dae0d0
travis_time:start:10dae0d0
$ cat ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
cat: ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers: No such file or directory
travis_fold:end:after_failure.5
travis_fold:start:after_failure.6
travis_time:start:1d1a7b8d
$ dmesg | grep -i kill

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

scottmcm · Nov 6, 2018

scottmcm reviewed Nov 6, 2018

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scottmcm · Nov 6, 2018

src/libcore/num/mod.rs

+```
+", $Feature, "let n = 0b10110011", stringify!($SelfT), ";
+
+assert_eq!(n.leading_ones(), 1);",


I don't think this will pass -- this will have no leading ones for any type size but u8.

scottmcm · Nov 6, 2018

scottmcm reviewed Nov 6, 2018

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scottmcm · Nov 6, 2018

src/libcore/num/mod.rs

+Basic usage:
+
+```
+", $Feature, "let n = 0b10110011", stringify!($SelfT), ";


Tidy is saying that you need #![feature(leading_ones_trailing_ones)] in the doctests.

XAMPPRocky · Nov 25, 2018

Triage; @yoshuawuyts Hello, have you been able to get back this PR?

yoshuawuyts · Nov 27, 2018

@Aaronepower Thanks for reaching out! Ooph, no -- I've been super busy, and about to go on holiday. If it's not too much trouble, I'd love to keep this open for a few more weeks so I can hack on it once I'm back.

Dylan-DPC · Jan 7, 2019

ping from triage @yoshuawuyts any updates on this?

yoshuawuyts · Jan 8, 2019

@Dylan-DPC not yet; haven't forgotten about it! -- I'm planning to tackle this next week! 🎉

TimNN · Jan 22, 2019

Ping from triage @yoshuawuyts: What is the status of this PR?

Centril · Jan 27, 2019

Centril reviewed Jan 27, 2019

View changes

Centril · Jan 27, 2019

src/libcore/num/mod.rs

+$EndFeature, "
+```"),
+            #[unstable(feature = "leading_ones_trailing_ones", issue = "0")]
+            #[rustc_const_unstable(feature = "const_int_ops")]


I'd just remove this; I think it's fairly certain that we'll want it to be const fn when stabilizing.

Centril · Jan 27, 2019

src/libcore/num/mod.rs

+$EndFeature, "
+```"),
+            #[unstable(feature = "leading_ones_trailing_ones", issue = "0")]
+            #[rustc_const_unstable(feature = "const_int_ops")]


Same, I'd remove this line.

Centril · Jan 27, 2019

src/libcore/num/mod.rs

+assert_eq!(n.leading_ones(), 2);", $EndFeature, "
+```"),
+            #[unstable(feature = "leading_ones_trailing_ones", issue = "0")]
+            #[rustc_const_unstable(feature = "const_int_ops")]


and here...

Centril · Jan 27, 2019

src/libcore/num/mod.rs

+assert_eq!(n.trailing_ones(), 2);", $EndFeature, "
+```"),
+            #[unstable(feature = "leading_ones_trailing_ones", issue = "0")]
+            #[rustc_const_unstable(feature = "const_int_ops")]


yoshuawuyts · Jan 29, 2019

Update: I've spent some time building this out again yesterday, but ran into build problems with Rust itself. Sorry this is taking a while!

yoshuawuyts · Jan 29, 2019

Created an issue for this PR in #57969. If someone else would like to carry this PR over the finish line that'd be grand! -- I feel we're really close; it just requires passing lints + feature labels.

Dylan-DPC · Feb 25, 2019

ping from triage @yoshuawuyts closing this due to inactivity and since you are not planning of taking this forward. Thanks!

rust-highfive assigned KodrAus Nov 6, 2018

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yoshuawuyts force-pushed the yoshuawuyts:trailing_ones_trailing_zeros branch 2 times, most recently from 88eec03 to 7fb7422 Nov 6, 2018

implement .trailing_ones(), .leading_ones()
Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

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yoshuawuyts referenced this pull request Jan 29, 2019
Open
Tracking issue for `.trailing_ones()` + `leading_ones()` #57969

Dylan-DPC closed this Feb 25, 2019

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implement .trailing_ones(), .leading_ones() #55715

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killercup reviewed Nov 6, 2018

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yoshuawuyts force-pushed the yoshuawuyts:trailing_ones_trailing_zeros branch 2 times, most recently from `88eec03` to `7fb7422` Nov 6, 2018

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