Feature #16428: Add Array#uniq?, Enumerable#uniq?

• Status: Open
• Priority: Normal
• Assignee: -
• Target version: -

[kyanagi (Kouhei Yanagita)]

I propose Array#uniq?.

I often need to check if an array have duplicate elements.

This method returns true if no duplicates are found in self, otherwise returns false.
If a block is given, it will use the return value of the block for comparison.

This is equivalent to array.uniq.size == array.size, but faster.

% ~/tmp/r/bin/ruby -rbenchmark/ips -e 'a = Array.new(100) { rand(1000) }; Benchmark.ips { |x| x.report("uniq") { a.uniq.size == a.size }; x.report("uniq?") { a.uniq? } }'
Warming up --------------------------------------
                uniq    25.765k i/100ms
               uniq?    76.544k i/100ms
Calculating -------------------------------------
                uniq    278.144k (± 4.1%) i/s -      1.391M in   5.010858s
               uniq?    981.868k (± 5.1%) i/s -      4.975M in   5.081611s

I think the name uniq? is natural because Array already has uniq.

patch: https://github.com/ruby/ruby/pull/2762

[shevegen (Robert A. Heiler)]

I often need to check if an array have duplicate elements.

Makes sense to me; I have had situations where I needed this
too in the past (including situations for non-unique entries
in an Array), so I agree on the general use case opportunities
in this regard.

[duerst (Martin Dürst)]

I seem to member that many years ago, I made the same proposal, and Nobu created a patch, but unfortunately, I didn't find any traces anymore on this tracker or in my mail.

Anyway, I support this proposal. It's definitely an useful functionality, and it's clearly faster than doing it indirectly via #uniq.

[kyanagi (Kouhei Yanagita)]

• Subject changed from Add Array#uniq? to Add Array#uniq?, Enumerable#uniq?

Following a suggestion of Enumerable#uniq?, I also added Enumerable#uniq? to my patch.
Array#uniq? is left because it is faster than Enumerable#uniq?.