Remove `String#casecmp` part

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#123 opened on Apr 14, 2017 6 comments 2 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 1/5
Estimated time: Under an hour
Newbie friendliness: 35/100

Issue type: Documentation
Clarity: Mostly clear
Activity status: Stale
Tech stack: ruby
Domain: documentation

Research direction

No file, test, or entry point is named. First locate the documentation section for String#casecmp, review the Unicode examples and benchmark context, and remove the requested String#casecmp portion while preserving accurate guidance about String#downcase + ==.

Written by the indexing model from the issue text.

Description

The String#casecmp method does not work with Unicode (even in Ruby 2.4.1), this is written in the documentation.

Example:

'Привет'.casecmp('привет') # => -1

There is a method String#casecmp?, which works with Unicode.

Example:

'Привет'.casecmp?('привет') # => true

But String.casecmp? is slower:

Warming up --------------------------------------
String#downcase + ==   233.440k i/100ms
      String#casecmp   274.247k i/100ms
     String#casecmp?   219.906k i/100ms
Calculating -------------------------------------
String#downcase + ==      5.746M (± 1.7%) i/s -     28.947M in   5.039252s
      String#casecmp      6.942M (± 1.8%) i/s -     34.829M in   5.019073s
     String#casecmp?      4.517M (± 2.6%) i/s -     22.650M in   5.017864s

Comparison:
      String#casecmp:  6941676.9 i/s
String#downcase + ==:  5745893.8 i/s - 1.21x  slower
     String#casecmp?:  4517314.3 i/s - 1.54x  slower

Code

require 'benchmark/ips'

SLUG = 'ABCD'

def slow
  SLUG.downcase == 'abcd'
end

def fast
  SLUG.casecmp('abcd') == 0
end

def another
  SLUG.casecmp?('abcd')
end

Benchmark.ips do |x|
  x.report('String#downcase + ==') { slow }
  x.report('String#casecmp')       { fast }
  x.report('String#casecmp?')      { another }
  x.compare!
end

So, String#downcase + == is good compromise.

Dominant language: Ruby
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