Interpolate '' instead of nil when multiple is false.

"my string #{nil}" results in an additional '' string allocation, I'm
guessing because the nil has to be converted to a string.

"my string #{'[]' if multiple}" results in "my string #{nil}" if
multiple is false. Doing "my string #{''}" does not result in an extra
string allocation. I moved the if multiple logic into a method so I only
had to make the change once.

```ruby
begin
  require "bundler/inline"
rescue LoadError => e
  $stderr.puts "Bundler version 1.10 or later is required. Please update
                your Bundler"
  raise e
end

gemfile(true) do
  source "https://rubygems.org"

  gem "benchmark-ips"
  gem "rails"
end

def allocate_count
  GC.disable
  before = ObjectSpace.count_objects
  yield
  after = ObjectSpace.count_objects
  after.each { |k,v| after[k] = v - before[k] }
  after[:T_HASH] -= 1 # probe effect - we created the before hash.
  GC.enable
  result = after.reject { |k,v| v == 0 }
  GC.start
  result
end

@html_options = {}

def master_version(multiple=nil)
  "hi#{"[]" if multiple}"
end

def fast_version(multiple=nil)
  str = multiple ? "[]" : ''
  "hi#{str}"
end

def test
  puts "master_version"
  puts allocate_count { 1000.times { master_version } }
  puts "master_version with arg"
  puts allocate_count { 1000.times { master_version(' there') } }
  puts "fast_version"
  puts allocate_count { 1000.times { fast_version } }
  puts "fast_version with arg"
  puts allocate_count { 1000.times { fast_version(' there') } }

  Benchmark.ips do |x|
    x.report("master_version") { master_version }
    x.report("master_version with arg") { master_version(' there') }
    x.report("fast_version")     { fast_version }
    x.report("fast_version with arg")     { fast_version(' there') }
    x.compare!
  end
end

test
```

results:
```ruby
master_version
{:FREE=>-1981, :T_STRING=>2052}
master_version with arg
{:FREE=>-1001, :T_STRING=>1000}
fast_version
{:FREE=>-1001, :T_STRING=>1000}
fast_version with arg
{:FREE=>-1001, :T_STRING=>1000}
Warming up --------------------------------------
      master_version   138.851k i/100ms
master_version with arg
                       164.029k i/100ms
        fast_version   165.737k i/100ms
fast_version with arg
                       167.016k i/100ms
Calculating -------------------------------------
      master_version      2.464M (±14.7%) i/s -     11.941M in   5.023307s
master_version with arg
                          3.754M (± 8.5%) i/s -     18.699M in   5.021354s
        fast_version      3.449M (±11.7%) i/s -     17.071M in   5.033312s
fast_version with arg
                          3.636M (± 6.9%) i/s -     18.205M in   5.034792s

Comparison:
master_version with arg:  3753896.1 i/s
fast_version with arg:  3636094.5 i/s - same-ish: difference falls within error
        fast_version:  3448766.2 i/s - same-ish: difference falls within error
      master_version:  2463857.3 i/s - 1.52x  slower
```

0 files changed, 0 insertions, 0 deletions