Tapbench.rb

require 'benchmark/ips'
​
MYARRAY = [["a", ["b", nil, "c", ["d"]]]]
​
Benchmark.ips do |x|
  x.report("before") { 
    array = MYARRAY.dup
    array.flatten!
    array.uniq!
    array.compact!
    array 
  }
  x.report("after ") { 
    array = MYARRAY.dup
    array.tap(&:flatten!).tap(&:uniq!).tap(&:compact!) 
  }
  x.compare!
end
# Warming up --------------------------------------
#               before    35.455k i/100ms
#               after     32.321k i/100ms
# Calculating -------------------------------------
#               before    393.043k (± 4.5%) i/s -      1.985M in   5.062618s
#               after     371.538k (± 2.2%) i/s -      1.875M in   5.048124s
​
# Comparison:
#               before:   393043.0 i/s
#               after :   371537.7 i/s - same-ish: difference falls within error
​