closures aren't cheap, srsly

inject_concat_vs_map.rb

require "benchmark"

arr = [1,2,3,4,5,6,7,8,9,0] * 100
GC.start

TESTS = 10_000
Benchmark.bmbm do |results|
  results.report("map:") { TESTS.times { arr.map { |i| i } } }
  results.report("inj:") { TESTS.times { a = []; arr.inject(a, :<<) } }
end

# Rehearsal ----------------------------------------
# map:   1.790000   0.020000   1.810000 (  2.070154)
# inj:   1.700000   0.010000   1.710000 (  1.854312)
# ------------------------------- total: 3.520000sec
# 
#            user     system      total        real
# map:   1.780000   0.010000   1.790000 (  1.839637)
# inj:   1.700000   0.010000   1.710000 (  1.752435)