Ruby inmutable array concatenation. A prove benchmark.

bench.rb

# ruby --version
# ruby 2.6.3p62


require 'benchmark'

def without_splat(a, b, c); end

def with_splat(*a); end

Benchmark.bm do |x|
  x.report do
    (1..100_000).each do |_i|
      without_splat(1, 2, 3)
    end
  end
end

# user     system      total        real
# 0.006128   0.000000   0.006128 (  0.006139)

Benchmark.bm do |x|
  x.report do
    (1..100_000).each do |_i|
      with_splat(1, 2, 3)
    end
  end
end

# user     system      total        real
# 0.015717   0.000000   0.015717 (  0.015867)