gistfile1.rbx

# see http://pastie.org/274816 and http://pastie.org/274829
# I have: "foo"
# I need: ['f', 'fo', 'foo']

require 'benchmark'

def using_split(str)
  str.split(//mu).inject([]) do |arr, char|
     arr << arr[-1].to_s + char.to_s
  end
end

def using_map(str)
  (1..str.length).map do |i|
    str[0, i]
  end
end

def using_upto(str)
  result = []
  1.upto(str.length) do |i|
    result << str[0, i]
  end
  result
end

def using_times(str)
  result = []
  i = 1
  str.length.times do 
    result << str[0, i]
    i += 1
  end
  result
end

def using_for(str)
  result = []
  for i in 1..str.length
    result << str[0, i]
  end
  result
end

puts "using_split: " + using_split("foo").inspect
puts "using_map:   " + using_map("foo").inspect
puts "using_upto:  " + using_upto("foo").inspect
puts "using_times: " + using_times("foo").inspect
puts "using_for:   " + using_for("foo").inspect

Benchmark.bm(100000) do |x|
  x.report { using_split("foo") }
  x.report { using_map("foo") }
  x.report { using_upto("foo") }
  x.report { using_times("foo") }
  x.report { using_for("foo") }
end

output.txt

using_split: ["f", "fo", "foo"]
using_map:   ["f", "fo", "foo"]
using_upto:  ["f", "fo", "foo"]
using_times: ["f", "fo", "foo"]
using_for:   ["f", "fo", "foo"]

user     system      total        real
0.000000   0.000000   0.000000 (  0.000033)
0.000000   0.000000   0.000000 (  0.000031)
0.000000   0.000000   0.000000 (  0.000019)
0.000000   0.000000   0.000000 (  0.000021)
0.000000   0.000000   0.000000 (  0.000029)