compute histogram in ruby

gistfile1.rb

def tally inp; hash = Hash.new(0); inp.each {|k,v| hash[k] +=v}; hash; end
def histogram inp; hash = Hash.new(0); inp.each {|v| hash[v]+=1}; hash; end
def histogram2 inp; Hash[*inp.group_by{ |v| v }.flat_map{ |k, v| [k, v.size] }] end

def test_tally
  tally([['a',1],['b',1],['a',1],['c',1],['a',3], ['c',1]]) == {'a'=>5, 'b'=>1, 'c'=>2}
end

def test_histogram
  histogram(['a','b','a','c','a', 'c']) == {'a'=>3, 'b'=>1, 'c'=>2}
end

def test_histogram2
  histogram2(['a','b','a','c','a', 'c']) == {'a'=>3, 'b'=>1, 'c'=>2}
end

puts "Tally %s" % test_tally
puts "Hist %s" % test_histogram
puts "Hist2 %s" % test_histogram2