frk.ru

def frk a, r, b
  lambda do |x|                                                                 
    r.call(a.call(x), b.call(x))
  end 
end

def sum a
  a.reduce(0) do |sum, value|
   sum + value
  end 
end
sum = method :sum

def cnt a
  a.length
end
cnt = method :cnt

def div a, b
  a/b 
end 
div = method :div

avg = frk sum, div, cnt 
ans = avg.call [1.0, 2.0, 3.0, 4.0]