fun.rb - functional Ruby, taking some ideas from Clojure

fun.rb

class Hash
  def to_proc
    lambda { |x| self[x] }
  end
end

class Array
  def to_proc
    lambda { |x| self[x] }
  end
end

def get(key)
  lambda { |x| x[key] } 
end

def fib(n)
  @fibs ||= {}
  if @fibs[n] then @fibs[n]
  else
    f = if n < 0 then raise "n must be greater or equal to 0"
        elsif n <= 1 then n
        else
          fib(n - 2) + fib(n - 1)
        end
    @fibs[n] = f
    f
  end
end

fibs = (0..10).map(&method(:fib))

p [0, 8, 5, 2].map(&fibs)

p [{a: 1, b: 2}].map(&get(:a))

p [:a, :b].map(&{a: 1, b: 2})

p [0, 1, 2, 3, 4].map(&[:a, :b, :c, :d, :e])

def test(&blk)
  blk.call(0)
end

p test(&[:a, :b])

# Method / Proc combinitors
# =========================
#
# `chain`
# -------
#     
#    [].method(:last).then(:nil?)
#
#    [].method(:last) << &:nil
#    
#    [].map(&(&:last << &:nil?))
# 
# equivalent to
#
#    [].last.nil?
#
#    [].map { |x| x.last.nil? }
#
# 
# `compose`
# =========
#
#