gistfile1.rb

module Functional

  module_function

  def unary
    ->(a,*b){ a}
  end
  
  def binary
    ->(a,b,*c){ [a,b]}
  end

  def variadic(fn)    
    
    ->(*args){
      required_args = (0 < fn.arity) ? fn.arity : (fn.arity.abs) - 1
      one_less_index = required_args -2
      rest_index = one_less_index + 1      
      ordinary =  (0  <= one_less_index) ? args[0..one_less_index] : []
      rest = args[rest_index..-1]
      args = required_args <= args.length ? ordinary + [rest]: []
      
      fn.call(*args)
    }
  end
  
  def apply_first(fn,first)
    ->(*args){
      fn.call(*([first] + args))
    }
  end

  def apply_last(fn,last)
     ->(*args){
         fn.call( *( args + [last]) )
         }
  end
end