# -*- ruby -*-
# recursive iterator and recursive block

class Object
  CALL_STACK__ = []

  def save_call(sym, *args, &block)
    CALL_STACK__.push([sym,args,block])
    begin
      resp = __send__(sym,*args,&block)
    ensure
      CALL_STACK__.pop
    end
    return resp
  end

  def save_block(sym, rsyms, *args, &block)
    obj = __send__(sym,*args,&block)
    rsyms.each{|rsym|
      obj.instance_eval [
	"alias _#{rsym}_ #{rsym}",
	"def #{rsym}(*args)",
	"  CALL_STACK__.push([nil,nil,self])",
	"  begin",
	"    resp = _#{rsym}_(*args)",
	"  ensure",
	"    CALL_STACK__.pop",
	"  end",
	"  resp",
	"end",
      ].join("\n")
    }
    obj
  end

  def restore_block()
    CALL_STACK__[-1][2]
  end

  def restore_call()
    __send__(CALL_STACK__[-1][0],
	     *(CALL_STACK__[-1][1]),
	     &(CALL_STACK__[-1][2]))
  end

  alias recursive save_call
  alias recurse restore_call

  def y_comb(sym,*args,&block)
    u  = proc{|f| f[f]}
    u1 = proc{|f| __send__(sym,*args){|*x| yield(f[f]).call(*x)}}
    u[u1]
  end

  alias pass_block y_comb
end

if( __FILE__ == $0 )

ary = [1,2,[31,32],[41,42,[431,432]]]

print("recursive --\n")
ary.recursive(:each){|elem|
  case elem
  when Array
    elem.recurse
  else
    p elem
  end
}

print("fact --\n")
fact = Proc.y_comb(:new){|cb| proc{|n|
  if( n > 1 )
    n * cb.call(n-1)
  else
    n
  end
}}
p fact.call(3)

print("sum --\n")
sum = Proc.y_comb(:new){|cb| proc{|n|
  if( n > 0 )
    n + cb.call(n-1)
  else
    n
  end
}}
p sum.call(10)

end