[[[[pop null] popd succ                          ] 
  [[null]     pop pred 1 ack1                    ] 
              [[dup pred swap] dip pred ack1 ack1]] cond] 		`ack1	def;


[[[m n][[[m null] n succ                     ]
        [[n null] m pred 1 ack2              ] 
         	  [m pred m n pred ack2 ack2]] cond] let]		`ack2	def;

[[[[pop null]                 [popd succ]    ] 
  [[null]                     [pop pred 1] []] 
  [[[dup pred swap] dip pred] []           []]] condnestrec] 		`ack3	def;

[[[[[[m n]m null]let]         	[[[m n]n succ]let]     ] 
  [[[[m n]n null]let]           [[[m n]m pred 1]let] []] 
  [[[[m n]m pred m n pred]let]  []           	     []]] condnestrec]	`ack4	def;