(require 'grass)
(grass-plant-code
 '(
   (abs print (n)
	((app n succ . n_succ)
	 (app n_succ w . ch)
	 (app out ch)
	 ))
   (abs id (n)
	())
   (abs mkidprint (f n)
	((app print n)
	 (app id f)
	 ))
   (abs W (x y)
	((app x x . xx)
	 (app xx y)     ;; W = λxy.xxy
	 ))
   (abs X (f x)
	((app W x . Wx) ;; (λxy.xxy)x -> λy.xxy
	 (app f Wx)     ;; X = λfx.f(λy.xxy)
	 ))
   (abs Y (f) ;; Y combinator
	((app X f . Xf) ;; (λfx.f(λy.xxy))f -> λx.f(λy.xxy)
	 (app Xf Xf)    ;; Y = λf.(λx.f(λy.xxy))(λx.f(λy.xxy))
	 ))
   (abs idprint (n)
	((app Y mkidprint . Y_mkidprint)
	 (app Y_mkidprint n)
	 ))
   (abs <2> (f x)
	((app f x . fx)
	 (app f fx) ;; f (f x)
	 ))
   (app <2> <2> . <4>) ;; 2^2 = 4
   (abs inc (n f x)
	((app n f . nf)
	 (app nf x . nfx)
	 (app f nfx) ;; f (n f x)
	 ))
   (app inc <2> . <3>)
   (app <2> <3> . <9>) ;; 3^2 = 9
   (app <4> inc . <4>inc)
   (app <4>inc <9> . <13>)
   (app inc <13> . <14>)
   (app inc <14> . <15>)
   (abs <2> (f x)
	((app f x . fx)
	 (app f fx) ;; f (f x)
	 ))
   (app <2> <15> . <225>) ;; 15^2 = 225
   (app <2> <14> . <196>) ;; 14^2 = 196
   (app <2> <13> . <169>) ;; 13^2 = 169 ; SPC
   (app <3> <4>inc . <12>inc)
   (app <12>inc <169> . <181>) ;; ,
   (app <12>inc <196> . <208>)
   (app <12>inc <225> . <237>) ;; d
   (abs inc (n f x)
	((app n f . nf)
	 (app nf x . nfx)
	 (app f nfx) ;; f (n f x)
	 ))
   (app inc <169> . <170>) ;; !
   (app inc <208> . <209>) ;; H
   (app inc <237> . <238>) ;; e
   (app inc <238> . <239>)
   (app <3> inc . <3>inc)
   (app <3>inc <239> . <242>)
   (app <3>inc <242> . <245>) ;; l
   (app <3>inc <245> . <248>) ;; o
   (app <3>inc <248> . <251>) ;; r
   (abs print_Hello (dummy)
	((app idprint <209>) ;; H
	 (app 1 <238>) ;; e
	 (app 1 <245>) ;; l
	 (app 1 <245>) ;; l
	 (app 1 <248>) ;; o
	 (app 1 <181>) ;; ,
	 (app 1 <169>) ;; SPC
	 ))
   (abs <0> (f x) ;; w
	())
   (app print_Hello 1) ;; (1 is dummy argument)
   (app 1 <0>)   ;; w
   (app 1 <248>) ;; o
   (app 1 <251>) ;; r
   (app 1 <245>) ;; l
   (app 1 <237>) ;; d
   (app 1 <170>) ;; !
   (abs main (n)
	()) ;; (Null function to avoid error)
   ))