本当にどうでも良い話だが、かっこいいトレースが出来たのでコピペ。Joy のようですでに Joy で無くなりつつある自作言語の意味ツリーを S 式のような記法で出力してゆく様子。y:= はセッター、:y はゲッターでこの部分で Smalltalk と通信します。ツリーの中では副作用が起こらないので、いわば IO モナドの働きをします。
'acc' get 0.2 + dup 'y' get swap - 'y' set swap 'acc' set 10 'x' get + 'x' set > 'acc' :: get 0.2 + dup 'y' get swap - 'y' set swap 'acc' set 10 'x' get + 'x' set > :acc :: 0.2 + dup 'y' get swap - 'y' set swap 'acc' set 10 'x' get + 'x' set > :acc 0.2 :: + dup 'y' get swap - 'y' set swap 'acc' set 10 'x' get + 'x' set > (+ :acc 0.2 ) :: dup 'y' get swap - 'y' set swap 'acc' set 10 'x' get + 'x' set > (+ :acc 0.2 ) (+ :acc 0.2 ) :: 'y' get swap - 'y' set swap 'acc' set 10 'x' get + 'x' set > (+ :acc 0.2 ) (+ :acc 0.2 ) 'y' :: get swap - 'y' set swap 'acc' set 10 'x' get + 'x' set > (+ :acc 0.2 ) (+ :acc 0.2 ) :y :: swap - 'y' set swap 'acc' set 10 'x' get + 'x' set > (+ :acc 0.2 ) :y (+ :acc 0.2 ) :: - 'y' set swap 'acc' set 10 'x' get + 'x' set > (+ :acc 0.2 ) (- :y (+ :acc 0.2 ) ) :: 'y' set swap 'acc' set 10 'x' get + 'x' set > (+ :acc 0.2 ) (- :y (+ :acc 0.2 ) ) 'y' :: set swap 'acc' set 10 'x' get + 'x' set > (+ :acc 0.2 ) (y:= (- :y (+ :acc 0.2 ) )) :: swap 'acc' set 10 'x' get + 'x' set > (y:= (- :y (+ :acc 0.2 ) )) (+ :acc 0.2 ) :: 'acc' set 10 'x' get + 'x' set > (y:= (- :y (+ :acc 0.2 ) )) (+ :acc 0.2 ) 'acc' :: set 10 'x' get + 'x' set > (y:= (- :y (+ :acc 0.2 ) )) (acc:= (+ :acc 0.2 )) :: 10 'x' get + 'x' set > (y:= (- :y (+ :acc 0.2 ) )) (acc:= (+ :acc 0.2 )) 10 :: 'x' get + 'x' set > (y:= (- :y (+ :acc 0.2 ) )) (acc:= (+ :acc 0.2 )) 10 'x' :: get + 'x' set > (y:= (- :y (+ :acc 0.2 ) )) (acc:= (+ :acc 0.2 )) 10 :x :: + 'x' set > (y:= (- :y (+ :acc 0.2 ) )) (acc:= (+ :acc 0.2 )) (+ 10 :x ) :: 'x' set > (y:= (- :y (+ :acc 0.2 ) )) (acc:= (+ :acc 0.2 )) (+ 10 :x ) 'x' :: set > (y:= (- :y (+ :acc 0.2 ) )) (acc:= (+ :acc 0.2 )) (x:= (+ 10 :x )) ::
