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␈↓ α∧␈↓␈↓ αTA␈αLISP␈αpredicate␈α␈↓↓term␈↓␈αis␈αcalled␈αa␈αtermination␈αtester␈αif␈αfor␈αany␈αS-expression␈α␈↓↓e␈↓,␈α␈↓↓term[e]␈↓␈α=␈αT
␈↓ α∧␈↓if␈αand␈αonly␈αif␈αthe␈αLISP␈αevaluation␈αof␈α␈↓↓e␈↓␈αterminates;␈αotherwise␈α␈↓↓term[e]␈↓␈α=␈αF␈αor␈αis␈αundefined.␈α Thus
␈↓ α∧␈↓we␈αmust␈αhave␈α␈↓↓term[␈↓(CAR␈α(QUOTE␈α(A)))]␈α=␈αT,␈αand␈α␈↓↓term[␈↓((LABEL␈αFOO␈α(LAMBDA␈α(X)␈α(FOO
␈↓ α∧␈↓X)))␈α∀NIL)]␈α∀may␈α∀have␈α∀the␈α∀value␈α∀F␈α∃or␈α∀may␈α∀be␈α∀undefined.␈α∀ Let␈α∀␈↓↓term*␈↓␈α∀be␈α∃the␈α∀S-expression
␈↓ α∧␈↓representation of ␈↓↓term␈↓.

␈↓ α∧␈↓␈↓ αTWrite␈αa␈αLISP␈αfunction␈α
␈↓↓bad␈↓␈αsuch␈αthat␈αfor␈αany␈α
termination␈αtester␈α␈↓↓term␈↓,␈α␈↓↓bad[term*]␈↓␈αis␈α
defined,
␈↓ α∧␈↓but ␈↓↓term[bad[term*]]␈↓ is undefined.  Show that your ␈↓↓bad␈↓ works.

␈↓ α∧␈↓Hint:␈α∪A␈α∪one␈α∩line␈α∪answer␈α∪is␈α∪possible␈α∩using␈α∪␈↓↓subst␈↓␈α∪and␈α∩the␈α∪function␈α∪␈↓↓quine[x]␈α∪=␈α∩subst[x,␈↓X,(X
␈↓ α∧␈↓(QUOTE X))].






































␈↓ α∧␈↓␈↓ ε|1␈↓ ∧