(letrec check(comment quote((Variable definition and scope checker)(P Henderson
and S B Jones PRG Oxford August 1982)))(check lambda(p)(checkexpr p(quote
NIL)(quote NIL)))(checkexpr lambda(p e loc)(if(atom p)(ok p e loc)(if(eq
(head p)(quote quote))(quote NIL)(if(eq(head p)(quote lambda))(checkexpr
(head(tail(tail p)))(append(head(tail p))e)loc)(if(eq(head p)(quote let
))(checklet(tail p)e loc)(if(eq(head p)(quote letrec))(checkletrec(tail
p)e loc)(if(isop(head p))(checkeach(tail p)e loc)(checkeach p e loc))))
))))(ok lambda(name e loc)(if(eq e(quote NIL))(cons(cons name loc)(quote
NIL))(if(eq name(head e))(quote NIL)(ok name(tail e)loc))))(isop lambda
(op)(member op(quote(chr atom head tail leq eq cons add sub mul div rem
if))))(member lambda(x l)(if(eq l(quote NIL))(quote F)(if(eq x(head l))
(quote T)(member x(tail l)))))(append lambda(l1 l2)(if(eq l1(quote NIL)
)l2(cons(head l1)(append(tail l1)l2))))(vars lambda(l)(if(eq l(quote NIL
))(quote NIL)(cons(head(head l))(vars(tail l)))))(checklet lambda(p e loc
)(append(checkexpr(head p)(append(vars(tail p))e)loc)(checklist(tail p)
e loc)))(checkletrec lambda(p e loc)(let(append(checkexpr(head p)newe loc
)(checklist(tail p)newe loc))(newe append(vars(tail p))e)))(checklist lambda
(l e loc)(if(eq l(quote NIL))(quote NIL)(append(checkexpr(tail(head l))
e(cons(head(head l))loc))(checklist(tail l)e loc))))(checkeach lambda(l
e loc)(if(eq l(quote NIL))(quote NIL)(append(checkexpr(head l)e loc)(checkeach
(tail l)e loc)))))