recovered a version of dequeue_towards (cf. bb7b5a5942c7);
join_results: work only towards explicit dependencies -- otherwise could produce dynamic cycle (not recorded in queue);
theory FP0 imports PreList begin
datatype 'a list = Nil ("[]")
| Cons 'a "'a list" (infixr "#" 65)
consts app :: "'a list \<Rightarrow> 'a list \<Rightarrow> 'a list" (infixr "@" 65)
rev :: "'a list \<Rightarrow> 'a list"
primrec
"[] @ ys = ys"
"(x # xs) @ ys = x # (xs @ ys)"
primrec
"rev [] = []"
"rev (x # xs) = (rev xs) @ (x # [])"
theorem rev_rev [simp]: "rev(rev xs) = xs"
(*<*)oops(*>*)text_raw{*\isanewline\isanewline*}
end