src/HOL/ex/Puzzle.ML
 author clasohm Wed, 22 Mar 1995 12:42:34 +0100 changeset 969 b051e2fc2e34 child 1266 3ae9fe3c0f68 permissions -rw-r--r--
converted ex with curried function application

(*  Title: 	HOL/ex/puzzle.ML
ID:         \$Id\$
Author: 	Tobias Nipkow

For puzzle.thy.  A question from "Bundeswettbewerb Mathematik"

Proof due to Herbert Ehler
*)

(*specialized form of induction needed below*)
val prems = goal Nat.thy "[| P(0); !!n. P(Suc(n)) |] ==> !n.P(n)";
by (EVERY1 [rtac (nat_induct RS allI), resolve_tac prems, resolve_tac prems]);
qed "nat_exh";

goal Puzzle.thy "! n. k=f(n) --> n <= f(n)";
by (res_inst_tac [("n","k")] less_induct 1);
by (rtac nat_exh 1);
by (simp_tac nat_ss 1);
by (rtac impI 1);
by (rtac classical 1);
by (dtac not_leE 1);
by (subgoal_tac "f(na) <= f(f(na))" 1);
by (best_tac (HOL_cs addIs [lessD,Puzzle.f_ax,le_less_trans,le_trans]) 1);
by (fast_tac (HOL_cs addIs [Puzzle.f_ax]) 1);
bind_thm("lemma", result() RS spec RS mp);

goal Puzzle.thy "n <= f(n)";
by (fast_tac (HOL_cs addIs [lemma]) 1);
qed "lemma1";

goal Puzzle.thy "f(n) < f(Suc(n))";
by (fast_tac (HOL_cs addIs [Puzzle.f_ax,le_less_trans,lemma1]) 1);
qed "lemma2";

val prems = goal Puzzle.thy "(!!n.f(n) <= f(Suc(n))) ==> m<n --> f(m) <= f(n)";
by (res_inst_tac[("n","n")]nat_induct 1);
by (simp_tac nat_ss 1);
by (simp_tac nat_ss 1);
by (fast_tac (HOL_cs addIs (le_trans::prems)) 1);
bind_thm("mono_lemma1", result() RS mp);

val [p1,p2] = goal Puzzle.thy
"[| !! n. f(n)<=f(Suc(n));  m<=n |] ==> f(m) <= f(n)";
by (rtac (p2 RS le_imp_less_or_eq RS disjE) 1);
by (etac (p1 RS mono_lemma1) 1);
by (fast_tac (HOL_cs addIs [le_refl]) 1);
qed "mono_lemma";

val prems = goal Puzzle.thy "m <= n ==> f(m) <= f(n)";
by (fast_tac (HOL_cs addIs ([mono_lemma,less_imp_le,lemma2]@prems)) 1);
qed "f_mono";

goal Puzzle.thy "f(n) = n";
by (rtac le_anti_sym 1);
by (rtac lemma1 2);