ex/qsort.ML

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(*  Title: 	HOL/ex/qsort.ML
    ID:         $Id$
    Author: 	Tobias Nipkow
    Copyright   1994 TU Muenchen

Two verifications of Quicksort
*)

val ss = sorting_ss addsimps ([Qsort.qsort_Nil,Qsort.qsort_Cons]@conj_comms);

goal Qsort.thy "!x. mset(qsort(le,xs),x) = mset(xs,x)";
by(res_inst_tac[("xs","xs"),("p","le")]Qsort.qsort_ind 1);
by(ALLGOALS(asm_simp_tac (ss setloop (split_tac [expand_if]))));
result();


goal Qsort.thy "(Alls x:[x:xs.P(x)].Q(x)) = (Alls x:xs. P(x)-->Q(x))";
by(list_ind_tac "xs" 1);
by(ALLGOALS(asm_simp_tac (ss setloop (split_tac [expand_if]))));
val ss = ss addsimps [result()];

goal Qsort.thy
 "((Alls x:xs.P(x)) & (Alls x:xs.Q(x))) = (Alls x:xs. P(x)&Q(x))";
by(list_ind_tac "xs" 1);
by(ALLGOALS(asm_simp_tac ss));
val ss = ss addsimps [result()];

goal HOL.thy "((~P --> Q) & (P --> Q)) = Q";
by(fast_tac HOL_cs 1);
val lemma = result();

goal Qsort.thy "(Alls x:qsort(le,xs).P(x))  =  (Alls x:xs.P(x))";
by(res_inst_tac[("xs","xs"),("p","le")]Qsort.qsort_ind 1);
by(ALLGOALS(asm_simp_tac (ss addsimps [lemma])));
val ss = ss addsimps [result()];

goal Qsort.thy
 "sorted(le,xs@ys) = (sorted(le,xs) & sorted(le,ys) & \
\                     (Alls x:xs. Alls y:ys. le(x,y)))";
by(list_ind_tac "xs" 1);
by(ALLGOALS(asm_simp_tac ss));
val ss = ss addsimps [result()];

goal Qsort.thy 
 "!!le. [| total(le); transf(le) |] ==>  sorted(le,qsort(le,xs))";
by(res_inst_tac[("xs","xs"),("p","le")]Qsort.qsort_ind 1);
by(ALLGOALS(asm_full_simp_tac (ss addsimps [list_all_mem_conv]) ));
by(rewrite_goals_tac [Sorting.total_def,Sorting.transf_def]);
by(fast_tac HOL_cs 1);
result();


(* A verification based on predicate calculus rather than combinators *)

val sorted_Cons =
  rewrite_rule [list_all_mem_conv RS eq_reflection] Sorting.sorted_Cons;

val ss = list_ss addsimps
 [Sorting.sorted_Nil,sorted_Cons,
  Qsort.qsort_Nil,Qsort.qsort_Cons];


goal Qsort.thy "x mem qsort(le,xs)  =  x mem xs";
by(res_inst_tac[("xs","xs"),("p","le")]Qsort.qsort_ind 1);
by(ALLGOALS(asm_simp_tac (ss setloop (split_tac [expand_if]))));
by(fast_tac HOL_cs 1);
val ss = ss addsimps [result()];

goal Qsort.thy
 "sorted(le,xs@ys) = (sorted(le,xs) & sorted(le,ys) & \
\                     (!x. x mem xs --> (!y. y mem ys --> le(x,y))))";
by(list_ind_tac "xs" 1);
by(ALLGOALS(asm_simp_tac (ss setloop (split_tac [expand_if]))));
by(fast_tac HOL_cs 1);
val ss = ss addsimps [result()];

goal Qsort.thy
  "!!xs. [| total(le); transf(le) |] ==>  sorted(le,qsort(le,xs))";
by(res_inst_tac[("xs","xs"),("p","le")]Qsort.qsort_ind 1);
by(simp_tac ss 1);
by(asm_full_simp_tac (ss setloop (split_tac [expand_if])) 1);
by(rewrite_goals_tac [Sorting.total_def,Sorting.transf_def]);
by(fast_tac HOL_cs 1);
result();