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(* Title: LCF/ex.ML
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ID: $Id$
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Author: Tobias Nipkow
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Copyright 1991 University of Cambridge
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Some examples from Lawrence Paulson's book Logic and Computation.
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*)
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LCF_build_completed; (*Cause examples to fail if LCF did*)
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proof_timing := true;
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(*** Section 10.4 ***)
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val ex_thy = extend_theory thy "Ex 10.4"
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203
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([], [], [], [], [],
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[(["P"], "'a => tr"),
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(["G","H"], "'a => 'a"),
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(["K"], "('a => 'a) => ('a => 'a)")
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],
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None)
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[ ("P_strict", "P(UU) = UU"),
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("K", "K = (%h x. P(x) => x | h(h(G(x))))"),
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("H", "H = FIX(K)")
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];
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val ax = get_axiom ex_thy;
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val P_strict = ax"P_strict";
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val K = ax"K";
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val H = ax"H";
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val ex_ss = LCF_ss addsimps [P_strict,K];
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val H_unfold = prove_goal ex_thy "H = K(H)"
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(fn _ => [stac H 1, rtac (FIX_eq RS sym) 1]);
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val H_strict = prove_goal ex_thy "H(UU)=UU"
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(fn _ => [stac H_unfold 1, simp_tac ex_ss 1]);
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val ex_ss = ex_ss addsimps [H_strict];
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goal ex_thy "ALL x. H(FIX(K,x)) = FIX(K,x)";
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by(induct_tac "K" 1);
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by(simp_tac ex_ss 1);
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by(simp_tac (ex_ss setloop (split_tac [COND_cases_iff])) 1);
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by(strip_tac 1);
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by(stac H_unfold 1);
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by(asm_simp_tac ex_ss 1);
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val H_idemp_lemma = topthm();
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val H_idemp = rewrite_rule [mk_meta_eq (H RS sym)] H_idemp_lemma;
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(*** Example 3.8 ***)
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val ex_thy = extend_theory thy "Ex 3.8"
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([], [], [], [], [],
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[(["P"], "'a => tr"),
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(["F","G"], "'a => 'a"),
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(["H"], "'a => 'b => 'b"),
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(["K"], "('a => 'b => 'b) => ('a => 'b => 'b)")
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],
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None)
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[ ("F_strict", "F(UU) = UU"),
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("K", "K = (%h x y. P(x) => y | F(h(G(x),y)))"),
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("H", "H = FIX(K)")
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];
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val ax = get_axiom ex_thy;
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val F_strict = ax"F_strict";
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val K = ax"K";
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val H = ax"H";
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val ex_ss = LCF_ss addsimps [F_strict,K];
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goal ex_thy "ALL x. F(H(x::'a,y::'b)) = H(x,F(y))";
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by(stac H 1);
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by(induct_tac "K::('a=>'b=>'b)=>('a=>'b=>'b)" 1);
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by(simp_tac ex_ss 1);
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by(asm_simp_tac (ex_ss setloop (split_tac [COND_cases_iff])) 1);
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result();
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(*** Addition with fixpoint of successor ***)
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val ex_thy = extend_theory thy "fix ex"
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([], [], [], [], [],
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[(["s"], "'a => 'a"),
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(["p"], "'a => 'a => 'a")
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],
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None)
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[ ("p_strict", "p(UU) = UU"),
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("p_s", "p(s(x),y) = s(p(x,y))")
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];
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val ax = get_axiom ex_thy;
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val p_strict = ax"p_strict";
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val p_s = ax"p_s";
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val ex_ss = LCF_ss addsimps [p_strict,p_s];
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goal ex_thy "p(FIX(s),y) = FIX(s)";
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by(induct_tac "s" 1);
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by(simp_tac ex_ss 1);
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by(simp_tac ex_ss 1);
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result();
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(*** Prefixpoints ***)
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val asms = goal thy "[| f(p) << p; !!q. f(q) << q ==> p << q |] ==> FIX(f)=p";
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by(rewtac eq_def);
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by (rtac conjI 1);
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by(induct_tac "f" 1);
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by (rtac minimal 1);
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by(strip_tac 1);
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by (rtac less_trans 1);
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by (resolve_tac asms 2);
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by (etac less_ap_term 1);
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by (resolve_tac asms 1);
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by (rtac (FIX_eq RS eq_imp_less1) 1);
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result();
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maketest"END: file for LCF examples";
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