# HG changeset patch
# User boehmes
# Date 1235556463 -3600
# Node ID c06885c3657527a93c250b365cc0813335990f57
# Parent  5aa3140ad52e624123769d5494bf00c94f6553be
Polished conversion section.

diff -r 5aa3140ad52e -r c06885c36575 CookBook/Tactical.thy
--- a/CookBook/Tactical.thy	Wed Feb 25 10:14:42 2009 +0100
+++ b/CookBook/Tactical.thy	Wed Feb 25 11:07:43 2009 +0100
@@ -1,5 +1,6 @@
 theory Tactical
 imports Base FirstSteps
+uses "infix_conv.ML"
 begin
 
 chapter {* Tactical Reasoning\label{chp:tactical} *}
@@ -1317,40 +1318,55 @@
 section {* Conversions\label{sec:conversion} *}
 
 text {*
-Conversions are meta-equalities depending on some input term. There type is
+Conversions are meta-equalities depending on some input term. Their type is
 as follows:
 *}
 
 ML {*type conv = Thm.cterm -> Thm.thm*}
 
 text {*
-The simplest two conversions are @{ML "Conv.all_conv"} and @{ML "Conv.no_conv"}:
+The simplest two conversions are @{ML "Conv.all_conv"}, which maps a term to an instance of the reflexivity theorem, and @{ML "Conv.no_conv"}, which always fails:
 
 @{ML_response_fake "Conv.all_conv @{cterm True}" "True \<equiv> True"}
 
 @{ML_response_fake "Conv.no_conv @{cterm True}" "*** Exception- CTERM (\"no conversion\", []) raised"}
 
-Further basic conversions are, for example, @{ML "Thm.beta_conversion"} and
- @{ML "Conv.rewr_conv"}:
+A further basic conversion is, for example, @{ML "Thm.beta_conversion"}:
+
+@{ML_response_fake "Thm.beta_conversion true @{cterm \"(\<lambda>x. x \<or> False) True\"}"
+"(\<lambda>x. x \<or> False) True \<equiv> True \<or> False"}
+
+User-defined rewrite rules can be applied by the conversion
+@{ML "Conv.rewr_conv"}. Consider, for example, the following rule:
 *}
 
 lemma true_conj1: "True \<and> P \<equiv> P" by simp
 
 text {*
-@{ML_response_fake "Thm.beta_conversion true @{cterm \"(\<lambda>x. x \<or> False) True\"}"
-"(\<lambda>x. x \<or> False) True \<equiv> True \<or> False"}
+Here is how this rule can be used for rewriting:
 
 @{ML_response_fake "Conv.rewr_conv @{thm true_conj1} @{cterm \"True \<or> False\"}"
  "True \<and> False \<equiv> False"}
+*}
 
+text {*
 Basic conversions can be combined with a number of conversionals, i.e.
 conversion combinators:
 
-@{ML_response_fake "Conv.then_conv (Thm.beta_conversion true, Conv.rewr_conv @{thm true_conj1}) @{cterm \"(\<lambda>x. x \<and> False) True\"}" "(\<lambda>x. x \<and> False) True \<equiv> False"}
+@{ML_response_fake
+"(Thm.beta_conversion true then_conv Conv.rewr_conv @{thm true_conj1})
+  @{cterm \"(\<lambda>x. x \<and> False) True\"}"
+"(\<lambda>x. x \<and> False) True \<equiv> False"}
 
-@{ML_response_fake "Conv.else_conv (Conv.rewr_conv @{thm true_conj1}, Conv.all_conv) @{cterm \"P \<or> (True \<and> Q)\"}" "P \<or> (True \<and> Q) \<equiv> P \<or> (True \<and> Q)"}
+@{ML_response_fake
+"(Conv.rewr_conv @{thm true_conj1} else_conv Conv.all_conv)
+  @{cterm \"P \<or> (True \<and> Q)\"}"
+"P \<or> (True \<and> Q) \<equiv> P \<or> (True \<and> Q)"}
 
-@{ML_response_fake "Conv.arg_conv (Conv.rewr_conv @{thm true_conj1}) @{cterm \"P \<or> (True \<and> Q)\"}" "P \<or> (True \<and> Q) \<equiv> P \<or> Q"}
+@{ML_response_fake
+"Conv.arg_conv (Conv.rewr_conv @{thm true_conj1})
+  @{cterm \"P \<or> (True \<and> Q)\"}"
+"P \<or> (True \<and> Q) \<equiv> P \<or> Q"}
 
 \begin{readmore}
 See @{ML_file "Pure/conv.ML"} for more conversionals. Further basic conversions
@@ -1362,70 +1378,86 @@
 be seen as a controllable, bare-bone version of Isabelle's simplifier. We
 will demonstrate this feature in the following example.
 
-For the moment, let's assumes we want to simplify according to the rewrite rule
-@{thm true_conj1}. As a conversion, this may look as follows:
+To begin with, let's assumes we want to simplify with the rewrite rule
+@{text true_conj1}. As a conversion, this may look as follows:
 *}
 
 ML {*fun all_true1_conv ctxt ct =
   (case Thm.term_of ct of
-    @{term "op \<and>"} $ @{term True} $ _ => Conv.rewr_conv @{thm true_conj1} ct
-  | _ $ _ => Conv.combination_conv (all_true1_conv ctxt) (all_true1_conv ctxt) ct
+    @{term "op \<and>"} $ @{term True} $ _ => 
+      (Conv.arg_conv (all_true1_conv ctxt) then_conv
+        Conv.rewr_conv @{thm true_conj1}) ct
+  | _ $ _ => Conv.combination_conv (all_true1_conv ctxt)
+      (all_true1_conv ctxt) ct
   | Abs _ => Conv.abs_conv (fn (_, cx) => all_true1_conv cx) ctxt ct
   | _ => Conv.all_conv ct)*}
 
 text {*
-Here is the new conversion in action:
+Here is this conversion in action:
 
-@{ML_response_fake "all_true1_conv @{context} @{cterm \"distinct [1, x] \<longrightarrow> True \<and> 1 \<noteq> x\"}"
-  "distinct [1, x] \<longrightarrow> True \<and> 1 \<noteq> x \<equiv> distinct [1, x] \<longrightarrow> 1 \<noteq> x"}
+@{ML_response_fake
+"all_true1_conv @{context}
+  @{cterm \"distinct [1, x] \<longrightarrow> True \<and> 1 \<noteq> x\"}"
+"distinct [1, x] \<longrightarrow> True \<and> 1 \<noteq> x \<equiv> distinct [1, x] \<longrightarrow> 1 \<noteq> x"}
 
-Now, let's complicate the task: Rewrite according to the rule
-@{thm true_conj1}, but only in the first arguments of @{term If}:
+Now, let's complicate the task a bit: Rewrite according to the rule
+@{text true_conj1}, but only in the first arguments of @{term If}:
 *}
 
 ML {*fun if_true1_conv ctxt ct =
   (case Thm.term_of ct of
-    Const (@{const_name If}, _) $ _ => Conv.arg_conv (all_true1_conv ctxt) ct
-  | _ $ _ => Conv.combination_conv (if_true1_conv ctxt) (if_true1_conv ctxt) ct
+    Const (@{const_name If}, _) $ _ =>
+      Conv.arg_conv (all_true1_conv ctxt) ct
+  | _ $ _ => Conv.combination_conv (if_true1_conv ctxt)
+      (if_true1_conv ctxt) ct
   | Abs _ => Conv.abs_conv (fn (_, cx) => if_true1_conv cx) ctxt ct
   | _ => Conv.all_conv ct)*}
 
 text {*
-Here is an application of this new conversion:
+Here is an application of this conversion:
 
-@{ML_response_fake "if_true1_conv @{context} @{cterm \"if P (True \<and> 1 \<noteq> 2) then True \<and> True else True \<and> False\"}" "if P (True \<and> 1 \<noteq> 2) then True \<and> True else True \<and> False \<equiv> if P (1 \<noteq> 2) then True \<and> True else True \<and> False"}
+@{ML_response_fake
+"if_true1_conv @{context}
+  @{cterm \"if P (True \<and> 1 \<noteq> 2) then True \<and> True else True \<and> False\"}"
+"if P (True \<and> 1 \<noteq> 2) then True \<and> True else True \<and> False \<equiv> if P (1 \<noteq> 2) then True \<and> True else True \<and> False"}
 *}
 
 text {*
 Conversions can also be turned into a tactic with the @{ML CONVERSION}
-tactical, and there are predefined conversionals to traverse a goal state
-
-@{term "\<And>x. P \<Longrightarrow> Q"}: 
-
-The conversional
-@{ML Conv.params_conv} applies a conversion to @{term "P \<Longrightarrow> Q"},
-@{ML Conv.prems_conv} applies a conversion to all premises in @{term "P \<Longrightarrow> Q"}, and
-@{ML Conv.concl_conv} applies a conversion to the conclusion @{term Q} in @{term "P \<Longrightarrow> Q"}.
+tactical, and there are predefined conversionals to traverse a goal state.
+Given a state @{term "\<And>x. P \<Longrightarrow> Q"},  the conversional
+@{ML Conv.params_conv} applies a conversion to @{term "P \<Longrightarrow> Q"};
+given a state @{term "\<lbrakk> P1; P2 \<rbrakk> \<Longrightarrow> Q"},
+the conversional @{ML Conv.prems_conv} applies a conversion to the premises
+@{term P1} and @{term P2}, and @{ML Conv.concl_conv} applies a conversion to
+the conclusion @{term Q}.
 
 Assume we want to apply @{ML all_true1_conv} only in the conclusion
 of the goal, and @{ML if_true1_conv} should only be applied in the premises.
 Here is a tactic doing exactly that:
 *}
 
-ML {*local open Conv 
-in
-val true1_tac = CSUBGOAL (fn (goal, i) =>
+ML {*val true1_tac = CSUBGOAL (fn (goal, i) =>
   let val ctxt = ProofContext.init (Thm.theory_of_cterm goal)
   in
     CONVERSION (
       Conv.params_conv ~1 (fn cx =>
         (Conv.prems_conv ~1 (if_true1_conv cx)) then_conv
-          (Conv.concl_conv ~1 (all_true1_conv cx))) ctxt) i
-  end)
-end*}
+          Conv.concl_conv ~1 (all_true1_conv cx)) ctxt) i
+  end)*}
+
+text {* 
+To demonstrate this tactic, consider the following example:
+*}
 
-text {* FIXME: give example, show that the conditional rewriting works *}
-
+lemma
+  "if True \<and> P then P else True \<and> False \<Longrightarrow>
+  (if True \<and> Q then Q else P) \<longrightarrow> True \<and> (True \<and> Q)"
+apply(tactic {* true1_tac 1 *})
+txt {* \begin{minipage}{\textwidth}
+       @{subgoals [display]} 
+       \end{minipage} *}
+(*<*)oops(*>*)
 
 text {*
 Conversions are not restricted to work on certified terms only, they can also
@@ -1433,7 +1465,9 @@
 theorem, by the help of @{ML Conv.fconv_rule}. As an example, consider the
 conversion @{ML all_true1_conv} again:
 
-@{ML_response_fake "Conv.fconv_rule (all_true1_conv @{context}) @{lemma \"P \<or> (True \<and> \<not>P)\" by simp}" "P \<or> \<not>P"}
+@{ML_response_fake
+"Conv.fconv_rule (all_true1_conv @{context})
+  @{lemma \"P \<or> (True \<and> \<not>P)\" by simp}" "P \<or> \<not>P"}
 *}
 
 
diff -r 5aa3140ad52e -r c06885c36575 CookBook/infix_conv.ML
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/CookBook/infix_conv.ML	Wed Feb 25 11:07:43 2009 +0100
@@ -0,0 +1,9 @@
+signature INFIX_CONV =
+sig
+  val then_conv : Thm.conv * Thm.conv -> Thm.conv
+  val else_conv : Thm.conv * Thm.conv -> Thm.conv
+end
+
+structure InfixConv : INFIX_CONV = Conv
+
+open InfixConv
diff -r 5aa3140ad52e -r c06885c36575 cookbook.pdf
Binary file cookbook.pdf has changed