merged
authorwenzelm
Sat, 13 Jun 2015 22:44:22 +0200
changeset 60460 abee0de69a89
parent 60442 310853646597 (current diff)
parent 60459 2761a2249c83 (diff)
child 60461 22995ec9fefd
child 60464 16bed2709b70
merged
NEWS
--- a/NEWS	Sat Jun 13 19:23:41 2015 +0100
+++ b/NEWS	Sat Jun 13 22:44:22 2015 +0200
@@ -24,13 +24,13 @@
     for x :: 'a and y :: 'a
     <proof>
 
-The local assumptions are always bound to the name "prems".  The result
-is exported from context of the statement as usual.  The above roughly
+The local assumptions are bound to the name "that". The result is
+exported from context of the statement as usual. The above roughly
 corresponds to a raw proof block like this:
 
   {
     fix x :: 'a and y :: 'a
-    assume prems: "A x" "B y"
+    assume that: "A x" "B y"
     have "C x y" <proof>
   }
   note result = this
@@ -38,6 +38,27 @@
 * New command 'supply' supports fact definitions during goal refinement
 ('apply' scripts).
 
+* New command 'consider' states rules for generalized elimination and
+case splitting. This is like a toplevel statement "theorem obtains" used
+within a proof body; or like a multi-branch 'obtain' without activation
+of the local context elements yet.
+
+* Proof method "cases" allows to specify the rule as first entry of
+chained facts.  This is particularly useful with 'consider':
+
+  consider (a) A | (b) B | (c) C <proof>
+  then have something
+  proof cases
+    case a
+    then show ?thesis <proof>
+  next
+    case b
+    then show ?thesis <proof>
+  next
+    case c
+    then show ?thesis <proof>
+  qed
+
 
 *** Pure ***
 
--- a/src/Doc/Isar_Ref/Proof.thy	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Doc/Isar_Ref/Proof.thy	Sat Jun 13 22:44:22 2015 +0200
@@ -435,21 +435,22 @@
      @@{command schematic_corollary}) (stmt | statement)
     ;
     (@@{command have} | @@{command show} | @@{command hence} | @@{command thus})
-      stmt if_prems @{syntax for_fixes}
+      stmt (@'if' stmt)? @{syntax for_fixes}
     ;
     @@{command print_statement} @{syntax modes}? @{syntax thmrefs}
     ;
   
     stmt: (@{syntax props} + @'and')
     ;
-    if_prems: (@'if' stmt)?
-    ;
     statement: @{syntax thmdecl}? (@{syntax_ref "includes"}?) (@{syntax context_elem} *) \<newline>
       conclusion
     ;
-    conclusion: @'shows' stmt | @'obtains' (@{syntax par_name}? obtain_case + '|')
+    conclusion: @'shows' stmt | @'obtains' @{syntax obtain_clauses}
     ;
-    obtain_case: (@{syntax vars} + @'and') @'where' (@{syntax thmdecl}? (@{syntax prop}+) + @'and')
+    @{syntax_def obtain_clauses}: (@{syntax par_name}? obtain_case + '|')
+    ;
+    @{syntax_def obtain_case}: (@{syntax vars} + @'and') @'where'
+      (@{syntax thmdecl}? (@{syntax prop}+) + @'and')
   \<close>}
 
   \begin{description}
@@ -523,11 +524,10 @@
   @{variable_ref "?thesis"}) to be bound automatically, see also
   \secref{sec:term-abbrev}.
 
-  The optional case names of @{element_ref "obtains"} have a twofold
-  meaning: (1) in the proof of this claim they refer to the local context
-  introductions, (2) in the resulting rule they become annotations for
-  symbolic case splits, e.g.\ for the @{method_ref cases} method
-  (\secref{sec:cases-induct}).
+  Structured goal statements involving @{keyword_ref "if"} define the
+  special fact ``@{text that}'' to refer to these assumptions in the proof
+  body. The user may provide separate names according to the syntax of the
+  statement.
 \<close>
 
 
@@ -853,15 +853,6 @@
 subsection \<open>Emulating tactic scripts \label{sec:tactic-commands}\<close>
 
 text \<open>
-  The Isar provides separate commands to accommodate tactic-style
-  proof scripts within the same system.  While being outside the
-  orthodox Isar proof language, these might come in handy for
-  interactive exploration and debugging, or even actual tactical proof
-  within new-style theories (to benefit from document preparation, for
-  example).  See also \secref{sec:tactics} for actual tactics, that
-  have been encapsulated as proof methods.  Proper proof methods may
-  be used in scripts, too.
-
   \begin{matharray}{rcl}
     @{command_def "supply"}@{text "\<^sup>*"} & : & @{text "proof(prove) \<rightarrow> proof(prove)"} \\
     @{command_def "apply"}@{text "\<^sup>*"} & : & @{text "proof(prove) \<rightarrow> proof(prove)"} \\
@@ -872,6 +863,15 @@
     @{command_def "back"}@{text "\<^sup>*"} & : & @{text "proof \<rightarrow> proof"} \\
   \end{matharray}
 
+  The Isar language provides separate commands to accommodate tactic-style
+  proof scripts within the same system.  While being outside the
+  orthodox Isar proof language, these might come in handy for
+  interactive exploration and debugging, or even actual tactical proof
+  within new-style theories (to benefit from document preparation, for
+  example).  See also \secref{sec:tactics} for actual tactics, that
+  have been encapsulated as proof methods.  Proper proof methods may
+  be used in scripts, too.
+
   @{rail \<open>
     @@{command supply} (@{syntax thmdef}? @{syntax thmrefs} + @'and')
     ;
@@ -979,83 +979,125 @@
 (*<*)end(*>*)
 
 
-section \<open>Generalized elimination \label{sec:obtain}\<close>
+section \<open>Generalized elimination and case splitting \label{sec:obtain}\<close>
 
 text \<open>
   \begin{matharray}{rcl}
+    @{command_def "consider"} & : & @{text "proof(state) | proof(chain) \<rightarrow> proof(prove)"} \\
     @{command_def "obtain"} & : & @{text "proof(state) | proof(chain) \<rightarrow> proof(prove)"} \\
     @{command_def "guess"}@{text "\<^sup>*"} & : & @{text "proof(state) | proof(chain) \<rightarrow> proof(prove)"} \\
   \end{matharray}
 
-  Generalized elimination means that additional elements with certain
-  properties may be introduced in the current context, by virtue of a
-  locally proven ``soundness statement''.  Technically speaking, the
-  @{command "obtain"} language element is like a declaration of
-  @{command "fix"} and @{command "assume"} (see also see
-  \secref{sec:proof-context}), together with a soundness proof of its
-  additional claim.  According to the nature of existential reasoning,
-  assumptions get eliminated from any result exported from the context
-  later, provided that the corresponding parameters do \emph{not}
-  occur in the conclusion.
+  Generalized elimination means that hypothetical parameters and premises
+  may be introduced in the current context, potentially with a split into
+  cases. This works by virtue of a locally proven rule that establishes the
+  soundness of this temporary context extension. As representative examples,
+  one may think of standard rules from Isabelle/HOL like this:
+
+  \medskip
+  \begin{tabular}{ll}
+  @{text "\<exists>x. B x \<Longrightarrow> (\<And>x. B x \<Longrightarrow> thesis) \<Longrightarrow> thesis"} \\
+  @{text "A \<and> B \<Longrightarrow> (A \<Longrightarrow> B \<Longrightarrow> thesis) \<Longrightarrow> thesis"} \\
+  @{text "A \<or> B \<Longrightarrow> (A \<Longrightarrow> thesis) \<Longrightarrow> (B \<Longrightarrow> thesis) \<Longrightarrow> thesis"} \\
+  \end{tabular}
+  \medskip
+
+  In general, these particular rules and connectives need to get involved at
+  all: this concept works directly in Isabelle/Pure via Isar commands
+  defined below. In particular, the logic of elimination and case splitting
+  is delegated to an Isar proof, which often involves automated tools.
 
   @{rail \<open>
-    @@{command obtain} @{syntax par_name}? (@{syntax vars} + @'and')
+    @@{command consider} @{syntax obtain_clauses}
+    ;
+    @@{command obtain} @{syntax par_name}? (@{syntax "fixes"} + @'and')
       @'where' (@{syntax props} + @'and')
     ;
-    @@{command guess} (@{syntax vars} + @'and')
+    @@{command guess} (@{syntax "fixes"} + @'and')
   \<close>}
 
-  The derived Isar command @{command "obtain"} is defined as follows
-  (where @{text "b\<^sub>1, \<dots>, b\<^sub>k"} shall refer to (optional)
-  facts indicated for forward chaining).
+  \begin{description}
+
+  \item @{command consider}~@{text "(a) \<^vec>x \<WHERE> \<^vec>A \<^vec>x
+  | (b) \<^vec>y \<WHERE> \<^vec>B \<^vec>y | \<dots> "} states a rule for case
+  splitting into separate subgoals, such that each case involves new
+  parameters and premises. After the proof is finished, the resulting rule
+  may be used directly with the @{method cases} proof method
+  (\secref{sec:cases-induct}), in order to perform actual case-splitting of
+  the proof text via @{command case} and @{command next} as usual.
+
+  Optional names in round parentheses refer to case names: in the proof of
+  the rule this is a fact name, in the resulting rule it is used as
+  annotation with the @{attribute_ref case_names} attribute.
+
+  \medskip Formally, the command @{command consider} is defined as derived
+  Isar language element as follows:
+
   \begin{matharray}{l}
-    @{text "\<langle>using b\<^sub>1 \<dots> b\<^sub>k\<rangle>"}~~@{command "obtain"}~@{text "x\<^sub>1 \<dots> x\<^sub>m \<WHERE> a: \<phi>\<^sub>1 \<dots> \<phi>\<^sub>n  \<langle>proof\<rangle> \<equiv>"} \\[1ex]
-    \quad @{command "have"}~@{text "\<And>thesis. (\<And>x\<^sub>1 \<dots> x\<^sub>m. \<phi>\<^sub>1 \<Longrightarrow> \<dots> \<phi>\<^sub>n \<Longrightarrow> thesis) \<Longrightarrow> thesis"} \\
-    \quad @{command "proof"}~@{method succeed} \\
-    \qquad @{command "fix"}~@{text thesis} \\
-    \qquad @{command "assume"}~@{text "that [Pure.intro?]: \<And>x\<^sub>1 \<dots> x\<^sub>m. \<phi>\<^sub>1 \<Longrightarrow> \<dots> \<phi>\<^sub>n \<Longrightarrow> thesis"} \\
-    \qquad @{command "then"}~@{command "show"}~@{text thesis} \\
-    \quad\qquad @{command "apply"}~@{text -} \\
-    \quad\qquad @{command "using"}~@{text "b\<^sub>1 \<dots> b\<^sub>k  \<langle>proof\<rangle>"} \\
-    \quad @{command "qed"} \\
-    \quad @{command "fix"}~@{text "x\<^sub>1 \<dots> x\<^sub>m"}~@{command "assume"}@{text "\<^sup>* a: \<phi>\<^sub>1 \<dots> \<phi>\<^sub>n"} \\
+    @{command "consider"}~@{text "(a) \<^vec>x \<WHERE> \<^vec>A \<^vec>x | (b) \<^vec>y \<WHERE> \<^vec>B \<^vec>y | \<dots> \<equiv>"} \\[1ex]
+    \quad @{command "have"}~@{text "[case_names a b \<dots>]: thesis"} \\
+    \qquad @{text "\<IF> a [Pure.intro?]: \<And>\<^vec>x. \<^vec>A \<^vec>x \<Longrightarrow> thesis"} \\
+    \qquad @{text "\<AND> b [Pure.intro?]: \<And>\<^vec>y. \<^vec>B \<^vec>y \<Longrightarrow> thesis"} \\
+    \qquad @{text "\<AND> \<dots>"} \\
+    \qquad @{text "\<FOR> thesis"} \\
+    \qquad @{command "apply"}~@{text "(insert a b \<dots>)"} \\
   \end{matharray}
 
-  Typically, the soundness proof is relatively straight-forward, often
-  just by canonical automated tools such as ``@{command "by"}~@{text
-  simp}'' or ``@{command "by"}~@{text blast}''.  Accordingly, the
-  ``@{text that}'' reduction above is declared as simplification and
-  introduction rule.
+  See also \secref{sec:goals} for @{keyword "obtains"} in toplevel goal
+  statements, as well as @{command print_statement} to print existing rules
+  in a similar format.
 
-  In a sense, @{command "obtain"} represents at the level of Isar
-  proofs what would be meta-logical existential quantifiers and
-  conjunctions.  This concept has a broad range of useful
-  applications, ranging from plain elimination (or introduction) of
-  object-level existential and conjunctions, to elimination over
-  results of symbolic evaluation of recursive definitions, for
-  example.  Also note that @{command "obtain"} without parameters acts
-  much like @{command "have"}, where the result is treated as a
-  genuine assumption.
+  \item @{command obtain}~@{text "\<^vec>x \<WHERE> \<^vec>A \<^vec>x"}
+  states a generalized elimination rule with exactly one case. After the
+  proof is finished, it is activated for the subsequent proof text: the
+  context is augmented via @{command fix}~@{text "\<^vec>x"} @{command
+  assume}~@{text "\<^vec>A \<^vec>x"}, with special provisions to export
+  later results by discharging these assumptions again.
+
+  Note that according to the parameter scopes within the elimination rule,
+  results \emph{must not} refer to hypothetical parameters; otherwise the
+  export will fail! This restriction conforms to the usual manner of
+  existential reasoning in Natural Deduction.
+
+  \medskip Formally, the command @{command obtain} is defined as derived
+  Isar language element as follows, using an instrumented variant of
+  @{command assume}:
 
-  An alternative name to be used instead of ``@{text that}'' above may
-  be given in parentheses.
+  \begin{matharray}{l}
+    @{command "obtain"}~@{text "\<^vec>x \<WHERE> a: \<^vec>A \<^vec>x  \<langle>proof\<rangle> \<equiv>"} \\[1ex]
+    \quad @{command "have"}~@{text "thesis"} \\
+    \qquad @{text "\<IF> that [Pure.intro?]: \<And>\<^vec>x. \<^vec>A \<^vec>x \<Longrightarrow> thesis"} \\
+    \qquad @{text "\<FOR> thesis"} \\
+    \qquad @{command "apply"}~@{text "(insert that)"} \\
+    \qquad @{text "\<langle>proof\<rangle>"} \\
+    \quad @{command "fix"}~@{text "\<^vec>x"}~@{command "assume"}@{text "\<^sup>* a: \<^vec>A \<^vec>x"} \\
+  \end{matharray}
+
+  \item @{command guess} is similar to @{command obtain}, but it derives the
+  obtained context elements from the course of tactical reasoning in the
+  proof. Thus it can considerably obscure the proof: it is classified as
+  \emph{improper}.
 
-  \medskip The improper variant @{command "guess"} is similar to
-  @{command "obtain"}, but derives the obtained statement from the
-  course of reasoning!  The proof starts with a fixed goal @{text
-  thesis}.  The subsequent proof may refine this to anything of the
-  form like @{text "\<And>x\<^sub>1 \<dots> x\<^sub>m. \<phi>\<^sub>1 \<Longrightarrow> \<dots>
-  \<phi>\<^sub>n \<Longrightarrow> thesis"}, but must not introduce new subgoals.  The
-  final goal state is then used as reduction rule for the obtain
-  scheme described above.  Obtained parameters @{text "x\<^sub>1, \<dots>,
-  x\<^sub>m"} are marked as internal by default, which prevents the
-  proof context from being polluted by ad-hoc variables.  The variable
-  names and type constraints given as arguments for @{command "guess"}
-  specify a prefix of obtained parameters explicitly in the text.
+  A proof with @{command guess} starts with a fixed goal @{text thesis}. The
+  subsequent refinement steps may turn this to anything of the form @{text
+  "\<And>\<^vec>x. \<^vec>A \<^vec>x \<Longrightarrow> thesis"}, but without splitting into new
+  subgoals. The final goal state is then used as reduction rule for the
+  obtain pattern described above. Obtained parameters @{text "\<^vec>x"} are
+  marked as internal by default, and thus inaccessible in the proof text.
+  The variable names and type constraints given as arguments for @{command
+  "guess"} specify a prefix of accessible parameters.
 
-  It is important to note that the facts introduced by @{command
-  "obtain"} and @{command "guess"} may not be polymorphic: any
-  type-variables occurring here are fixed in the present context!
+  \end{description}
+
+  In the proof of @{command consider} and @{command obtain} the local
+  premises are always bound to the fact name ``@{text that}'', according to
+  structured Isar statements involving @{keyword_ref "if"}
+  (\secref{sec:goals}).
+
+  Facts that are established by @{command "obtain"} and @{command "guess"}
+  may not be polymorphic: any type-variables occurring here are fixed in the
+  present context. This is a natural consequence of the role of @{command
+  fix} and @{command assume} in these constructs.
 \<close>
 
 
@@ -1372,6 +1414,7 @@
   \medskip
   \begin{tabular}{llll}
     facts           &                 & arguments   & rule \\\hline
+    @{text "\<turnstile> R"}   & @{method cases} &             & implicit rule @{text R} \\
                     & @{method cases} &             & classical case split \\
                     & @{method cases} & @{text t}   & datatype exhaustion (type of @{text t}) \\
     @{text "\<turnstile> A t"} & @{method cases} & @{text "\<dots>"} & inductive predicate/set elimination (of @{text A}) \\
--- a/src/Doc/isar.sty	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Doc/isar.sty	Sat Jun 13 22:44:22 2015 +0200
@@ -13,6 +13,7 @@
 \newcommand{\indexouternonterm}[1]{\indexdef{}{syntax}{#1}}
 \newcommand{\indexisarelem}[1]{\indexdef{}{element}{#1}}
 
+\newcommand{\isasymIF}{\isakeyword{if}}
 \newcommand{\isasymFOR}{\isakeyword{for}}
 \newcommand{\isasymAND}{\isakeyword{and}}
 \newcommand{\isasymIS}{\isakeyword{is}}
--- a/src/HOL/Hahn_Banach/Hahn_Banach_Ext_Lemmas.thy	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/HOL/Hahn_Banach/Hahn_Banach_Ext_Lemmas.thy	Sat Jun 13 22:44:22 2015 +0200
@@ -69,7 +69,8 @@
     fix y assume "y \<in> F"
     then have "a y \<in> ?S" by blast
     with xi have "a y \<le> xi" by (rule lub.upper)
-  } moreover {
+  }
+  moreover {
     fix y assume y: "y \<in> F"
     from xi have "xi \<le> b y"
     proof (rule lub.least)
@@ -78,7 +79,8 @@
       from u y have "a u \<le> b y" by (rule r)
       with au show "au \<le> b y" by (simp only:)
     qed
-  } ultimately show "\<exists>xi. \<forall>y \<in> F. a y \<le> xi \<and> xi \<le> b y" by blast
+  }
+  ultimately show "\<exists>xi. \<forall>y \<in> F. a y \<le> xi \<and> xi \<le> b y" by blast
 qed
 
 text \<open>
--- a/src/HOL/Hahn_Banach/Hahn_Banach_Sup_Lemmas.thy	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/HOL/Hahn_Banach/Hahn_Banach_Sup_Lemmas.thy	Sat Jun 13 22:44:22 2015 +0200
@@ -126,11 +126,11 @@
     @{text x} and @{text y} are contained in the greater
     one. \label{cases1}\<close>
 
-  from cM c'' c' have "graph H'' h'' \<subseteq> graph H' h' \<or> graph H' h' \<subseteq> graph H'' h''"
-    (is "?case1 \<or> ?case2") ..
+  from cM c'' c' consider "graph H'' h'' \<subseteq> graph H' h'" | "graph H' h' \<subseteq> graph H'' h''"
+    by (blast dest: chainsD)
   then show ?thesis
-  proof
-    assume ?case1
+  proof cases
+    case 1
     have "(x, h x) \<in> graph H'' h''" by fact
     also have "\<dots> \<subseteq> graph H' h'" by fact
     finally have xh:"(x, h x) \<in> graph H' h'" .
@@ -139,14 +139,16 @@
     moreover from cM u and c' have "graph H' h' \<subseteq> graph H h" by blast
     ultimately show ?thesis using * by blast
   next
-    assume ?case2
+    case 2
     from x_hx have "x \<in> H''" ..
-    moreover {
+    moreover have "y \<in> H''"
+    proof -
       have "(y, h y) \<in> graph H' h'" by (rule y_hy)
       also have "\<dots> \<subseteq> graph H'' h''" by fact
       finally have "(y, h y) \<in> graph H'' h''" .
-    } then have "y \<in> H''" ..
-    moreover from cM u and c'' have "graph H'' h'' \<subseteq> graph H h" by blast
+      then show ?thesis ..
+    qed
+    moreover from u c'' have "graph H'' h'' \<subseteq> graph H h" by blast
     ultimately show ?thesis using ** by blast
   qed
 qed
@@ -179,10 +181,11 @@
     or vice versa, since both @{text "G\<^sub>1"} and @{text
     "G\<^sub>2"} are members of @{text c}. \label{cases2}\<close>
 
-  from cM G1 G2 have "G1 \<subseteq> G2 \<or> G2 \<subseteq> G1" (is "?case1 \<or> ?case2") ..
+  from cM G1 G2 consider "G1 \<subseteq> G2" | "G2 \<subseteq> G1"
+    by (blast dest: chainsD)
   then show ?thesis
-  proof
-    assume ?case1
+  proof cases
+    case 1
     with xy' G2_rep have "(x, y) \<in> graph H2 h2" by blast
     then have "y = h2 x" ..
     also
@@ -190,7 +193,7 @@
     then have "z = h2 x" ..
     finally show ?thesis .
   next
-    assume ?case2
+    case 2
     with xz' G1_rep have "(x, z) \<in> graph H1 h1" by blast
     then have "z = h1 x" ..
     also
--- a/src/HOL/Isar_Examples/Hoare_Ex.thy	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/HOL/Isar_Examples/Hoare_Ex.thy	Sat Jun 13 22:44:22 2015 +0200
@@ -224,9 +224,9 @@
   proof hoare
     show "?inv 0 1" by simp
     show "?inv (s + i) (i + 1)" if "?inv s i \<and> i \<noteq> n" for s i
-      using prems by simp
+      using that by simp
     show "s = ?sum n" if "?inv s i \<and> \<not> i \<noteq> n" for s i
-      using prems by simp
+      using that by simp
   qed
 qed
 
--- a/src/HOL/Isar_Examples/Nested_Datatype.thy	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/HOL/Isar_Examples/Nested_Datatype.thy	Sat Jun 13 22:44:22 2015 +0200
@@ -39,10 +39,10 @@
   proof (induct t rule: subst_term.induct)
     show "?P (Var a)" for a by simp
     show "?P (App b ts)" if "?Q ts" for b ts
-      using prems by (simp only: subst_simps)
+      using that by (simp only: subst_simps)
     show "?Q []" by simp
     show "?Q (t # ts)" if "?P t" "?Q ts" for t ts
-      using prems by (simp only: subst_simps)
+      using that by (simp only: subst_simps)
   qed
 qed
 
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/Isar_Examples/Structured_Statements.thy	Sat Jun 13 22:44:22 2015 +0200
@@ -0,0 +1,44 @@
+(*  Title:      HOL/Isar_Examples/Structured_Statements.thy
+    Author:     Makarius
+*)
+
+section \<open>Structured statements within Isar proofs\<close>
+
+theory Structured_Statements
+imports Main
+begin
+
+notepad
+begin
+
+  fix A B :: bool
+
+  have iff_comm: "(A \<and> B) \<longleftrightarrow> (B \<and> A)"
+  proof
+    show "B \<and> A" if "A \<and> B"
+    proof
+      show B using that ..
+      show A using that ..
+    qed
+    show "A \<and> B" if "B \<and> A"
+    proof
+      show A using that ..
+      show B using that ..
+    qed
+  qed
+
+  text \<open>Alternative proof, avoiding redundant copy of symmetric argument.\<close>
+  have iff_comm: "(A \<and> B) \<longleftrightarrow> (B \<and> A)"
+  proof
+    show "B \<and> A" if "A \<and> B" for A B
+    proof
+      show B using that ..
+      show A using that ..
+    qed
+    then show "A \<and> B" if "B \<and> A"
+      by this (rule that)
+  qed
+
+end
+
+end
\ No newline at end of file
--- a/src/HOL/Library/Convex.thy	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/HOL/Library/Convex.thy	Sat Jun 13 22:44:22 2015 +0200
@@ -538,7 +538,7 @@
       by auto
     let ?a = "\<lambda>j. a j / (1 - a i)"
     have a_nonneg: "?a j \<ge> 0" if "j \<in> s" for j
-      using i0 insert prems by fastforce
+      using i0 insert that by fastforce
     have "(\<Sum> j \<in> insert i s. a j) = 1"
       using insert by auto
     then have "(\<Sum> j \<in> s. a j) = 1 - a i"
--- a/src/HOL/Library/Fundamental_Theorem_Algebra.thy	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/HOL/Library/Fundamental_Theorem_Algebra.thy	Sat Jun 13 22:44:22 2015 +0200
@@ -159,8 +159,9 @@
   assume IH: "\<forall>m<n. m \<noteq> 0 \<longrightarrow> (\<exists>z. cmod (1 + b * z ^ m) < 1)"
   assume n: "n \<noteq> 0"
   let ?P = "\<lambda>z n. cmod (1 + b * z ^ n) < 1"
-  {
-    assume e: "even n"
+  show "\<exists>z. ?P z n"
+  proof cases
+    assume "even n"
     then have "\<exists>m. n = 2 * m"
       by presburger
     then obtain m where m: "n = 2 * m"
@@ -170,19 +171,17 @@
     with IH[rule_format, of m] obtain z where z: "?P z m"
       by blast
     from z have "?P (csqrt z) n"
-      by (simp add: m power_mult power2_csqrt)
-    then have "\<exists>z. ?P z n" ..
-  }
-  moreover
-  {
-    assume o: "odd n"
-    have th0: "cmod (complex_of_real (cmod b) / b) = 1"
-      using b by (simp add: norm_divide)
-    from o have "\<exists>m. n = Suc (2 * m)"
+      by (simp add: m power_mult)
+    then show ?thesis ..
+  next
+    assume "odd n"
+    then have "\<exists>m. n = Suc (2 * m)"
       by presburger+
     then obtain m where m: "n = Suc (2 * m)"
       by blast
-    from unimodular_reduce_norm[OF th0] o
+    have th0: "cmod (complex_of_real (cmod b) / b) = 1"
+      using b by (simp add: norm_divide)
+    from unimodular_reduce_norm[OF th0] \<open>odd n\<close>
     have "\<exists>v. cmod (complex_of_real (cmod b) / b + v^n) < 1"
       apply (cases "cmod (complex_of_real (cmod b) / b + 1) < 1")
       apply (rule_tac x="1" in exI)
@@ -206,7 +205,7 @@
     then obtain v where v: "cmod (complex_of_real (cmod b) / b + v^n) < 1"
       by blast
     let ?w = "v / complex_of_real (root n (cmod b))"
-    from odd_real_root_pow[OF o, of "cmod b"]
+    from odd_real_root_pow[OF \<open>odd n\<close>, of "cmod b"]
     have th1: "?w ^ n = v^n / complex_of_real (cmod b)"
       by (simp add: power_divide of_real_power[symmetric])
     have th2:"cmod (complex_of_real (cmod b) / b) = 1"
@@ -222,9 +221,8 @@
       done
     from mult_left_less_imp_less[OF th4 th3]
     have "?P ?w n" unfolding th1 .
-    then have "\<exists>z. ?P z n" ..
-  }
-  ultimately show "\<exists>z. ?P z n" by blast
+    then show ?thesis ..
+  qed
 qed
 
 text \<open>Bolzano-Weierstrass type property for closed disc in complex plane.\<close>
@@ -1020,51 +1018,44 @@
   "(\<forall>x. poly p x = (0::complex) \<longrightarrow> poly q x = 0) \<longleftrightarrow>
     p dvd (q ^ (degree p)) \<or> (p = 0 \<and> q = 0)"
 proof -
-  show ?thesis
-  proof (cases "p = 0")
-    case True
+  consider "p = 0" | "p \<noteq> 0" "degree p = 0" | n where "p \<noteq> 0" "degree p = Suc n"
+    by (cases "degree p") auto
+  then show ?thesis
+  proof cases
+    case 1
     then have eq: "(\<forall>x. poly p x = (0::complex) \<longrightarrow> poly q x = 0) \<longleftrightarrow> q = 0"
       by (auto simp add: poly_all_0_iff_0)
     {
       assume "p dvd (q ^ (degree p))"
       then obtain r where r: "q ^ (degree p) = p * r" ..
-      from r True have False by simp
+      from r 1 have False by simp
     }
-    with eq True show ?thesis by blast
+    with eq 1 show ?thesis by blast
   next
-    case False
-    show ?thesis
-    proof (cases "degree p = 0")
-      case True
-      with \<open>p \<noteq> 0\<close> obtain k where k: "p = [:k:]" "k \<noteq> 0"
-        by (cases p) (simp split: if_splits)
-      then have th1: "\<forall>x. poly p x \<noteq> 0"
+    case 2
+    then obtain k where k: "p = [:k:]" "k \<noteq> 0"
+      by (cases p) (simp split: if_splits)
+    then have th1: "\<forall>x. poly p x \<noteq> 0"
+      by simp
+    from k 2(2) have "q ^ (degree p) = p * [:1/k:]"
+      by (simp add: one_poly_def)
+    then have th2: "p dvd (q ^ (degree p))" ..
+    from 2(1) th1 th2 show ?thesis
+      by blast
+  next
+    case 3
+    {
+      assume "p dvd (q ^ (Suc n))"
+      then obtain u where u: "q ^ (Suc n) = p * u" ..
+      fix x
+      assume h: "poly p x = 0" "poly q x \<noteq> 0"
+      then have "poly (q ^ (Suc n)) x \<noteq> 0"
         by simp
-      from k True have "q ^ (degree p) = p * [:1/k:]"
-        by (simp add: one_poly_def)
-      then have th2: "p dvd (q ^ (degree p))" ..
-      from False th1 th2 show ?thesis
-        by blast
-    next
-      case False
-      assume dp: "degree p \<noteq> 0"
-      then obtain n where n: "degree p = Suc n "
-        by (cases "degree p") auto
-      {
-        assume "p dvd (q ^ (Suc n))"
-        then obtain u where u: "q ^ (Suc n) = p * u" ..
-        {
-          fix x
-          assume h: "poly p x = 0" "poly q x \<noteq> 0"
-          then have "poly (q ^ (Suc n)) x \<noteq> 0"
-            by simp
-          then have False using u h(1)
-            by (simp only: poly_mult) simp
-        }
-      }
-      with n nullstellensatz_lemma[of p q "degree p"] dp
-      show ?thesis by auto
-    qed
+      then have False using u h(1)
+        by (simp only: poly_mult) simp
+    }
+    with 3 nullstellensatz_lemma[of p q "degree p"]
+    show ?thesis by auto
   qed
 qed
 
@@ -1191,7 +1182,7 @@
   shows "\<exists>x. poly (pCons a (pCons b p)) x = (0::complex)"
 proof -
   have False if "h \<noteq> 0" "t = 0" and "pCons a (pCons b p) = pCons h t" for h t
-    using l prems by simp
+    using l that by simp
   then have th: "\<not> (\<exists> h t. h \<noteq> 0 \<and> t = 0 \<and> pCons a (pCons b p) = pCons h t)"
     by blast
   from fundamental_theorem_of_algebra_alt[OF th] show ?thesis
--- a/src/HOL/Multivariate_Analysis/Brouwer_Fixpoint.thy	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/HOL/Multivariate_Analysis/Brouwer_Fixpoint.thy	Sat Jun 13 22:44:22 2015 +0200
@@ -190,10 +190,10 @@
     using \<open>finite simplices\<close> unfolding F_eq by auto
 
   show "card {s \<in> simplices. face f s} = 1" if "f \<in> ?F" "bnd f" for f
-    using bnd prems by auto
+    using bnd that by auto
 
   show "card {s \<in> simplices. face f s} = 2" if "f \<in> ?F" "\<not> bnd f" for f
-    using nbnd prems by auto
+    using nbnd that by auto
 
   show "odd (card {f \<in> {f. \<exists>s\<in>simplices. face f s}. rl ` f = {..n} \<and> bnd f})"
     using odd_card by simp
--- a/src/HOL/ROOT	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/HOL/ROOT	Sat Jun 13 22:44:22 2015 +0200
@@ -623,6 +623,7 @@
     Peirce
     Puzzle
     Summation
+    Structured_Statements
   document_files
     "root.bib"
     "root.tex"
--- a/src/HOL/Tools/Sledgehammer/sledgehammer_fact.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/HOL/Tools/Sledgehammer/sledgehammer_fact.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -222,7 +222,7 @@
 fun is_low_level_class_const s =
   s = @{const_name equal_class.equal} orelse String.isSubstring sep_class_sep s
 
-val sep_that = Long_Name.separator ^ Obtain.thatN
+val sep_that = Long_Name.separator ^ Auto_Bind.thatN
 val skolem_thesis = Name.skolem Auto_Bind.thesisN
 
 fun is_that_fact th =
--- a/src/Pure/Isar/auto_bind.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Pure/Isar/auto_bind.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -8,7 +8,7 @@
 sig
   val thesisN: string
   val thisN: string
-  val premsN: string
+  val thatN: string
   val assmsN: string
   val abs_params: term -> term -> term
   val goal: Proof.context -> term list -> (indexname * term option) list
@@ -23,8 +23,8 @@
 
 val thesisN = "thesis";
 val thisN = "this";
+val thatN = "that";
 val assmsN = "assms";
-val premsN = "prems";
 
 fun strip_judgment ctxt = Object_Logic.drop_judgment ctxt o Logic.strip_assums_concl;
 
--- a/src/Pure/Isar/element.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Pure/Isar/element.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -7,9 +7,12 @@
 
 signature ELEMENT =
 sig
+  type ('typ, 'term) obtain = binding * ((binding * 'typ option * mixfix) list * 'term list)
+  type obtains = (string, string) obtain list
+  type obtains_i = (typ, term) obtain list
   datatype ('typ, 'term) stmt =
     Shows of (Attrib.binding * ('term * 'term list) list) list |
-    Obtains of (binding * ((binding * 'typ option) list * 'term list)) list
+    Obtains of ('typ, 'term) obtain list
   type statement = (string, string) stmt
   type statement_i = (typ, term) stmt
   datatype ('typ, 'term, 'fact) ctxt =
@@ -61,9 +64,13 @@
 
 (* statement *)
 
+type ('typ, 'term) obtain = binding * ((binding * 'typ option * mixfix) list * 'term list);
+type obtains = (string, string) obtain list;
+type obtains_i = (typ, term) obtain list;
+
 datatype ('typ, 'term) stmt =
   Shows of (Attrib.binding * ('term * 'term list) list) list |
-  Obtains of (binding * ((binding * 'typ option) list * 'term list)) list;
+  Obtains of ('typ, 'term) obtain list;
 
 type statement = (string, string) stmt;
 type statement_i = (typ, term) stmt;
@@ -125,14 +132,14 @@
     fun prt_show (a, ts) =
       Pretty.block (Pretty.breaks (prt_binding a ":" @ prt_terms (map fst ts)));
 
-    fun prt_var (x, SOME T) = Pretty.block
+    fun prt_var (x, SOME T, _) = Pretty.block
           [Pretty.str (Binding.name_of x ^ " ::"), Pretty.brk 1, prt_typ T]
-      | prt_var (x, NONE) = Pretty.str (Binding.name_of x);
+      | prt_var (x, NONE, _) = Pretty.str (Binding.name_of x);
     val prt_vars = separate (Pretty.keyword2 "and") o map prt_var;
 
-    fun prt_obtain (_, ([], ts)) = Pretty.block (Pretty.breaks (prt_terms ts))
-      | prt_obtain (_, (xs, ts)) = Pretty.block (Pretty.breaks
-          (prt_vars xs @ [Pretty.keyword2 "where"] @ prt_terms ts));
+    fun prt_obtain (_, ([], props)) = Pretty.block (Pretty.breaks (prt_terms props))
+      | prt_obtain (_, (vars, props)) = Pretty.block (Pretty.breaks
+          (prt_vars vars @ [Pretty.keyword2 "where"] @ prt_terms props));
   in
     fn Shows shows => pretty_items "shows" "and" (map prt_show shows)
      | Obtains obtains => pretty_items "obtains" "|" (map prt_obtain obtains)
@@ -209,7 +216,7 @@
 fun obtain prop ctxt =
   let
     val ((ps, prop'), ctxt') = Variable.focus prop ctxt;
-    fun fix (x, T) = (Binding.name (Variable.revert_fixed ctxt' x), SOME T);
+    fun fix (x, T) = (Binding.name (Variable.revert_fixed ctxt' x), SOME T, NoSyn);
     val xs = map (fix o #2) ps;
     val As = Logic.strip_imp_prems prop';
   in ((Binding.empty, (xs, As)), ctxt') end;
--- a/src/Pure/Isar/isar_syn.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Pure/Isar/isar_syn.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -491,7 +491,8 @@
 
 
 val structured_statement =
-  Parse_Spec.statement -- Parse_Spec.if_prems -- Parse.for_fixes >> (fn ((a, b), c) => (c, b, a));
+  Parse_Spec.statement -- Parse_Spec.if_statement -- Parse.for_fixes
+    >> (fn ((shows, assumes), fixes) => (fixes, assumes, shows));
 
 val _ =
   Outer_Syntax.command @{command_keyword have} "state local goal"
@@ -570,8 +571,12 @@
     >> (Toplevel.proof o Proof.def_cmd));
 
 val _ =
+  Outer_Syntax.command @{command_keyword consider} "state cases rule"
+    (Parse_Spec.obtains >> (Toplevel.proof' o Obtain.consider_cmd));
+
+val _ =
   Outer_Syntax.command @{command_keyword obtain} "generalized elimination"
-    (Parse.parname -- Scan.optional (Parse.fixes --| Parse.where_) [] -- Parse_Spec.statement
+    (Parse.parbinding -- Scan.optional (Parse.fixes --| Parse.where_) [] -- Parse_Spec.statement
       >> (fn ((x, y), z) => Toplevel.proof' (Obtain.obtain_cmd x y z)));
 
 val _ =
--- a/src/Pure/Isar/object_logic.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Pure/Isar/object_logic.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -125,7 +125,7 @@
     val aT = TFree (Name.aT, []);
     val T =
       the_default (aT --> propT) (Sign.const_type (Proof_Context.theory_of ctxt) c)
-      |> Term.map_type_tvar (fn ((x, _), S) => TFree (x, S));
+      |> Term.map_type_tvar (fn ((a, _), S) => TFree (a, S));
     val U = Term.domain_type T handle Match => aT;
   in Const (c, T) $ Free (x, U) end;
 
--- a/src/Pure/Isar/obtain.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Pure/Isar/obtain.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -1,47 +1,21 @@
 (*  Title:      Pure/Isar/obtain.ML
     Author:     Markus Wenzel, TU Muenchen
 
-The 'obtain' and 'guess' language elements -- generalized existence at
-the level of proof texts: 'obtain' involves a proof that certain
-fixes/assumes may be introduced into the present context; 'guess' is
-similar, but derives these elements from the course of reasoning!
-
-  <chain_facts>
-  obtain x where "A x" <proof> ==
-
-  have "!!thesis. (!!x. A x ==> thesis) ==> thesis"
-  proof succeed
-    fix thesis
-    assume that [intro?]: "!!x. A x ==> thesis"
-    <chain_facts>
-    show thesis
-      apply (insert that)
-      <proof>
-  qed
-  fix x assm <<obtain_export>> "A x"
-
-
-  <chain_facts>
-  guess x <proof body> <proof end> ==
-
-  {
-    fix thesis
-    <chain_facts> have "PROP ?guess"
-      apply magic      -- {* turns goal into "thesis ==> #thesis" *}
-      <proof body>
-      apply_end magic  -- {* turns final "(!!x. P x ==> thesis) ==> #thesis" into
-        "#((!!x. A x ==> thesis) ==> thesis)" which is a finished goal state *}
-      <proof end>
-  }
-  fix x assm <<obtain_export>> "A x"
+Generalized existence and cases rules within Isar proof text.
 *)
 
 signature OBTAIN =
 sig
-  val thatN: string
-  val obtain: string -> (binding * typ option * mixfix) list ->
+  val obtains_attributes: ('typ, 'term) Element.obtain list -> attribute list
+  val parse_clause: Proof.context -> term ->
+    (binding * typ option * mixfix) list -> string list -> term
+  val read_obtains: Proof.context -> term -> Element.obtains -> (binding * term) list
+  val cert_obtains: Proof.context -> term -> Element.obtains_i -> (binding * term) list
+  val consider: Element.obtains_i -> bool -> Proof.state -> Proof.state
+  val consider_cmd: Element.obtains -> bool -> Proof.state -> Proof.state
+  val obtain: binding -> (binding * typ option * mixfix) list ->
     (Thm.binding * (term * term list) list) list -> bool -> Proof.state -> Proof.state
-  val obtain_cmd: string -> (binding * string option * mixfix) list ->
+  val obtain_cmd: binding -> (binding * string option * mixfix) list ->
     (Attrib.binding * (string * string list) list) list -> bool -> Proof.state -> Proof.state
   val result: (Proof.context -> tactic) -> thm list -> Proof.context ->
     ((string * cterm) list * thm list) * Proof.context
@@ -52,7 +26,9 @@
 structure Obtain: OBTAIN =
 struct
 
-(** obtain_export **)
+(** specification elements **)
+
+(* obtain_export *)
 
 (*
   [x, A x]
@@ -92,33 +68,136 @@
   (eliminate ctxt rule xs As, eliminate_term ctxt xs);
 
 
+(* result declaration *)
 
-(** obtain **)
+fun obtains_attributes (obtains: ('typ, 'term) Element.obtain list) =
+  let
+    val case_names = obtains |> map_index (fn (i, (b, _)) =>
+      if Binding.is_empty b then string_of_int (i + 1) else Name_Space.base_name b);
+  in [Rule_Cases.consumes (~ (length obtains)), Rule_Cases.case_names case_names] end;
+
 
-fun bind_judgment ctxt name =
+(* obtain thesis *)
+
+fun obtain_thesis ctxt =
   let
-    val ([x], ctxt') = Proof_Context.add_fixes [(Binding.name name, NONE, NoSyn)] ctxt;
-    val (t as _ $ Free v) = Object_Logic.fixed_judgment ctxt x;
+    val ([x], ctxt') =
+      Proof_Context.add_fixes [(Binding.name Auto_Bind.thesisN, NONE, NoSyn)] ctxt;
+    val t = Object_Logic.fixed_judgment ctxt x;
+    val v = dest_Free (Object_Logic.drop_judgment ctxt t);
   in ((v, t), ctxt') end;
 
-val thatN = "that";
+
+(* obtain clauses *)
+
+local
+
+fun prepare_clause parse_prop ctxt thesis vars raw_props =
+  let
+    val (xs', ctxt') = ctxt |> Proof_Context.add_fixes vars;
+    val xs = map (Variable.check_name o #1) vars;
+  in
+    Logic.list_implies (map (parse_prop ctxt') raw_props, thesis)
+    |> fold_rev (Logic.all_constraint (Variable.default_type ctxt')) (xs ~~ xs')
+  end;
+
+fun prepare_obtains prep_var parse_prop ctxt thesis raw_obtains =
+  let
+    val all_types =
+      fold_map prep_var (maps (fn (_, (vs, _)) => vs) raw_obtains)
+        (ctxt |> Context_Position.set_visible false)
+      |> #1 |> map_filter (fn (_, opt_T, _) => opt_T);
+    val types_ctxt = fold Variable.declare_typ all_types ctxt;
+
+    val clauses =
+      raw_obtains |> map (fn (_, (raw_vars, raw_props)) =>
+        let
+          val (vars, vars_ctxt) = fold_map prep_var raw_vars types_ctxt;
+          val clause = prepare_clause parse_prop vars_ctxt thesis vars raw_props;
+        in clause end)
+      |> Syntax.check_terms ctxt;
+  in map fst raw_obtains ~~ clauses end;
+
+in
+
+val parse_clause = prepare_clause Syntax.parse_prop;
+
+val read_obtains = prepare_obtains Proof_Context.read_var Syntax.parse_prop;
+val cert_obtains = prepare_obtains Proof_Context.cert_var (K I);
+
+end;
+
+
+
+(** consider: generalized elimination and cases rule **)
+
+(*
+  consider x where (a) "A x" | y (b) where "B x" | ... ==
+
+  have thesis
+    if a [intro?]: "!!x. A x ==> thesis"
+    and b [intro?]: "!!x. B x ==> thesis"
+    and ...
+    for thesis
+    apply (insert that)
+*)
+
+local
+
+fun gen_consider prep_obtains raw_obtains int state =
+  let
+    val _ = Proof.assert_forward_or_chain state;
+    val ctxt = Proof.context_of state;
+
+    val ((_, thesis), thesis_ctxt) = obtain_thesis ctxt;
+    val obtains = prep_obtains thesis_ctxt thesis raw_obtains;
+    val atts = Rule_Cases.cases_open :: obtains_attributes raw_obtains;
+  in
+    state
+    |> Proof.have NONE (K I)
+      [(Binding.name Auto_Bind.thesisN, NONE, NoSyn)]
+      (map (fn (a, A) => ((a, [Context_Rules.intro_query NONE]), [(A, [])])) obtains)
+      [((Binding.empty, atts), [(thesis, [])])] int
+    |> (fn state' => state'
+        |> Proof.refine_insert (Assumption.local_prems_of (Proof.context_of state') ctxt))
+  end;
+
+in
+
+val consider = gen_consider cert_obtains;
+val consider_cmd = gen_consider read_obtains;
+
+end;
+
+
+
+(** obtain: augmented context based on generalized existence rule **)
+
+(*
+  obtain (a) x where "A x" <proof> ==
+
+  have thesis if a [intro?]: "!!x. A x ==> thesis" for thesis
+    apply (insert that)
+    <proof>
+  fix x assm <<obtain_export>> "A x"
+*)
 
 local
 
 fun gen_obtain prep_att prep_var prep_propp
-    name raw_vars raw_asms int state =
+    that_binding raw_vars raw_asms int state =
   let
     val _ = Proof.assert_forward_or_chain state;
     val ctxt = Proof.context_of state;
-    val chain_facts = if can Proof.assert_chain state then Proof.the_facts state else [];
 
-    (*obtain vars*)
-    val ((xs', vars), fix_ctxt) = ctxt
+    (*vars*)
+    val ((_, thesis), thesis_ctxt) = obtain_thesis ctxt;
+    val ((xs', vars), fix_ctxt) = thesis_ctxt
       |> fold_map prep_var raw_vars
       |-> (fn vars => Proof_Context.add_fixes vars ##>> pair vars);
     val xs = map (Variable.check_name o #1) vars;
 
-    (*obtain asms*)
+    (*asms*)
     val (propss, binds) = prep_propp fix_ctxt (map snd raw_asms);
     val props = flat propss;
     val declare_asms =
@@ -128,7 +207,7 @@
       map (fn ((b, raw_atts), _) => (b, map (prep_att fix_ctxt) raw_atts)) raw_asms ~~
       map (map (rpair [])) propss;
 
-    (*obtain params*)
+    (*params*)
     val (params, params_ctxt) =
       declare_asms fix_ctxt |> fold_map Proof_Context.inferred_param xs' |>> map Free;
     val cparams = map (Thm.cterm_of params_ctxt) params;
@@ -136,37 +215,27 @@
 
     val _ = Variable.warn_extra_tfrees fix_ctxt params_ctxt;
 
-    (*obtain statements*)
-    val thesisN = singleton (Name.variant_list xs) Auto_Bind.thesisN;
-    val (thesis_var, thesis) = #1 (bind_judgment params_ctxt thesisN);
-
-    val that_name = if name = "" then thatN else name;
+    (*statements*)
     val that_prop =
       Logic.list_rename_params xs
         (fold_rev Logic.all params (Logic.list_implies (props, thesis)));
-    val obtain_prop =
-      Logic.list_rename_params [Auto_Bind.thesisN]
-        (Logic.all (Free thesis_var) (Logic.mk_implies (that_prop, thesis)));
 
-    fun after_qed _ =
-      Proof.local_qed (NONE, false)
-      #> `Proof.the_fact #-> (fn rule =>
-        Proof.fix vars
-        #> Proof.map_context declare_asms
-        #> Proof.assm (obtain_export params_ctxt rule cparams) asms);
+    fun after_qed (result_ctxt, results) state' =
+      let val [rule] = Proof_Context.export result_ctxt (Proof.context_of state') (flat results) in
+        state'
+        |> Proof.fix vars
+        |> Proof.map_context declare_asms
+        |> Proof.assm (obtain_export params_ctxt rule cparams) asms
+      end;
   in
     state
-    |> Proof.enter_forward
-    |> Proof.have NONE (K I) [] [] [(Thm.empty_binding, [(obtain_prop, [])])] int
+    |> Proof.have NONE after_qed
+      [(Binding.name Auto_Bind.thesisN, NONE, NoSyn)]
+      [((that_binding, [Context_Rules.intro_query NONE]), [(that_prop, [])])]
+      [(Thm.empty_binding, [(thesis, [])])] int
+    |> (fn state' => state'
+        |> Proof.refine_insert (Assumption.local_prems_of (Proof.context_of state') ctxt))
     |> Proof.map_context (fold Variable.bind_term binds')
-    |> Proof.proof (SOME Method.succeed_text) |> Seq.hd
-    |> Proof.fix [(Binding.name thesisN, NONE, NoSyn)]
-    |> Proof.assume
-      [((Binding.name that_name, [Context_Rules.intro_query NONE]), [(that_prop, [])])]
-    |> `Proof.the_facts
-    ||> Proof.chain_facts chain_facts
-    ||> Proof.show NONE after_qed [] [] [(Thm.empty_binding, [(thesis, [])])] false
-    |-> Proof.refine_insert
   end;
 
 in
@@ -191,7 +260,7 @@
 
 fun result tac facts ctxt =
   let
-    val ((thesis_var, thesis), thesis_ctxt) = bind_judgment ctxt Auto_Bind.thesisN;
+    val ((thesis_var, thesis), thesis_ctxt) = obtain_thesis ctxt;
     val st = Goal.init (Thm.cterm_of ctxt thesis);
     val rule =
       (case SINGLE (Method.insert_tac facts 1 THEN tac thesis_ctxt) st of
@@ -211,7 +280,23 @@
 
 
 
-(** guess **)
+(** guess: obtain based on tactical result **)
+
+(*
+  <chain_facts>
+  guess x <proof body> <proof end> ==
+
+  {
+    fix thesis
+    <chain_facts> have "PROP ?guess"
+      apply magic      -- {* turns goal into "thesis ==> #thesis" *}
+      <proof body>
+      apply_end magic  -- {* turns final "(!!x. P x ==> thesis) ==> #thesis" into
+        "#((!!x. A x ==> thesis) ==> thesis)" which is a finished goal state *}
+      <proof end>
+  }
+  fix x assm <<obtain_export>> "A x"
+*)
 
 local
 
@@ -274,7 +359,7 @@
     val ctxt = Proof.context_of state;
     val chain_facts = if can Proof.assert_chain state then Proof.the_facts state else [];
 
-    val (thesis_var, thesis) = #1 (bind_judgment ctxt Auto_Bind.thesisN);
+    val (thesis_var, thesis) = #1 (obtain_thesis ctxt);
     val vars = ctxt
       |> fold_map prep_var raw_vars |-> fold_map inferred_type
       |> fst |> polymorphic ctxt;
--- a/src/Pure/Isar/parse.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Pure/Isar/parse.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -90,7 +90,7 @@
   val where_: string parser
   val const_decl: (string * string * mixfix) parser
   val const_binding: (binding * string * mixfix) parser
-  val params: (binding * string option) list parser
+  val params: (binding * string option * mixfix) list parser
   val fixes: (binding * string option * mixfix) list parser
   val for_fixes: (binding * string option * mixfix) list parser
   val ML_source: Input.source parser
@@ -358,13 +358,12 @@
 val const_decl = name -- ($$$ "::" |-- !!! typ) -- opt_mixfix >> triple1;
 val const_binding = binding -- ($$$ "::" |-- !!! typ) -- opt_mixfix >> triple1;
 
-val params = Scan.repeat1 binding -- Scan.option ($$$ "::" |-- !!! typ)
-  >> (fn (xs, T) => map (rpair T) xs);
+val param_mixfix = binding -- Scan.option ($$$ "::" |-- typ) -- mixfix' >> (single o triple1);
+val params =
+  Scan.repeat1 binding -- Scan.option ($$$ "::" |-- !!! typ)
+    >> (fn (xs, T) => map (fn x => (x, T, NoSyn)) xs);
 
-val fixes =
-  and_list1 (binding -- Scan.option ($$$ "::" |-- typ) -- mixfix' >> (single o triple1) ||
-    params >> map (fn (x, y) => (x, y, NoSyn))) >> flat;
-
+val fixes = and_list1 (param_mixfix || params) >> flat;
 val for_fixes = Scan.optional ($$$ "for" |-- !!! fixes) [];
 
 
--- a/src/Pure/Isar/parse_spec.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Pure/Isar/parse_spec.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -24,7 +24,8 @@
   val locale_expression: bool -> Expression.expression parser
   val context_element: Element.context parser
   val statement: (Attrib.binding * (string * string list) list) list parser
-  val if_prems: (Attrib.binding * (string * string list) list) list parser
+  val if_statement: (Attrib.binding * (string * string list) list) list parser
+  val obtains: Element.obtains parser
   val general_statement: (Element.context list * Element.statement) parser
   val statement_keyword: string parser
 end;
@@ -72,7 +73,7 @@
 val locale_fixes =
   Parse.and_list1 (Parse.binding -- Scan.option (Parse.$$$ "::" |-- Parse.typ) -- Parse.mixfix
     >> (single o Parse.triple1) ||
-  Parse.params >> map (fn (x, y) => (x, y, NoSyn))) >> flat;
+  Parse.params) >> flat;
 
 val locale_insts =
   Scan.optional
@@ -131,18 +132,19 @@
 (* statements *)
 
 val statement = Parse.and_list1 (opt_thm_name ":" -- Scan.repeat1 Parse.propp);
-
-val if_prems = Scan.optional (Parse.$$$ "if" |-- Parse.!!! statement) [];
+val if_statement = Scan.optional (Parse.$$$ "if" |-- Parse.!!! statement) [];
 
 val obtain_case =
   Parse.parbinding --
-    (Scan.optional (Parse.and_list1 Parse.params --| Parse.where_ >> flat) [] --
+    (Scan.optional (Parse.and_list1 Parse.fixes --| Parse.where_ >> flat) [] --
       (Parse.and_list1 (Scan.repeat1 Parse.prop) >> flat));
 
+val obtains = Parse.enum1 "|" obtain_case;
+
 val general_statement =
   statement >> (fn x => ([], Element.Shows x)) ||
   Scan.repeat context_element --
-   (Parse.$$$ "obtains" |-- Parse.!!! (Parse.enum1 "|" obtain_case) >> Element.Obtains ||
+   (Parse.$$$ "obtains" |-- Parse.!!! obtains >> Element.Obtains ||
     Parse.$$$ "shows" |-- Parse.!!! statement >> Element.Shows);
 
 val statement_keyword = Parse.$$$ "obtains" || Parse.$$$ "shows";
--- a/src/Pure/Isar/proof.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Pure/Isar/proof.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -373,7 +373,7 @@
     val {context = ctxt, facts, mode, goal = _} = top state;
     val verbose = Config.get ctxt Proof_Context.verbose;
 
-    fun prt_goal (SOME (_, (_, {using, goal, ...}))) =
+    fun prt_goal (SOME (_, (_, {statement = _, using, goal, before_qed = _, after_qed = _}))) =
           pretty_sep
             (pretty_facts ctxt "using"
               (if mode <> Backward orelse null using then NONE else SOME using))
@@ -1012,7 +1012,7 @@
           |> (fn (premss, ctxt') => ctxt'
                 |> not (null assumes_propss) ?
                   (snd o Proof_Context.note_thmss ""
-                    [((Binding.name Auto_Bind.premsN, []),
+                    [((Binding.name Auto_Bind.thatN, []),
                       [(Assumption.local_prems_of ctxt' ctxt, [])])])
                 |> (snd o Proof_Context.note_thmss ""
                     (assumes_bindings ~~ map (map (fn th => ([th], []))) premss)));
--- a/src/Pure/Isar/rule_cases.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Pure/Isar/rule_cases.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -47,11 +47,13 @@
   val case_conclusion: string * string list -> attribute
   val is_inner_rule: thm -> bool
   val inner_rule: attribute
+  val is_cases_open: thm -> bool
+  val cases_open: attribute
+  val internalize_params: thm -> thm
   val save: thm -> thm -> thm
   val get: thm -> ((string * string list) * string list) list * int
   val rename_params: string list list -> thm -> thm
   val params: string list list -> attribute
-  val internalize_params: thm -> thm
   val mutual_rule: Proof.context -> thm list -> (int list * thm) option
   val strict_mutual_rule: Proof.context -> thm list -> int list * thm
 end;
@@ -201,7 +203,9 @@
 
 
 
-(** consume facts **)
+(** annotations and operations on rules **)
+
+(* consume facts *)
 
 local
 
@@ -256,8 +260,7 @@
 fun consumes n = Thm.mixed_attribute (apsnd (put_consumes (SOME n)));
 
 
-
-(** equality constraints **)
+(* equality constraints *)
 
 val constraints_tagN = "constraints";
 
@@ -281,8 +284,7 @@
 fun constraints n = Thm.mixed_attribute (apsnd (put_constraints (SOME n)));
 
 
-
-(** case names **)
+(* case names *)
 
 val implode_args = space_implode ";";
 val explode_args = space_explode ";";
@@ -303,8 +305,7 @@
 fun case_names cs = Thm.mixed_attribute (apsnd (name cs));
 
 
-
-(** hyp names **)
+(* hyp names *)
 
 val implode_hyps = implode_args o map (suffix "," o space_implode ",");
 val explode_hyps = map (space_explode "," o unsuffix ",") o explode_args;
@@ -325,8 +326,7 @@
   Thm.mixed_attribute (apsnd (name cs #> add_cases_hyp_names (SOME hs)));
 
 
-
-(** case conclusions **)
+(* case conclusions *)
 
 val case_concl_tagN = "case_conclusion";
 
@@ -355,8 +355,7 @@
 fun case_conclusion concl = Thm.mixed_attribute (apsnd (add_case_concl concl));
 
 
-
-(** inner rule **)
+(* inner rule *)
 
 val inner_rule_tagN = "inner_rule";
 
@@ -372,6 +371,35 @@
 val inner_rule = Thm.mixed_attribute (apsnd (put_inner_rule true));
 
 
+(* parameter names *)
+
+val cases_open_tagN = "cases_open";
+
+fun is_cases_open th =
+  AList.defined (op =) (Thm.get_tags th) cases_open_tagN;
+
+fun put_cases_open cases_open =
+  Thm.untag_rule cases_open_tagN
+  #> cases_open ? Thm.tag_rule (cases_open_tagN, "");
+
+val save_cases_open = put_cases_open o is_cases_open;
+
+val cases_open = Thm.mixed_attribute (apsnd (put_cases_open true));
+
+fun internalize_params rule =
+  if is_cases_open rule then rule
+  else
+    let
+      fun rename prem =
+        let val xs =
+          map (Name.internal o Name.clean o fst) (Logic.strip_params prem)
+        in Logic.list_rename_params xs prem end;
+      fun rename_prems prop =
+        let val (As, C) = Logic.strip_horn prop
+        in Logic.list_implies (map rename As, C) end;
+    in Thm.renamed_prop (rename_prems (Thm.prop_of rule)) rule end;
+
+
 
 (** case declarations **)
 
@@ -383,7 +411,8 @@
   save_case_names th #>
   save_cases_hyp_names th #>
   save_case_concls th #>
-  save_inner_rule th;
+  save_inner_rule th #>
+  save_cases_open th;
 
 fun get th =
   let
@@ -410,20 +439,6 @@
 fun params xss = Thm.rule_attribute (K (rename_params xss));
 
 
-(* internalize parameter names *)
-
-fun internalize_params rule =
-  let
-    fun rename prem =
-      let val xs =
-        map (Name.internal o Name.clean o fst) (Logic.strip_params prem)
-      in Logic.list_rename_params xs prem end;
-    fun rename_prems prop =
-      let val (As, C) = Logic.strip_horn prop
-      in Logic.list_implies (map rename As, C) end;
-  in Thm.renamed_prop (rename_prems (Thm.prop_of rule)) rule end;
-
-
 
 (** mutual_rule **)
 
--- a/src/Pure/Isar/specification.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Pure/Isar/specification.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -103,32 +103,14 @@
 
 local
 
-fun close_forms ctxt i xs As =
+fun close_forms ctxt i As =
   let
-    val commons = map #1 xs;
-    val _ =
-      (case duplicates (op =) commons of [] => ()
-      | dups => error ("Duplicate local variables " ^ commas_quote dups));
-    val frees = rev (fold (Variable.add_free_names ctxt) As (rev commons));
+    val xs = rev (fold (Variable.add_free_names ctxt) As []);
     val types =
-      map (Type_Infer.param i o rpair []) (Name.invent Name.context Name.aT (length frees));
-    val uniform_typing = the o AList.lookup (op =) (frees ~~ types);
-
-    fun abs_body lev y (Abs (x, T, b)) = Abs (x, T, abs_body (lev + 1) y b)
-      | abs_body lev y (t $ u) = abs_body lev y t $ abs_body lev y u
-      | abs_body lev y (t as Free (x, T)) =
-          if x = y then Type.constraint (uniform_typing x) (Type.constraint T (Bound lev))
-          else t
-      | abs_body _ _ a = a;
-    fun close (y, U) B =
-      let val B' = abs_body 0 y (Term.incr_boundvars 1 B)
-      in if Term.is_dependent B' then Logic.all_const dummyT $ Abs (y, U, B') else B end;
-    fun close_form A =
-      let
-        val occ_frees = rev (Variable.add_free_names ctxt A []);
-        val bounds = xs @ map (rpair dummyT) (subtract (op =) commons occ_frees);
-      in fold_rev close bounds A end;
-  in map close_form As end;
+      map (Type_Infer.param i o rpair []) (Name.invent Name.context Name.aT (length xs));
+    val uniform_typing = AList.lookup (op =) (xs ~~ types);
+    val close = fold_rev (Logic.dependent_all_constraint uniform_typing) (xs ~~ xs);
+  in map close As end;
 
 fun prepare prep_var parse_prop prep_att do_close raw_vars raw_specss ctxt =
   let
@@ -145,7 +127,7 @@
     val specs =
       (if do_close then
         #1 (fold_map
-            (fn Ass => fn i => (burrow (close_forms params_ctxt i []) Ass, i + 1)) Asss' idx)
+            (fn Ass => fn i => (burrow (close_forms params_ctxt i) Ass, i + 1)) Asss' idx)
       else Asss')
       |> flat |> burrow (Syntax.check_props params_ctxt);
     val specs_ctxt = params_ctxt |> (fold o fold) Variable.declare_term specs;
@@ -347,11 +329,9 @@
       in (([], prems, stmt, NONE), goal_ctxt) end
   | Element.Obtains obtains =>
       let
-        val case_names = obtains |> map_index (fn (i, (b, _)) =>
-          if Binding.is_empty b then string_of_int (i + 1) else Name_Space.base_name b);
         val constraints = obtains |> map (fn (_, (vars, _)) =>
           Element.Constrains
-            (vars |> map_filter (fn (x, SOME T) => SOME (Variable.check_name x, T) | _ => NONE)));
+            (vars |> map_filter (fn (x, SOME T, _) => SOME (Variable.check_name x, T) | _ => NONE)));
 
         val raw_propp = obtains |> map (fn (_, (_, props)) => map (rpair []) props);
         val (propp, elems_ctxt) = prep_stmt (elems @ constraints) raw_propp ctxt;
@@ -360,7 +340,7 @@
 
         fun assume_case ((name, (vars, _)), asms) ctxt' =
           let
-            val bs = map fst vars;
+            val bs = map (fn (b, _, _) => b) vars;
             val xs = map Variable.check_name bs;
             val props = map fst asms;
             val (params, _) = ctxt'
@@ -377,8 +357,7 @@
             |>> (fn [(_, [th])] => th)
           end;
 
-        val more_atts = map (Attrib.internal o K)
-          [Rule_Cases.consumes (~ (length obtains)), Rule_Cases.case_names case_names];
+        val more_atts = map (Attrib.internal o K) (Obtain.obtains_attributes obtains);
         val prems = Assumption.local_prems_of elems_ctxt ctxt;
         val stmt = [((Binding.empty, []), [(thesis, [])])];
 
@@ -386,7 +365,7 @@
           |> (snd o Proof_Context.add_fixes [(Binding.name Auto_Bind.thesisN, NONE, NoSyn)])
           |> fold_map assume_case (obtains ~~ propp)
           |-> (fn ths =>
-            Proof_Context.note_thmss "" [((Binding.name Obtain.thatN, []), [(ths, [])])] #>
+            Proof_Context.note_thmss "" [((Binding.name Auto_Bind.thatN, []), [(ths, [])])] #>
             #2 #> pair ths);
       in ((more_atts, prems, stmt, SOME facts), goal_ctxt) end);
 
--- a/src/Pure/Pure.thy	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Pure/Pure.thy	Sat Jun 13 22:44:22 2015 +0200
@@ -55,6 +55,7 @@
   and "supply" :: prf_script % "proof"
   and "using" "unfolding" :: prf_decl % "proof"
   and "fix" "assume" "presume" "def" :: prf_asm % "proof"
+  and "consider" :: prf_goal % "proof"
   and "obtain" :: prf_asm_goal % "proof"
   and "guess" :: prf_asm_goal_script % "proof"
   and "let" "write" :: prf_decl % "proof"
--- a/src/Pure/logic.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Pure/logic.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -12,6 +12,8 @@
   val is_all: term -> bool
   val dest_all: term -> (string * typ) * term
   val list_all: (string * typ) list * term -> term
+  val all_constraint: (string -> typ option) -> string * string -> term -> term
+  val dependent_all_constraint: (string -> typ option) -> string * string -> term -> term
   val mk_equals: term * term -> term
   val dest_equals: term -> term * term
   val implies: term
@@ -109,6 +111,35 @@
   | list_all ((a, T) :: vars, t) = all_const T $ Abs (a, T, list_all (vars, t));
 
 
+(* operations before type-inference *)
+
+local
+
+fun abs_body default_type z tm =
+  let
+    fun abs lev (Abs (x, T, b)) = Abs (x, T, abs (lev + 1) b)
+      | abs lev (t $ u) = abs lev t $ abs lev u
+      | abs lev (a as Free (x, T)) =
+          if x = z then
+            Type.constraint (the_default dummyT (default_type x))
+              (Type.constraint T (Bound lev))
+          else a
+      | abs _ a = a;
+  in abs 0 (Term.incr_boundvars 1 tm) end;
+
+in
+
+fun all_constraint default_type (y, z) t =
+  all_const dummyT $ Abs (y, dummyT, abs_body default_type z t);
+
+fun dependent_all_constraint default_type (y, z) t =
+  let val t' = abs_body default_type z t
+  in if Term.is_dependent t' then all_const dummyT $ Abs (y, dummyT, t') else t end;
+
+end;
+
+
+
 (** equality **)
 
 fun mk_equals (t, u) =
--- a/src/Tools/induct.ML	Sat Jun 13 19:23:41 2015 +0100
+++ b/src/Tools/induct.ML	Sat Jun 13 22:44:22 2015 +0200
@@ -483,25 +483,32 @@
       |> simp ? mark_constraints (Rule_Cases.get_constraints r) ctxt
       |> pair (Rule_Cases.get r);
 
+    val (opt_rule', facts') =
+      (case (opt_rule, facts) of
+        (NONE, th :: ths) =>
+          if is_some (Object_Logic.elim_concl ctxt th) then (SOME th, ths)
+          else (opt_rule, facts)
+      | _ => (opt_rule, facts));
+
     val ruleq =
-      (case opt_rule of
+      (case opt_rule' of
         SOME r => Seq.single (inst_rule r)
       | NONE =>
-          (get_casesP ctxt facts @ get_casesT ctxt insts @ [Induct_Args.cases_default])
+          (get_casesP ctxt facts' @ get_casesT ctxt insts @ [Induct_Args.cases_default])
           |> tap (trace_rules ctxt casesN)
           |> Seq.of_list |> Seq.maps (Seq.try inst_rule));
   in
     fn i => fn st =>
       ruleq
-      |> Seq.maps (Rule_Cases.consume ctxt [] facts)
-      |> Seq.maps (fn ((cases, (_, more_facts)), rule) =>
+      |> Seq.maps (Rule_Cases.consume ctxt [] facts')
+      |> Seq.maps (fn ((cases, (_, facts'')), rule) =>
         let
           val rule' = rule
             |> simp ? (simplified_rule' ctxt #> unmark_constraints ctxt);
         in
           CASES (Rule_Cases.make_common ctxt
               (Thm.prop_of (Rule_Cases.internalize_params rule')) cases)
-            ((Method.insert_tac more_facts THEN' resolve_tac ctxt [rule'] THEN_ALL_NEW
+            ((Method.insert_tac facts'' THEN' resolve_tac ctxt [rule'] THEN_ALL_NEW
                 (if simp then TRY o trivial_tac ctxt else K all_tac)) i) st
         end)
   end;