author  haftmann 
Fri, 20 Apr 2007 11:21:35 +0200  
changeset 22737  d87ccbcc2702 
parent 21404  eb85850d3eb7 
child 25707  0a599404f5a1 
permissions  rwrr 
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(* Title: HOL/ex/Records.thy 
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ID: $Id$ 

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Author: Wolfgang Naraschewski, Norbert Schirmer and Markus Wenzel, 
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TU Muenchen 
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*) 
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header {* Using extensible records in HOL  points and coloured points *} 

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theory Records imports Main begin 
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subsection {* Points *} 

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record point = 

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xpos :: nat 
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ypos :: nat 

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text {* 

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Apart many other things, above record declaration produces the 
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following theorems: 

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*} 
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thm "point.simps" 
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thm "point.iffs" 

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thm "point.defs" 
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text {* 

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The set of theorems @{thm [source] point.simps} is added 
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automatically to the standard simpset, @{thm [source] point.iffs} is 

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added to the Classical Reasoner and Simplifier context. 

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\medskip Record declarations define new types and type abbreviations: 
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@{text [display] 
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" point = \<lparr>xpos :: nat, ypos :: nat\<rparr> = () point_ext_type 
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'a point_scheme = \<lparr>xpos :: nat, ypos :: nat, ... :: 'a\<rparr> = 'a point_ext_type"} 
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*} 
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consts foo2 :: "( xpos :: nat, ypos :: nat )" 
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consts foo4 :: "'a => ( xpos :: nat, ypos :: nat, ... :: 'a )" 

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subsubsection {* Introducing concrete records and record schemes *} 

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definition 
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foo1 :: point 

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where 

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foo1_def: "foo1 = ( xpos = 1, ypos = 0 )" 

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definition 

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foo3 :: "'a => 'a point_scheme" 

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where 

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foo3_def: "foo3 ext = ( xpos = 1, ypos = 0, ... = ext )" 

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subsubsection {* Record selection and record update *} 

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definition 
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getX :: "'a point_scheme => nat" where 
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"getX r = xpos r" 
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definition 
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setX :: "'a point_scheme => nat => 'a point_scheme" where 
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"setX r n = r ( xpos := n )" 
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subsubsection {* Some lemmas about records *} 

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text {* Basic simplifications. *} 
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lemma "point.make n p = ( xpos = n, ypos = p )" 
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by (simp only: point.make_def) 

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lemma "xpos ( xpos = m, ypos = n, ... = p ) = m" 
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by simp 
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lemma "( xpos = m, ypos = n, ... = p ) ( xpos:= 0 ) = ( xpos = 0, ypos = n, ... = p )" 
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by simp 
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text {* \medskip Equality of records. *} 
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lemma "n = n' ==> p = p' ==> ( xpos = n, ypos = p ) = ( xpos = n', ypos = p' )" 
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 "introduction of concrete record equality" 
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by simp 

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lemma "( xpos = n, ypos = p ) = ( xpos = n', ypos = p' ) ==> n = n'" 
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 "elimination of concrete record equality" 
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by simp 

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lemma "r ( xpos := n ) ( ypos := m ) = r ( ypos := m ) ( xpos := n )" 
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 "introduction of abstract record equality" 
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by simp 

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lemma "r ( xpos := n ) = r ( xpos := n' ) ==> n = n'" 
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 "elimination of abstract record equality (manual proof)" 
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proof  

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assume "r ( xpos := n ) = r ( xpos := n' )" (is "?lhs = ?rhs") 
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hence "xpos ?lhs = xpos ?rhs" by simp 

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thus ?thesis by simp 
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qed 

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text {* \medskip Surjective pairing *} 
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lemma "r = ( xpos = xpos r, ypos = ypos r )" 
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by simp 
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lemma "r = ( xpos = xpos r, ypos = ypos r, ... = point.more r )" 
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by simp 
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text {* 
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\medskip Representation of records by cases or (degenerate) 
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induction. 

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*} 
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lemma "r( xpos := n ) ( ypos := m ) = r ( ypos := m ) ( xpos := n )" 
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proof (cases r) 
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fix xpos ypos more 

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assume "r = ( xpos = xpos, ypos = ypos, ... = more )" 

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thus ?thesis by simp 

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qed 

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lemma "r ( xpos := n ) ( ypos := m ) = r ( ypos := m ) ( xpos := n )" 

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proof (induct r) 

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fix xpos ypos more 

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show "( xpos = xpos, ypos = ypos, ... = more ) ( xpos := n, ypos := m ) = 

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( xpos = xpos, ypos = ypos, ... = more ) ( ypos := m, xpos := n )" 

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by simp 
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qed 

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lemma "r ( xpos := n ) ( xpos := m ) = r ( xpos := m )" 
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proof (cases r) 

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fix xpos ypos more 

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assume "r = \<lparr>xpos = xpos, ypos = ypos, \<dots> = more\<rparr>" 

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thus ?thesis by simp 

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qed 
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lemma "r ( xpos := n ) ( xpos := m ) = r ( xpos := m )" 
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proof (cases r) 

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case fields 

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thus ?thesis by simp 

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qed 

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lemma "r ( xpos := n ) ( xpos := m ) = r ( xpos := m )" 

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by (cases r) simp 

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text {* 
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\medskip Concrete records are type instances of record schemes. 

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*} 

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definition 
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foo5 :: nat where 
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"foo5 = getX ( xpos = 1, ypos = 0 )" 
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text {* \medskip Manipulating the ``@{text "..."}'' (more) part. *} 
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definition 
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incX :: "'a point_scheme => 'a point_scheme" where 
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"incX r = ( xpos = xpos r + 1, ypos = ypos r, ... = point.more r )" 
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lemma "incX r = setX r (Suc (getX r))" 
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by (simp add: getX_def setX_def incX_def) 

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text {* An alternative definition. *} 
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definition 
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incX' :: "'a point_scheme => 'a point_scheme" where 
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"incX' r = r ( xpos := xpos r + 1 )" 
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subsection {* Coloured points: record extension *} 

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datatype colour = Red  Green  Blue 

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record cpoint = point + 

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colour :: colour 

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text {* 

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The record declaration defines a new type constructure and abbreviations: 
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@{text [display] 
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" cpoint = ( xpos :: nat, ypos :: nat, colour :: colour ) = 
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() cpoint_ext_type point_ext_type 
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'a cpoint_scheme = ( xpos :: nat, ypos :: nat, colour :: colour, ... :: 'a ) = 
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'a cpoint_ext_type point_ext_type"} 
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*} 
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consts foo6 :: cpoint 

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consts foo7 :: "( xpos :: nat, ypos :: nat, colour :: colour )" 
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consts foo8 :: "'a cpoint_scheme" 

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consts foo9 :: "( xpos :: nat, ypos :: nat, colour :: colour, ... :: 'a )" 

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text {* 
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Functions on @{text point} schemes work for @{text cpoints} as well. 

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*} 

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foo10 :: nat where 
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"foo10 = getX ( xpos = 2, ypos = 0, colour = Blue )" 
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subsubsection {* Noncoercive structural subtyping *} 

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text {* 
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Term @{term foo11} has type @{typ cpoint}, not type @{typ point}  

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Great! 

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*} 

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foo11 :: cpoint where 
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"foo11 = setX ( xpos = 2, ypos = 0, colour = Blue ) 0" 
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subsection {* Other features *} 

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text {* Field names contribute to record identity. *} 
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record point' = 

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xpos' :: nat 
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ypos' :: nat 

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text {* 
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\noindent May not apply @{term getX} to @{term [source] "( xpos' = 
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2, ypos' = 0 )"}  type error. 

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*} 
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text {* \medskip Polymorphic records. *} 
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record 'a point'' = point + 

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content :: 'a 

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types cpoint'' = "colour point''" 

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end 