summary |
shortlog |
changelog |
graph |
tags |
bookmarks |
branches |
files |
changeset |
raw | gz |
help

author | paulson |

Wed, 11 Jul 2001 17:55:46 +0200 | |

changeset 11410 | b3b61ea9632c |

parent 11409 | f0bcb3dfa7d6 |

child 11411 | c315dda16748 |

indexing

--- a/doc-src/TutorialI/Sets/sets.tex Wed Jul 11 15:21:07 2001 +0200 +++ b/doc-src/TutorialI/Sets/sets.tex Wed Jul 11 17:55:46 2001 +0200 @@ -31,15 +31,15 @@ HOL's set theory should not be confused with traditional, untyped set theory, in which everything is a set. Our sets are typed. In a given set, all elements have the same type, say~$\tau$, and the set itself has type -\isa{$\tau$~set}. +$\tau$~\tydx{set}. -We begin with \bfindex{intersection}, \bfindex{union} and -\bfindex{complement}. In addition to the -\bfindex{membership relation}, there is a symbol for its negation. These +We begin with \textbf{intersection}, \textbf{union} and +\textbf{complement}. In addition to the +\textbf{membership relation}, there is a symbol for its negation. These points can be seen below. -Here are the natural deduction rules for intersection. Note the -resemblance to those for conjunction. +Here are the natural deduction rules for \rmindex{intersection}. Note +the resemblance to those for conjunction. \begin{isabelle} \isasymlbrakk c\ \isasymin\ A;\ c\ \isasymin\ B\isasymrbrakk\ \isasymLongrightarrow\ c\ \isasymin\ A\ \isasyminter\ B% @@ -50,7 +50,8 @@ \rulename{IntD2} \end{isabelle} -Here are two of the many installed theorems concerning set complement. +Here are two of the many installed theorems concerning set +complement.\index{complement!of a set}% Note that it is denoted by a minus sign. \begin{isabelle} (c\ \isasymin\ -\ A)\ =\ (c\ \isasymnotin\ A) @@ -126,8 +127,8 @@ {\isasymLongrightarrow}\ A\ =\ B \rulename{set_ext} \end{isabelle} -Extensionality is often expressed as -$A=B\iff A\subseteq B\conj B\subseteq A$. +Extensionality can be expressed as +$A=B\iff (A\subseteq B)\conj (B\subseteq A)$. The following rules express both directions of this equivalence. Proving a set equation using \isa{equalityI} allows the two inclusions to be proved independently. @@ -145,8 +146,8 @@ \subsection{Finite Set Notation} -\indexbold{sets!notation for finite}\index{*insert (constant)} -Finite sets are expressed using the constant \isa{insert}, which is +\indexbold{sets!notation for finite} +Finite sets are expressed using the constant \cdx{insert}, which is a form of union: \begin{isabelle} insert\ a\ A\ =\ \isacharbraceleft a\isacharbraceright\ \isasymunion\ A @@ -232,8 +233,8 @@ \isasymand\ p{\isasymin}prime\ \isasymand\ q{\isasymin}prime\isacharbraceright" \end{isabelle} -The proof is trivial because the left and right hand side -of the expression are synonymous. The syntax appearing on the +The left and right hand sides +of this equation are identical. The syntax used in the left-hand side abbreviates the right-hand side: in this case, all numbers that are the product of two primes. The syntax provides a neat way of expressing any set given by an expression built up from variables @@ -370,7 +371,7 @@ A\cup B$ is replaced by $x\in A\vee x\in B$. The internal form of a comprehension involves the constant -\isa{Collect},\index{*Collect (constant)} +\cdx{Collect}, which occasionally appears when a goal or theorem is displayed. For example, \isa{Collect\ P} is the same term as \isa{\isacharbraceleft x.\ P\ x\isacharbraceright}. The same thing can @@ -383,25 +384,22 @@ \isa{Bex\ A\ P}\index{*Bex (constant)} is \isa{\isasymexists z\isasymin A.\ P\ x}. For indexed unions and intersections, you may see the constants -\isa{UNION}\index{*UNION (constant)} and -\isa{INTER}\index{*INTER (constant)}\@. -The internal constant for $\varepsilon x.P(x)$ is -\isa{Eps}\index{*Eps (constant)}. - +\cdx{UNION} and \cdx{INTER}\@. +The internal constant for $\varepsilon x.P(x)$ is~\cdx{Eps}. We have only scratched the surface of Isabelle/HOL's set theory. -One primitive not mentioned here is the powerset operator -{\isa{Pow}}. Hundreds of theorems are proved in theory \isa{Set} and its +Hundreds of theorems are proved in theory \isa{Set} and its descendants. \subsection{Finiteness and Cardinality} \index{sets!finite}% -The predicate \isa{finite} holds of all finite sets. Isabelle/HOL includes -many familiar theorems about finiteness and cardinality -(\isa{card}). For example, we have theorems concerning the cardinalities -of unions, intersections and the powerset:\index{cardinality} +The predicate \sdx{finite} holds of all finite sets. Isabelle/HOL +includes many familiar theorems about finiteness and cardinality +(\cdx{card}). For example, we have theorems concerning the +cardinalities of unions, intersections and the +powerset:\index{cardinality} % \begin{isabelle} {\isasymlbrakk}finite\ A;\ finite\ B\isasymrbrakk\isanewline @@ -426,9 +424,9 @@ \begin{warn} The term \isa{finite\ A} is defined via a syntax translation as an -abbreviation for \isa{A \isasymin Finites}, where the constant \isa{Finites} -denotes the set of all finite sets of a given type. There is no constant -\isa{finite}. +abbreviation for \isa{A \isasymin Finites}, where the constant +\cdx{Finites} denotes the set of all finite sets of a given type. There +is no constant \isa{finite}. \end{warn} \index{sets|)} @@ -454,7 +452,7 @@ \rulename{ext} \end{isabelle} -\indexbold{function updates}% +\indexbold{updating a function}% Function \textbf{update} is useful for modelling machine states. It has the obvious definition and many useful facts are proved about it. In particular, the following equation is installed as a simplification @@ -560,9 +558,11 @@ \rulename{expand_fun_eq} \end{isabelle} % -This is just a restatement of extensionality. Our lemma states -that an injection can be cancelled from the left -side of function composition: +This is just a restatement of +extensionality.\indexbold{extensionality!for functions} +Our lemma +states that an injection can be cancelled from the left side of +function composition: \begin{isabelle} \isacommand{lemma}\ "inj\ f\ \isasymLongrightarrow\ (f\ o\ g\ =\ f\ o\ h)\ =\ (g\ =\ h)"\isanewline \isacommand{apply}\ (simp\ add:\ expand_fun_eq\ inj_on_def)\isanewline @@ -618,10 +618,11 @@ \end{isabelle} \medskip - A function's \textbf{range} is the set of values that the function can +\index{range!of a function}% +A function's \textbf{range} is the set of values that the function can take on. It is, in fact, the image of the universal set under -that function. There is no constant {\isa{range}}. Instead, {\isa{range}} -abbreviates an application of image to {\isa{UNIV}}: +that function. There is no constant \isa{range}. Instead, +\sdx{range} abbreviates an application of image to \isa{UNIV}: \begin{isabelle} \ \ \ \ \ range\ f\ {\isasymrightleftharpoons}\ f`UNIV @@ -665,7 +666,8 @@ \end{isabelle} \indexbold{composition!of relations}% -\textbf{Composition} of relations (the infix \isa{O}) is also available: +\textbf{Composition} of relations (the infix \sdx{O}) is also +available: \begin{isabelle} r\ O\ s\ \isasymequiv\ \isacharbraceleft(x,z).\ \isasymexists y.\ (x,y)\ \isasymin\ s\ \isasymand\ (y,z)\ \isasymin\ r\isacharbraceright \rulename{comp_def} @@ -715,20 +717,9 @@ \end{isabelle} It satisfies many similar laws. -%Image under relations, like image under functions, distributes over unions: -%\begin{isabelle} -%r\ ``\ -%({\isasymUnion}x\isasyminA.\ -%B\ -%x)\ =\ -%({\isasymUnion}x\isasyminA.\ -%r\ ``\ B\ -%x) -%\rulename{Image_UN} -%\end{isabelle} - - -The \bfindex{domain} and \bfindex{range} of a relation are defined in the +\index{domain!of a relation}% +\index{range!of a relation}% +The \textbf{domain} and \textbf{range} of a relation are defined in the standard way: \begin{isabelle} (a\ \isasymin\ Domain\ r)\ =\ (\isasymexists y.\ (a,y)\ \isasymin\ @@ -743,11 +734,10 @@ \end{isabelle} Iterated composition of a relation is available. The notation overloads -that of exponentiation: +that of exponentiation. Two simplification rules are installed: \begin{isabelle} R\ \isacharcircum\ \isadigit{0}\ =\ Id\isanewline R\ \isacharcircum\ Suc\ n\ =\ R\ O\ R\isacharcircum n -\rulename{relpow.simps} \end{isabelle} \subsection{The Reflexive and Transitive Closure} @@ -810,9 +800,9 @@ \subsection{A Sample Proof} -The reflexive transitive closure also commutes with the converse. -Let us examine the proof. Each direction of the equivalence is -proved separately. The two proofs are almost identical. Here +The reflexive transitive closure also commutes with the converse +operator. Let us examine the proof. Each direction of the equivalence +is proved separately. The two proofs are almost identical. Here is the first one: \begin{isabelle} \isacommand{lemma}\ rtrancl_converseD:\ "(x,y)\ \isasymin \ @@ -856,9 +846,10 @@ \end{isabelle} \begin{warn} -Note that \isa{blast} cannot prove this theorem. Here is a subgoal that -arises internally after the rules \isa{equalityI} and \isa{subsetI} have -been applied: +This trivial proof requires \isa{auto} rather than \isa{blast} because +of a subtle issue involving ordered pairs. Here is a subgoal that +arises internally after the rules +\isa{equalityI} and \isa{subsetI} have been applied: \begin{isabelle} \ 1.\ \isasymAnd x.\ x\ \isasymin \ (r\isasyminverse )\isactrlsup *\ \isasymLongrightarrow \ x\ \isasymin \ (r\isactrlsup *)\isasyminverse @@ -867,7 +858,7 @@ %\isasymLongrightarrow \ x\ \isasymin \ (r\isasyminverse )\isactrlsup * \end{isabelle} \par\noindent -We cannot use \isa{rtrancl_converseD}\@. It refers to +We cannot apply \isa{rtrancl_converseD}\@. It refers to ordered pairs, while \isa{x} is a variable of product type. The \isa{simp} and \isa{blast} methods can do nothing, so let us try \isa{clarify}: @@ -888,7 +879,7 @@ \index{relations!well-founded|(}% A well-founded relation captures the notion of a terminating process. -Each \isacommand{recdef}\index{recdef@\isacommand{recdef}} +Each \commdx{recdef} declaration must specify a well-founded relation that justifies the termination of the desired recursive function. Most of the forms of induction found in mathematics are merely special cases of @@ -914,7 +905,7 @@ well-founded induction only in \S\ref{sec:CTL-revisited}. \end{warn} -Isabelle/HOL declares \isa{less_than} as a relation object, +Isabelle/HOL declares \cdx{less_than} as a relation object, that is, a set of pairs of natural numbers. Two theorems tell us that this relation behaves as expected and that it is well-founded: \begin{isabelle} @@ -950,11 +941,12 @@ \rulename{wf_measure} \end{isabelle} -Of the other constructions, the most important is the \textbf{lexicographic -product} of two relations. It expresses the standard dictionary -ordering over pairs. We write \isa{ra\ <*lex*>\ rb}, where \isa{ra} -and \isa{rb} are the two operands. The lexicographic product satisfies the -usual definition and it preserves well-foundedness: +Of the other constructions, the most important is the +\bfindex{lexicographic product} of two relations. It expresses the +standard dictionary ordering over pairs. We write \isa{ra\ <*lex*>\ +rb}, where \isa{ra} and \isa{rb} are the two operands. The +lexicographic product satisfies the usual definition and it preserves +well-foundedness: \begin{isabelle} ra\ <*lex*>\ rb\ \isasymequiv \isanewline \ \ \isacharbraceleft ((a,b),(a',b')).\ (a,a')\ \isasymin \ ra\ @@ -976,10 +968,11 @@ discuss it. \medskip -Induction comes in many forms, including traditional mathematical -induction, structural induction on lists and induction on size. All are -instances of the following rule, for a suitable well-founded -relation~$\prec$: +Induction\index{induction!well-founded|(} +comes in many forms, +including traditional mathematical induction, structural induction on +lists and induction on size. All are instances of the following rule, +for a suitable well-founded relation~$\prec$: \[ \infer{P(a)}{\infer*{P(x)}{[\forall y.\, y\prec x \imp P(y)]}} \] To show $P(a)$ for a particular term~$a$, it suffices to show $P(x)$ for arbitrary~$x$ under the assumption that $P(y)$ holds for $y\prec x$. @@ -1001,7 +994,8 @@ For example, the predecessor relation on the natural numbers is well-founded; induction over it is mathematical induction. The ``tail of'' relation on lists is well-founded; induction over -it is structural induction. +it is structural induction.% +\index{induction!well-founded|)}% \index{relations!well-founded|)}