* Pure/library.ML: several combinators for linear functional transformations;
* Pure/library.ML: canonical list combinators fold, fold_rev, and fold_yield;
* Pure/term.ML: combinators fold_atyps, fold_aterms, fold_term_types, fold_types;
%
\begin{isabellebody}%
\def\isabellecontext{find{\isadigit{2}}}%
\isamarkupfalse%
\isamarkupfalse%
%
\begin{isamarkuptxt}%
\index{finding theorems}\index{searching theorems} In
\S\ref{sec:find}, we introduced Proof General's \pgmenu{Find} button
for finding theorems in the database via pattern matching. If we are
inside a proof, we can be more specific; we can search for introduction,
elimination and destruction rules \emph{with respect to the current goal}.
For this purpose, \pgmenu{Find} provides three aditional search criteria:
\texttt{intro}, \texttt{elim} and \texttt{dest}.
For example, given the goal \begin{isabelle}%
\ {\isadigit{1}}{\isachardot}\ A\ {\isasymand}\ B%
\end{isabelle}
you can click on \pgmenu{Find} and type in the search expression
\texttt{intro}. You will be shown a few rules ending in \isa{{\isasymLongrightarrow}\ {\isacharquery}P\ {\isasymand}\ {\isacharquery}Q},
among them \isa{conjI}\@. You may even discover that
the very theorem you are trying to prove is already in the
database. Given the goal%
\end{isamarkuptxt}%
\isamarkuptrue%
\isamarkupfalse%
\isamarkupfalse%
%
\begin{isamarkuptxt}%
\vspace{-\bigskipamount}
\begin{isabelle}%
\ {\isadigit{1}}{\isachardot}\ A\ {\isasymlongrightarrow}\ A%
\end{isabelle}
the search for \texttt{intro} finds not just \isa{impI}
but also \isa{imp{\isacharunderscore}refl}: \isa{{\isacharquery}P\ {\isasymlongrightarrow}\ {\isacharquery}P}.
As before, search criteria can be combined freely: for example,
\begin{ttbox}
"_ \at\ _" intro
\end{ttbox}
searches for all introduction rules that match the current goal and
mention the \isa{{\isacharat}} function.
Searching for elimination and destruction rules via \texttt{elim} and
\texttt{dest} is analogous to \texttt{intro} but takes the assumptions
into account, too.%
\end{isamarkuptxt}%
\isamarkuptrue%
\isamarkupfalse%
\isamarkupfalse%
\end{isabellebody}%
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