diff -r 2775062fd3a9 -r 2f4684e2ea95 doc-src/Codegen/Thy/document/Adaption.tex --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/doc-src/Codegen/Thy/document/Adaption.tex Tue Mar 03 11:00:51 2009 +0100 @@ -0,0 +1,679 @@ +% +\begin{isabellebody}% +\def\isabellecontext{Adaption}% +% +\isadelimtheory +% +\endisadelimtheory +% +\isatagtheory +\isacommand{theory}\isamarkupfalse% +\ Adaption\isanewline +\isakeyword{imports}\ Setup\isanewline +\isakeyword{begin}% +\endisatagtheory +{\isafoldtheory}% +% +\isadelimtheory +\isanewline +% +\endisadelimtheory +% +\isadeliminvisible +\isanewline +% +\endisadeliminvisible +% +\isataginvisible +\isacommand{setup}\isamarkupfalse% +\ {\isacharverbatimopen}\ Code{\isacharunderscore}Target{\isachardot}extend{\isacharunderscore}target\ {\isacharparenleft}{\isachardoublequote}{\isasymSML}{\isachardoublequote}{\isacharcomma}\ {\isacharparenleft}{\isachardoublequote}SML{\isachardoublequote}{\isacharcomma}\ K\ I{\isacharparenright}{\isacharparenright}\ {\isacharverbatimclose}% +\endisataginvisible +{\isafoldinvisible}% +% +\isadeliminvisible +% +\endisadeliminvisible +% +\isamarkupsection{Adaption to target languages \label{sec:adaption}% +} +\isamarkuptrue% +% +\isamarkupsubsection{Adapting code generation% +} +\isamarkuptrue% +% +\begin{isamarkuptext}% +The aspects of code generation introduced so far have two aspects + in common: + + \begin{itemize} + \item They act uniformly, without reference to a specific + target language. + \item They are \emph{safe} in the sense that as long as you trust + the code generator meta theory and implementation, you cannot + produce programs that yield results which are not derivable + in the logic. + \end{itemize} + + \noindent In this section we will introduce means to \emph{adapt} the serialiser + to a specific target language, i.e.~to print program fragments + in a way which accommodates \qt{already existing} ingredients of + a target language environment, for three reasons: + + \begin{itemize} + \item improving readability and aesthetics of generated code + \item gaining efficiency + \item interface with language parts which have no direct counterpart + in \isa{HOL} (say, imperative data structures) + \end{itemize} + + \noindent Generally, you should avoid using those features yourself + \emph{at any cost}: + + \begin{itemize} + \item The safe configuration methods act uniformly on every target language, + whereas for adaption you have to treat each target language separate. + \item Application is extremely tedious since there is no abstraction + which would allow for a static check, making it easy to produce garbage. + \item More or less subtle errors can be introduced unconsciously. + \end{itemize} + + \noindent However, even if you ought refrain from setting up adaption + yourself, already the \isa{HOL} comes with some reasonable default + adaptions (say, using target language list syntax). There also some + common adaption cases which you can setup by importing particular + library theories. In order to understand these, we provide some clues here; + these however are not supposed to replace a careful study of the sources.% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isamarkupsubsection{The adaption principle% +} +\isamarkuptrue% +% +\begin{isamarkuptext}% +The following figure illustrates what \qt{adaption} is conceptually + supposed to be: + + \begin{figure}[here] + \begin{tikzpicture}[scale = 0.5] + \tikzstyle water=[color = blue, thick] + \tikzstyle ice=[color = black, very thick, cap = round, join = round, fill = white] + \tikzstyle process=[color = green, semithick, ->] + \tikzstyle adaption=[color = red, semithick, ->] + \tikzstyle target=[color = black] + \foreach \x in {0, ..., 24} + \draw[style=water] (\x, 0.25) sin + (0.25, 0.25) cos + (0.25, -0.25) sin + + (0.25, -0.25) cos + (0.25, 0.25); + \draw[style=ice] (1, 0) -- + (3, 6) node[above, fill=white] {logic} -- (5, 0) -- cycle; + \draw[style=ice] (9, 0) -- + (11, 6) node[above, fill=white] {intermediate language} -- (13, 0) -- cycle; + \draw[style=ice] (15, -6) -- + (19, 6) node[above, fill=white] {target language} -- (23, -6) -- cycle; + \draw[style=process] + (3.5, 3) .. controls (7, 5) .. node[fill=white] {translation} (10.5, 3); + \draw[style=process] + (11.5, 3) .. controls (15, 5) .. node[fill=white] (serialisation) {serialisation} (18.5, 3); + \node (adaption) at (11, -2) [style=adaption] {adaption}; + \node at (19, 3) [rotate=90] {generated}; + \node at (19.5, -5) {language}; + \node at (19.5, -3) {library}; + \node (includes) at (19.5, -1) {includes}; + \node (reserved) at (16.5, -3) [rotate=72] {reserved}; % proper 71.57 + \draw[style=process] + (includes) -- (serialisation); + \draw[style=process] + (reserved) -- (serialisation); + \draw[style=adaption] + (adaption) -- (serialisation); + \draw[style=adaption] + (adaption) -- (includes); + \draw[style=adaption] + (adaption) -- (reserved); + \end{tikzpicture} + \caption{The adaption principle} + \label{fig:adaption} + \end{figure} + + \noindent In the tame view, code generation acts as broker between + \isa{logic}, \isa{intermediate\ language} and + \isa{target\ language} by means of \isa{translation} and + \isa{serialisation}; for the latter, the serialiser has to observe + the structure of the \isa{language} itself plus some \isa{reserved} + keywords which have to be avoided for generated code. + However, if you consider \isa{adaption} mechanisms, the code generated + by the serializer is just the tip of the iceberg: + + \begin{itemize} + \item \isa{serialisation} can be \emph{parametrised} such that + logical entities are mapped to target-specific ones + (e.g. target-specific list syntax, + see also \secref{sec:adaption_mechanisms}) + \item Such parametrisations can involve references to a + target-specific standard \isa{library} (e.g. using + the \isa{Haskell} \verb|Maybe| type instead + of the \isa{HOL} \isa{option} type); + if such are used, the corresponding identifiers + (in our example, \verb|Maybe|, \verb|Nothing| + and \verb|Just|) also have to be considered \isa{reserved}. + \item Even more, the user can enrich the library of the + target-language by providing code snippets + (\qt{\isa{includes}}) which are prepended to + any generated code (see \secref{sec:include}); this typically + also involves further \isa{reserved} identifiers. + \end{itemize} + + \noindent As figure \ref{fig:adaption} illustrates, all these adaption mechanisms + have to act consistently; it is at the discretion of the user + to take care for this.% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isamarkupsubsection{Common adaption patterns% +} +\isamarkuptrue% +% +\begin{isamarkuptext}% +The \hyperlink{theory.HOL}{\mbox{\isa{HOL}}} \hyperlink{theory.Main}{\mbox{\isa{Main}}} theory already provides a code + generator setup + which should be suitable for most applications. Common extensions + and modifications are available by certain theories of the \isa{HOL} + library; beside being useful in applications, they may serve + as a tutorial for customising the code generator setup (see below + \secref{sec:adaption_mechanisms}). + + \begin{description} + + \item[\hyperlink{theory.Code-Integer}{\mbox{\isa{Code{\isacharunderscore}Integer}}}] represents \isa{HOL} integers by big + integer literals in target languages. + \item[\hyperlink{theory.Code-Char}{\mbox{\isa{Code{\isacharunderscore}Char}}}] represents \isa{HOL} characters by + character literals in target languages. + \item[\hyperlink{theory.Code-Char-chr}{\mbox{\isa{Code{\isacharunderscore}Char{\isacharunderscore}chr}}}] like \isa{Code{\isacharunderscore}Char}, + but also offers treatment of character codes; includes + \hyperlink{theory.Code-Char}{\mbox{\isa{Code{\isacharunderscore}Char}}}. + \item[\hyperlink{theory.Efficient-Nat}{\mbox{\isa{Efficient{\isacharunderscore}Nat}}}] \label{eff_nat} implements natural numbers by integers, + which in general will result in higher efficiency; pattern + matching with \isa{{\isadigit{0}}} / \isa{Suc} + is eliminated; includes \hyperlink{theory.Code-Integer}{\mbox{\isa{Code{\isacharunderscore}Integer}}} + and \hyperlink{theory.Code-Index}{\mbox{\isa{Code{\isacharunderscore}Index}}}. + \item[\hyperlink{theory.Code-Index}{\mbox{\isa{Code{\isacharunderscore}Index}}}] provides an additional datatype + \isa{index} which is mapped to target-language built-in integers. + Useful for code setups which involve e.g. indexing of + target-language arrays. + \item[\hyperlink{theory.Code-Message}{\mbox{\isa{Code{\isacharunderscore}Message}}}] provides an additional datatype + \isa{message{\isacharunderscore}string} which is isomorphic to strings; + \isa{message{\isacharunderscore}string}s are mapped to target-language strings. + Useful for code setups which involve e.g. printing (error) messages. + + \end{description} + + \begin{warn} + When importing any of these theories, they should form the last + items in an import list. Since these theories adapt the + code generator setup in a non-conservative fashion, + strange effects may occur otherwise. + \end{warn}% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isamarkupsubsection{Parametrising serialisation \label{sec:adaption_mechanisms}% +} +\isamarkuptrue% +% +\begin{isamarkuptext}% +Consider the following function and its corresponding + SML code:% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isadelimquote +% +\endisadelimquote +% +\isatagquote +\isacommand{primrec}\isamarkupfalse% +\ in{\isacharunderscore}interval\ {\isacharcolon}{\isacharcolon}\ {\isachardoublequoteopen}nat\ {\isasymtimes}\ nat\ {\isasymRightarrow}\ nat\ {\isasymRightarrow}\ bool{\isachardoublequoteclose}\ \isakeyword{where}\isanewline +\ \ {\isachardoublequoteopen}in{\isacharunderscore}interval\ {\isacharparenleft}k{\isacharcomma}\ l{\isacharparenright}\ n\ {\isasymlongleftrightarrow}\ k\ {\isasymle}\ n\ {\isasymand}\ n\ {\isasymle}\ l{\isachardoublequoteclose}% +\endisatagquote +{\isafoldquote}% +% +\isadelimquote +% +\endisadelimquote +% +\isadeliminvisible +% +\endisadeliminvisible +% +\isataginvisible +% +\endisataginvisible +{\isafoldinvisible}% +% +\isadeliminvisible +% +\endisadeliminvisible +% +\isadelimquote +% +\endisadelimquote +% +\isatagquote +% +\begin{isamarkuptext}% +\isatypewriter% +\noindent% +\hspace*{0pt}structure Example = \\ +\hspace*{0pt}struct\\ +\hspace*{0pt}\\ +\hspace*{0pt}datatype nat = Zero{\char95}nat | Suc of nat;\\ +\hspace*{0pt}\\ +\hspace*{0pt}datatype boola = True | False;\\ +\hspace*{0pt}\\ +\hspace*{0pt}fun anda x True = x\\ +\hspace*{0pt} ~| anda x False = False\\ +\hspace*{0pt} ~| anda True x = x\\ +\hspace*{0pt} ~| anda False x = False;\\ +\hspace*{0pt}\\ +\hspace*{0pt}fun less{\char95}nat m (Suc n) = less{\char95}eq{\char95}nat m n\\ +\hspace*{0pt} ~| less{\char95}nat n Zero{\char95}nat = False\\ +\hspace*{0pt}and less{\char95}eq{\char95}nat (Suc m) n = less{\char95}nat m n\\ +\hspace*{0pt} ~| less{\char95}eq{\char95}nat Zero{\char95}nat n = True;\\ +\hspace*{0pt}\\ +\hspace*{0pt}fun in{\char95}interval (k,~l) n = anda (less{\char95}eq{\char95}nat k n) (less{\char95}eq{\char95}nat n l);\\ +\hspace*{0pt}\\ +\hspace*{0pt}end;~(*struct Example*)% +\end{isamarkuptext}% +\isamarkuptrue% +% +\endisatagquote +{\isafoldquote}% +% +\isadelimquote +% +\endisadelimquote +% +\begin{isamarkuptext}% +\noindent Though this is correct code, it is a little bit unsatisfactory: + boolean values and operators are materialised as distinguished + entities with have nothing to do with the SML-built-in notion + of \qt{bool}. This results in less readable code; + additionally, eager evaluation may cause programs to + loop or break which would perfectly terminate when + the existing SML \verb|bool| would be used. To map + the HOL \isa{bool} on SML \verb|bool|, we may use + \qn{custom serialisations}:% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isadelimquotett +% +\endisadelimquotett +% +\isatagquotett +\isacommand{code{\isacharunderscore}type}\isamarkupfalse% +\ bool\isanewline +\ \ {\isacharparenleft}SML\ {\isachardoublequoteopen}bool{\isachardoublequoteclose}{\isacharparenright}\isanewline +\isacommand{code{\isacharunderscore}const}\isamarkupfalse% +\ True\ \isakeyword{and}\ False\ \isakeyword{and}\ {\isachardoublequoteopen}op\ {\isasymand}{\isachardoublequoteclose}\isanewline +\ \ {\isacharparenleft}SML\ {\isachardoublequoteopen}true{\isachardoublequoteclose}\ \isakeyword{and}\ {\isachardoublequoteopen}false{\isachardoublequoteclose}\ \isakeyword{and}\ {\isachardoublequoteopen}{\isacharunderscore}\ andalso\ {\isacharunderscore}{\isachardoublequoteclose}{\isacharparenright}% +\endisatagquotett +{\isafoldquotett}% +% +\isadelimquotett +% +\endisadelimquotett +% +\begin{isamarkuptext}% +\noindent The \hyperlink{command.code-type}{\mbox{\isa{\isacommand{code{\isacharunderscore}type}}}} command takes a type constructor + as arguments together with a list of custom serialisations. + Each custom serialisation starts with a target language + identifier followed by an expression, which during + code serialisation is inserted whenever the type constructor + would occur. For constants, \hyperlink{command.code-const}{\mbox{\isa{\isacommand{code{\isacharunderscore}const}}}} implements + the corresponding mechanism. Each ``\verb|_|'' in + a serialisation expression is treated as a placeholder + for the type constructor's (the constant's) arguments.% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isadelimquote +% +\endisadelimquote +% +\isatagquote +% +\begin{isamarkuptext}% +\isatypewriter% +\noindent% +\hspace*{0pt}structure Example = \\ +\hspace*{0pt}struct\\ +\hspace*{0pt}\\ +\hspace*{0pt}datatype nat = Zero{\char95}nat | Suc of nat;\\ +\hspace*{0pt}\\ +\hspace*{0pt}fun less{\char95}nat m (Suc n) = less{\char95}eq{\char95}nat m n\\ +\hspace*{0pt} ~| less{\char95}nat n Zero{\char95}nat = false\\ +\hspace*{0pt}and less{\char95}eq{\char95}nat (Suc m) n = less{\char95}nat m n\\ +\hspace*{0pt} ~| less{\char95}eq{\char95}nat Zero{\char95}nat n = true;\\ +\hspace*{0pt}\\ +\hspace*{0pt}fun in{\char95}interval (k,~l) n = (less{\char95}eq{\char95}nat k n) andalso (less{\char95}eq{\char95}nat n l);\\ +\hspace*{0pt}\\ +\hspace*{0pt}end;~(*struct Example*)% +\end{isamarkuptext}% +\isamarkuptrue% +% +\endisatagquote +{\isafoldquote}% +% +\isadelimquote +% +\endisadelimquote +% +\begin{isamarkuptext}% +\noindent This still is not perfect: the parentheses + around the \qt{andalso} expression are superfluous. + Though the serialiser + by no means attempts to imitate the rich Isabelle syntax + framework, it provides some common idioms, notably + associative infixes with precedences which may be used here:% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isadelimquotett +% +\endisadelimquotett +% +\isatagquotett +\isacommand{code{\isacharunderscore}const}\isamarkupfalse% +\ {\isachardoublequoteopen}op\ {\isasymand}{\isachardoublequoteclose}\isanewline +\ \ {\isacharparenleft}SML\ \isakeyword{infixl}\ {\isadigit{1}}\ {\isachardoublequoteopen}andalso{\isachardoublequoteclose}{\isacharparenright}% +\endisatagquotett +{\isafoldquotett}% +% +\isadelimquotett +% +\endisadelimquotett +% +\isadelimquote +% +\endisadelimquote +% +\isatagquote +% +\begin{isamarkuptext}% +\isatypewriter% +\noindent% +\hspace*{0pt}structure Example = \\ +\hspace*{0pt}struct\\ +\hspace*{0pt}\\ +\hspace*{0pt}datatype nat = Zero{\char95}nat | Suc of nat;\\ +\hspace*{0pt}\\ +\hspace*{0pt}fun less{\char95}nat m (Suc n) = less{\char95}eq{\char95}nat m n\\ +\hspace*{0pt} ~| less{\char95}nat n Zero{\char95}nat = false\\ +\hspace*{0pt}and less{\char95}eq{\char95}nat (Suc m) n = less{\char95}nat m n\\ +\hspace*{0pt} ~| less{\char95}eq{\char95}nat Zero{\char95}nat n = true;\\ +\hspace*{0pt}\\ +\hspace*{0pt}fun in{\char95}interval (k,~l) n = less{\char95}eq{\char95}nat k n andalso less{\char95}eq{\char95}nat n l;\\ +\hspace*{0pt}\\ +\hspace*{0pt}end;~(*struct Example*)% +\end{isamarkuptext}% +\isamarkuptrue% +% +\endisatagquote +{\isafoldquote}% +% +\isadelimquote +% +\endisadelimquote +% +\begin{isamarkuptext}% +\noindent The attentive reader may ask how we assert that no generated + code will accidentally overwrite. For this reason the serialiser has + an internal table of identifiers which have to be avoided to be used + for new declarations. Initially, this table typically contains the + keywords of the target language. It can be extended manually, thus avoiding + accidental overwrites, using the \hyperlink{command.code-reserved}{\mbox{\isa{\isacommand{code{\isacharunderscore}reserved}}}} command:% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isadelimquote +% +\endisadelimquote +% +\isatagquote +\isacommand{code{\isacharunderscore}reserved}\isamarkupfalse% +\ {\isachardoublequoteopen}{\isasymSML}{\isachardoublequoteclose}\ bool\ true\ false\ andalso% +\endisatagquote +{\isafoldquote}% +% +\isadelimquote +% +\endisadelimquote +% +\begin{isamarkuptext}% +\noindent Next, we try to map HOL pairs to SML pairs, using the + infix ``\verb|*|'' type constructor and parentheses:% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isadeliminvisible +% +\endisadeliminvisible +% +\isataginvisible +% +\endisataginvisible +{\isafoldinvisible}% +% +\isadeliminvisible +% +\endisadeliminvisible +% +\isadelimquotett +% +\endisadelimquotett +% +\isatagquotett +\isacommand{code{\isacharunderscore}type}\isamarkupfalse% +\ {\isacharasterisk}\isanewline +\ \ {\isacharparenleft}SML\ \isakeyword{infix}\ {\isadigit{2}}\ {\isachardoublequoteopen}{\isacharasterisk}{\isachardoublequoteclose}{\isacharparenright}\isanewline +\isacommand{code{\isacharunderscore}const}\isamarkupfalse% +\ Pair\isanewline +\ \ {\isacharparenleft}SML\ {\isachardoublequoteopen}{\isacharbang}{\isacharparenleft}{\isacharparenleft}{\isacharunderscore}{\isacharparenright}{\isacharcomma}{\isacharslash}\ {\isacharparenleft}{\isacharunderscore}{\isacharparenright}{\isacharparenright}{\isachardoublequoteclose}{\isacharparenright}% +\endisatagquotett +{\isafoldquotett}% +% +\isadelimquotett +% +\endisadelimquotett +% +\begin{isamarkuptext}% +\noindent The initial bang ``\verb|!|'' tells the serialiser + never to put + parentheses around the whole expression (they are already present), + while the parentheses around argument place holders + tell not to put parentheses around the arguments. + The slash ``\verb|/|'' (followed by arbitrary white space) + inserts a space which may be used as a break if necessary + during pretty printing. + + These examples give a glimpse what mechanisms + custom serialisations provide; however their usage + requires careful thinking in order not to introduce + inconsistencies -- or, in other words: + custom serialisations are completely axiomatic. + + A further noteworthy details is that any special + character in a custom serialisation may be quoted + using ``\verb|'|''; thus, in + ``\verb|fn '_ => _|'' the first + ``\verb|_|'' is a proper underscore while the + second ``\verb|_|'' is a placeholder.% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isamarkupsubsection{\isa{Haskell} serialisation% +} +\isamarkuptrue% +% +\begin{isamarkuptext}% +For convenience, the default + \isa{HOL} setup for \isa{Haskell} maps the \isa{eq} class to + its counterpart in \isa{Haskell}, giving custom serialisations + for the class \isa{eq} (by command \hyperlink{command.code-class}{\mbox{\isa{\isacommand{code{\isacharunderscore}class}}}}) and its operation + \isa{eq{\isacharunderscore}class{\isachardot}eq}% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isadelimquotett +% +\endisadelimquotett +% +\isatagquotett +\isacommand{code{\isacharunderscore}class}\isamarkupfalse% +\ eq\isanewline +\ \ {\isacharparenleft}Haskell\ {\isachardoublequoteopen}Eq{\isachardoublequoteclose}{\isacharparenright}\isanewline +\isanewline +\isacommand{code{\isacharunderscore}const}\isamarkupfalse% +\ {\isachardoublequoteopen}op\ {\isacharequal}{\isachardoublequoteclose}\isanewline +\ \ {\isacharparenleft}Haskell\ \isakeyword{infixl}\ {\isadigit{4}}\ {\isachardoublequoteopen}{\isacharequal}{\isacharequal}{\isachardoublequoteclose}{\isacharparenright}% +\endisatagquotett +{\isafoldquotett}% +% +\isadelimquotett +% +\endisadelimquotett +% +\begin{isamarkuptext}% +\noindent A problem now occurs whenever a type which + is an instance of \isa{eq} in \isa{HOL} is mapped + on a \isa{Haskell}-built-in type which is also an instance + of \isa{Haskell} \isa{Eq}:% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isadelimquote +% +\endisadelimquote +% +\isatagquote +\isacommand{typedecl}\isamarkupfalse% +\ bar\isanewline +\isanewline +\isacommand{instantiation}\isamarkupfalse% +\ bar\ {\isacharcolon}{\isacharcolon}\ eq\isanewline +\isakeyword{begin}\isanewline +\isanewline +\isacommand{definition}\isamarkupfalse% +\ {\isachardoublequoteopen}eq{\isacharunderscore}class{\isachardot}eq\ {\isacharparenleft}x{\isasymColon}bar{\isacharparenright}\ y\ {\isasymlongleftrightarrow}\ x\ {\isacharequal}\ y{\isachardoublequoteclose}\isanewline +\isanewline +\isacommand{instance}\isamarkupfalse% +\ \isacommand{by}\isamarkupfalse% +\ default\ {\isacharparenleft}simp\ add{\isacharcolon}\ eq{\isacharunderscore}bar{\isacharunderscore}def{\isacharparenright}\isanewline +\isanewline +\isacommand{end}\isamarkupfalse% +% +\endisatagquote +{\isafoldquote}% +% +\isadelimquote +% +\endisadelimquote +\isanewline +% +\isadelimquotett +\isanewline +% +\endisadelimquotett +% +\isatagquotett +\isacommand{code{\isacharunderscore}type}\isamarkupfalse% +\ bar\isanewline +\ \ {\isacharparenleft}Haskell\ {\isachardoublequoteopen}Integer{\isachardoublequoteclose}{\isacharparenright}% +\endisatagquotett +{\isafoldquotett}% +% +\isadelimquotett +% +\endisadelimquotett +% +\begin{isamarkuptext}% +\noindent The code generator would produce + an additional instance, which of course is rejected by the \isa{Haskell} + compiler. + To suppress this additional instance, use + \isa{code{\isacharunderscore}instance}:% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isadelimquotett +% +\endisadelimquotett +% +\isatagquotett +\isacommand{code{\isacharunderscore}instance}\isamarkupfalse% +\ bar\ {\isacharcolon}{\isacharcolon}\ eq\isanewline +\ \ {\isacharparenleft}Haskell\ {\isacharminus}{\isacharparenright}% +\endisatagquotett +{\isafoldquotett}% +% +\isadelimquotett +% +\endisadelimquotett +% +\isamarkupsubsection{Enhancing the target language context \label{sec:include}% +} +\isamarkuptrue% +% +\begin{isamarkuptext}% +In rare cases it is necessary to \emph{enrich} the context of a + target language; this is accomplished using the \hyperlink{command.code-include}{\mbox{\isa{\isacommand{code{\isacharunderscore}include}}}} + command:% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isadelimquotett +% +\endisadelimquotett +% +\isatagquotett +\isacommand{code{\isacharunderscore}include}\isamarkupfalse% +\ Haskell\ {\isachardoublequoteopen}Errno{\isachardoublequoteclose}\isanewline +{\isacharverbatimopen}errno\ i\ {\isacharequal}\ error\ {\isacharparenleft}{\isachardoublequote}Error\ number{\isacharcolon}\ {\isachardoublequote}\ {\isacharplus}{\isacharplus}\ show\ i{\isacharparenright}{\isacharverbatimclose}\isanewline +\isanewline +\isacommand{code{\isacharunderscore}reserved}\isamarkupfalse% +\ Haskell\ Errno% +\endisatagquotett +{\isafoldquotett}% +% +\isadelimquotett +% +\endisadelimquotett +% +\begin{isamarkuptext}% +\noindent Such named \isa{include}s are then prepended to every generated code. + Inspect such code in order to find out how \hyperlink{command.code-include}{\mbox{\isa{\isacommand{code{\isacharunderscore}include}}}} behaves + with respect to a particular target language.% +\end{isamarkuptext}% +\isamarkuptrue% +% +\isadelimtheory +% +\endisadelimtheory +% +\isatagtheory +\isacommand{end}\isamarkupfalse% +% +\endisatagtheory +{\isafoldtheory}% +% +\isadelimtheory +% +\endisadelimtheory +\isanewline +\end{isabellebody}% +%%% Local Variables: +%%% mode: latex +%%% TeX-master: "root" +%%% End: