general polishing; added versioning to the document
theory Antiquotesimports "../Base"beginsection {* Useful Document Antiquotations *}text {* {\bf Problem:} How to keep your ML-code inside a document synchronised with the actual code?\smallskip {\bf Solution:} This can be achieved using document antiquotations.\smallskip Document antiquotations can be used for ensuring consistent type-setting of various entities in a document. They can also be used for sophisticated \LaTeX-hacking. If you type @{text "Ctrl-c Ctrl-a h A"} inside ProofGeneral, you obtain a list of all currently available document antiquotations and their options. You obtain the same list on the ML-level by typing @{ML [display,gray] "ThyOutput.print_antiquotations ()"} Below we give the code for two additional antiquotations that can be used to typeset ML-code and also to check whether the given code actually compiles. This provides a sanity check for the code and also allows one to keep documents in sync with other code, for example Isabelle. We first describe the antiquotation @{text "ML_checked"} with the syntax: @{text [display] "@{ML_checked \"a_piece_of_code\"}"} The code is checked by sending the ML-expression @{text [quotes] "val _ = a_piece_of_code"} to the ML-compiler (i.e.~the function @{ML "ML_Context.eval_in"} in Line 4 below). The complete code of the antiquotation is as follows:*}ML%linenosgray{*fun ml_val code_txt = "val _ = " ^ code_txtfun output_ml src ctxt code_txt = (ML_Context.eval_in (SOME ctxt) false Position.none (ml_val code_txt); ThyOutput.output_list (fn _ => fn s => Pretty.str s) src ctxt (space_explode "\n" code_txt))val _ = ThyOutput.add_commands [("ML_checked", ThyOutput.args (Scan.lift Args.name) output_ml)]*}text {* Note that the parser @{ML "(Scan.lift Args.name)"} in line 9 parses a string, in this case the code given as argument. As mentioned before, this argument is sent to the ML-compiler in the line 4 using the function @{ML ml_val}, which constructs the appropriate ML-expression. If the code is ``approved'' by the compiler, then the output function @{ML "ThyOutput.output_list (fn _ => fn s => Pretty.str s)"} in the next line pretty prints the code. This function expects that the code is a list of strings where each string correspond to a line in the output. Therefore the use of @{ML "(space_explode \"\\n\" txt)" for txt} which produces this list according to linebreaks. There are a number of options for antiquotations that are observed by @{ML ThyOutput.output_list} when printing the code (including @{text "[display]"}, @{text "[quotes]"} and @{text "[source]"}). \begin{readmore} For more information about options of antiquotations see \rsccite{sec:antiq}). \end{readmore} Since we used the argument @{ML "Position.none"}, the compiler cannot give specific information about the line number, in case an error is detected. We can improve the code above slightly by writing *}ML%linenosgray{*fun output_ml src ctxt (code_txt,pos) = (ML_Context.eval_in (SOME ctxt) false pos (ml_val code_txt); ThyOutput.output_list (fn _ => fn s => Pretty.str s) src ctxt (space_explode "\n" code_txt))val _ = ThyOutput.add_commands [("ML_checked", ThyOutput.args (Scan.lift (OuterParse.position Args.name)) output_ml)] *}text {* where in Lines 1 and 2 the positional information is properly treated. (FIXME: say something about OuterParse.position) We can now write in a document @{text "@{ML_checked \"2 + 3\"}"} in order to obtain @{ML_checked "2 + 3"} and be sure that this code compiles until somebody changes the definition of \mbox{@{ML "(op +)"}}. The second antiquotation we describe extends the first by allowing also to give a pattern that specifies what the result of the ML-code should be and to check the consistency of the actual result with the given pattern. For this we are going to implement the antiquotation @{text [display] "@{ML_resp \"a_piece_of_code\" \"pattern\"}"} To add some convenience and also to deal with large outputs, the user can give a partial specification by giving the abbreviation @{text [quotes] "\<dots>"}. For example @{text "(\<dots>,\<dots>)"} for a pair. Whereas in the antiquotation @{text "@{ML_checked \"piece_of_code\"}"} above, we have sent the expression @{text [quotes] "val _ = piece_of_code"} to the compiler, in the second the wildcard @{text "_"} we will be replaced by a proper pattern. To do this we need to replace the @{text [quotes] "\<dots>"} by @{text [quotes] "_"} before sending the code to the compiler. The following function will do this:*}ML{*fun ml_pat (code_txt, pat) = let val pat' = implode (map (fn "\<dots>" => "_" | s => s) (Symbol.explode pat)) in "val " ^ pat' ^ " = " ^ code_txt end*}text {* Next we like to add a response indicator to the result using:*}ML{*fun add_resp_indicator pat = map (fn s => "> " ^ s) (space_explode "\n" pat) *}text {* The rest of the code of the antiquotation is*}ML{*fun output_ml_resp src ctxt ((code_txt,pat),pos) = (ML_Context.eval_in (SOME ctxt) false pos (ml_pat (code_txt,pat)); let val output = (space_explode "\n" code_txt) @ (add_resp_indicator pat) in ThyOutput.output_list (fn _ => fn s => Pretty.str s) src ctxt output end)val _ = ThyOutput.add_commands [("ML_resp", ThyOutput.args (Scan.lift (OuterParse.position (Args.name -- Args.name))) output_ml_resp)]*}text {* This extended antiquotation allows us to write @{text [display] "@{ML_resp [display] \"true andalso false\" \"false\"}"} to obtain @{ML_resp [display] "true andalso false" "false"} or @{text [display] "@{ML_resp [display] \"let val i = 3 in (i * i,\"foo\") end\" \"(9,\<dots>)\"}"} to obtain @{ML_resp [display] "let val i = 3 in (i * i,\"foo\") end" "(9,\<dots>)"} In both cases, the check by the compiler ensures that code and result match. A limitation of this antiquotation, however, is that the hints can only be given in case they can be constructed as a pattern. This excludes values that are abstract datatypes, like theorems or cterms.*}end