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