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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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+
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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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  You obtain the same list on the ML-level by typing+
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+
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  @{ML [display,gray] "ThyOutput.print_antiquotations ()"}+
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+
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  Below we give the code for two additional document antiquotations that can+
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  be used to typeset ML-code and also to check whether the given code actually+
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  compiles. This provides a sanity check for the code and also allows one to+
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  keep documents 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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  document antiquotation is as follows:+
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+
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*}+
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+
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ML%linenosgray{*fun ml_val code_txt = "val _ = " ^ code_txt+
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+
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fun output_ml {context = 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 (map Pretty.str (space_explode "\n" code_txt)))+
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+
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val _ = ThyOutput.antiquotation "ML_checked" (Scan.lift Args.name) output_ml*}+
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+
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text {*+
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  The parser @{ML "(Scan.lift Args.name)"} in line 9 parses a string, in this+
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  case the code. As mentioned before, the code is sent to the ML-compiler in+
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  the line 4 using the function @{ML ml_val}, which constructs the appropriate+
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  ML-expression.  If the code is ``approved'' by the compiler, then the output+
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  function @{ML "ThyOutput.output"} in the next line pretty prints the+
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  code. This function expects that the code is a list of (pretty)strings where+
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  each string correspond to a line in the output. Therefore the use of @{ML+
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  "(space_explode \"\\n\" txt)" for txt} which produces this list according to+
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  linebreaks.  There are a number of options for antiquotations that are+
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  observed by @{ML ThyOutput.output} when printing the code (including @{text+
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  "[display]"} and @{text "[quotes]"}). Line 7 sets up the new document+
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  antiquotation.+
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+
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+
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  \begin{readmore}+
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  For more information about options of document 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%linenosgray{*fun output_ml {context = 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 (map Pretty.str (space_explode "\n" code_txt)))+
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+
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val _ = ThyOutput.antiquotation "ML_checked"+
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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. The+
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  parser @{ML OuterParse.position} encodes the positional information in the +
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  result.+
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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 document antiquotation we describe extends the first by a pattern+
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  that specifies what the result of the ML-code should be and check the+
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  consistency of the actual result with the given pattern. For this we are+
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  going to implement the document antiquotation+
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+
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  +
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  @{text [display] "@{ML_resp \"a_piece_of_code\" \"a_pattern\"}"}+
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  +
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  To add some convenience and also to deal with large outputs, the user can+
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  give a partial specification inside the pattern by giving abbreviations of+
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  the form @{text [quotes] "\<dots>"}. For example @{text "(\<dots>, \<dots>)"} for specifying a+
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  pair.+
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+
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  In the document antiquotation @{text "@{ML_checked \"piece_of_code\"}"}+
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  above we have sent the expression @{text [quotes] "val _ = piece_of_code"}+
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  to the compiler, now instead the wildcard @{text "_"} we will be replaced by+
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  the given pattern. To do this we need to replace in the input the @{text+
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  [quotes] "\<dots>"} by @{text [quotes] "_"} before sending the code to the+
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  compiler. The following function will do this:+
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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 pat = map (fn s => "> " ^ s) pat*}+
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+
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text {* +
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  The rest of the code of the document antiquotation is+
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*}+
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+
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ML{*fun output_ml_resp {context = 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 output1 = space_explode "\n" code_txt +
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     val output2 = add_resp (space_explode "\n" pat)+
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   in +
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     ThyOutput.output (map Pretty.str (output1 @ output2)) +
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   end)+
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+
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val _ = ThyOutput.antiquotation "ML_resp" +
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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 document 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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+
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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+
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  match. A limitation of this document antiquotation, however, is that the+
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  pattern can only be given for values that can be constructed. This excludes+
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  values that are abstract datatypes, like @{ML_type thm}s and @{ML_type cterm}s.+
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+
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*}+
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end+
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