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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.+
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+
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  Below we give the code for two 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 \"expr\"}"}. This+
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  antiquotation takes a piece of code as argument. The argument is checked+
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  by sending the ML-expression @{text [quotes] "val _ = \<dots>"} containing the+
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  given argument to the ML-compiler (i.e.~the function @{ML "ML_Context.eval_in"}+
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  in Line 4 in the code below). The code of @{text "@{ML_checked \"expr\"}"} +
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  is as follows:+
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+
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*}+
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+
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ML %linenumbers {*fun ml_val txt = "val _ = " ^ txt+
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+
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fun output_ml ml src ctxt txt =+
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  (ML_Context.eval_in (SOME ctxt) false Position.none (ml txt); +
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  ThyOutput.output_list (fn _ => fn s => Pretty.str s) src ctxt +
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                                            (space_explode "\n" 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 ml_val))]+
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*}+
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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. This argument is send to the ML-compiler in the line 4.  +
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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. Therefore the @{ML "(space_explode \"\\n\" txt)" for txt} +
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  which produces this list.  There are a number of options for antiquotations+
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  that are observed by @{ML ThyOutput.output_list} when printing the code (for+
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  example @{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 where an error might have occurred. We +
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  can improve this code slightly by writing +
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+
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*}+
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+
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ML %linenumbers {* fun output_ml ml src ctxt (txt,pos) =+
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  (ML_Context.eval_in (SOME ctxt) false pos (ml txt);+
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  ThyOutput.output_list (fn _ => fn s => Pretty.str s) src ctxt +
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                                            (space_explode "\n" 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 ml_val))]+
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*}+
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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 extends the first by allowing also to give+
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  hints what the result of the ML-code is and check the consistency of +
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  the actual result with these hints. For this we use the antiquotation  +
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  @{text "@{ML_response \"expr\" \"pat\"}"}+
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  whose first argument is the ML-code and the second is a pattern specifying+
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  the result. To add some convenience we allow the user to give a partial+
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  specification using @{text "\<dots>"}.+
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+
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  In the antiquotation @{text "@{ML_checked \"expr\"}"} we send the expression +
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  @{text [quotes] "val _ = expr"} to the compiler. Instead of the wildcard+
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  @{text "_"}, we will here use the hints to construct a proper pattern. To+
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  do this we need to replace the @{text "\<dots>"} by @{text "_"} before sending the +
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  code to the compiler. The function +
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+
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*}+
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+
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ML {* +
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fun ml_pat (rhs, pat) =+
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let val pat' = implode (map (fn "\<dots>" => "_" | s => s) (Symbol.explode pat))+
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in "val " ^ pat' ^ " = " ^ rhs end;+
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*}+
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+
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text {* +
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  will construct the pattern that the compiler can use. Next we like to add +
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  a response indicator to the result using:+
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*}+
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+
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+
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ML {*+
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fun add_response_indicator txt =+
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  map (fn s => "> " ^ s) (space_explode "\n" txt)+
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*}+
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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 {*+
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fun output_ml_response ml src ctxt ((lhs,pat),pos) = +
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  (ML_Context.eval_in (SOME ctxt) false pos (ml (lhs,pat));+
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  let val txt = (space_explode "\n" lhs) @ (add_response_indicator pat)+
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  in ThyOutput.output_list (fn _ => fn s => Pretty.str s) src ctxt txt end)+
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+
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val _ = ThyOutput.add_commands+
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 [("ML_response", +
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     ThyOutput.args +
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      (Scan.lift (OuterParse.position (Args.name -- Args.name))) +
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      (output_ml_response ml_pat))]+
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*}+
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+
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text {*+
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  This extended antiquotation allows us to write +
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  @{text [display] "@{ML_response [display] \"true andalso false\" \"false\"}"}+
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  to obtain+
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+
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@{ML_response [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_response [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_response [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 is that the hints can only be given for results that can actually+
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  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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