theory Antiquotes

imports "../Appendix"

begin

section \<open>Useful Document Antiquotations\label{rec:docantiquotations}\<close>

text \<open>

  {\bf Problem:} 

  How to keep your ML-code inside a document synchronised with the actual code?\smallskip

  {\bf Solution:} This can be achieved with 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 on the Isabelle level

\<close>

print_antiquotations

text \<open>

  you obtain a list of all currently available document antiquotations and

  their options.  

  Below we will give the code for two additional document

  antiquotations both of which are intended to typeset ML-code. The crucial point

  of these document antiquotations is that they not just print the ML-code, but also 

  check whether it compiles. This will provide a sanity check for the code

  and also allows you to keep documents in sync with other code, for example

  Isabelle.

  We first describe the antiquotation \<open>ML_checked\<close> with the syntax:

  @{text [display] \<open>@{ML_checked "a_piece_of_code"}\<close>}

  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 \<open>ML_Context.eval_source_in\<close>} in Line 7 below). The complete code of the

  document antiquotation is as follows:

\<close>

ML \<open>Input.pos_of\<close>

ML%linenosgray\<open>fun ml_enclose bg en source =

  ML_Lex.read bg @ ML_Lex.read_source source @ ML_Lex.read en;\<close>

ML%linenosgray\<open>fun ml_val code_txt = (ml_enclose "val _ = " "" code_txt)

fun output_ml ctxt code_txt =

let

in 

   Pretty.str (fst (Input.source_content code_txt))

end

setup \<open>ml_checked_setup\<close>

text \<open>

  The parser @{ML \<open>(Scan.lift Args.name)\<close>} in Line 7 parses a string, in this

  case the code, and then calls the function @{ML output_ml}. As mentioned

  before, the parsed code is sent to the ML-compiler in Line 4 using the

  function @{ML ml_val}, which constructs the appropriate ML-expression, and

  using @{ML \<open>eval_in\<close> in ML_Context}, which calls the compiler.  If the code is

  ``approved'' by the compiler, then the output function @{ML \<open>output\<close> in

  Document_Antiquotation} in the next line pretty prints the code. This function expects

  that the code is a list of (pretty)strings where each string correspond to a

  line in the output. Therefore the use of @{ML \<open>(space_explode "\\n" txt)\<close>

  for txt} which produces such a list according to linebreaks.  There are a

  number of options for antiquotations that are observed by the function 

  @{ML \<open>output\<close> in Document_Antiquotation} when printing the code (including \<open>[display]\<close> 

  and \<open>[quotes]\<close>). The function @{ML \<open>antiquotation_raw\<close> in Thy_Output} in 

  Line 7 sets up the new document antiquotation.

  \begin{readmore}

  For more information about options of document antiquotations see \rsccite{sec:antiq}).

  \end{readmore}

  Since we used the argument @{ML \<open>Position.none\<close>}, 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 

\<close>

text \<open>

  where in Lines 1 and 2 the positional information is properly treated. The

  parser @{ML Parse.position} encodes the positional information in the 

  result.

  We can now write \<open>@{ML_checked2 "2 + 3"}\<close> in a document in order to

  obtain @{ML_checked "2 + 3"} and be sure that this code compiles until

  somebody changes the definition of addition.

  The second document antiquotation we describe extends the first by a pattern

  that specifies what the result of the ML-code should be and checks the

  consistency of the actual result with the given pattern. For this we are

  going to implement the document antiquotation:

  @{text [display] \<open>@{ML_resp "a_piece_of_code" "a_pattern"}\<close>}

  To add some convenience and also to deal with large outputs, the user can

  give a partial specification by using ellipses. For example \<open>(\<dots>, \<dots>)\<close>

  for specifying a pair.  In order to check consistency between the pattern

  and the output of the code, we have to change the ML-expression that is sent 

  to the compiler: in \<open>ML_checked2\<close> we sent the expression @{text [quotes]

  "val _ = a_piece_of_code"} to the compiler; now the wildcard \<open>_\<close>

  must be be replaced by the given pattern. However, we have to remove all

  ellipses from it and replace them by @{text [quotes] "_"}. The following 

  function will do this:

\<close>

ML%linenosgray\<open>fun ml_pat pat code =

text \<open>

  Next we add a response indicator to the result using:

\<close>

ML %grayML\<open>fun add_resp pat = map (fn s => "> " ^ s) pat\<close>

text \<open>

  The rest of the code of \<open>ML_resp\<close> is: 

\<close>

ML %linenosgray\<open>

fun output_ml_resp ctxt (code_txt, pat) =

let

  val code = space_explode "\n" (fst (Input.source_content code_txt))

  val resp = add_resp (space_explode "\n" (fst (Input.source_content pat)))

in 

   Pretty.str (cat_lines (code @ resp))

end

\<close>

setup \<open>ml_response_setup\<close>

(* FIXME *)

text \<open>

  In comparison with \<open>ML_checked\<close>, we only changed the line about 

  the compiler (Line~2), the lines about

  the output (Lines 4 to 7) and the parser in the setup (Line 11). Now 

  you can write

  @{text [display] \<open>@{ML_resp [display] "true andalso false" "false"}\<close>}

  to obtain

  @{ML_resp [display] "true andalso false" "false"} 

  or 

  @{text [display] \<open>@{ML_resp [display] "let val i = 3 in (i * i, "foo") end" "(9, \<dots>)"}\<close>}

  to obtain

  @{ML_resp [display] "let val i = 3 in (i * i, \"foo\") end" "(9, _)"} 

  In both cases, the check by the compiler ensures that code and result

  match. A limitation of this document antiquotation, however, is that the

  pattern can only be given for values that can be constructed. This excludes

  values that are abstract datatypes, like @{ML_type thm}s and @{ML_type cterm}s.

\<close>

end