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ocaml-camlp5-doc-5.12-1mdv2010.0.i586.rpm

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  <h1>- <a href="http://pauillac.inria.fr/~ddr/camlp5">Camlp5</a> -</h1>
  <p class="subtitle">Version 5.11</p>
  <ul>
    <li><a href="index.html">Introduction</a></li>
    <li><a href="strict.html">Transitional and Strict</a></li>
    <li><a href="ptools.html">Parsing and printing tools</a></li>
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    <li>Parsing tools
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<h1 class="top">Syntax tree quotations in user syntax</h1>

<p>The quotation kit "<tt>q_ast.cmo</tt>" allows to use syntax tree
  quotations in user syntax. It fully works only in "strict" mode. In
  "transitional" mode, there is no way to use antiquotations, which
  restricts its utility.</p>

<p>If this kit is loaded, when a quotation of syntax tree is found,
  the current OCaml language parser is called. Then, the resulting
  tree is reified (except the antiquotations) to represent <em>the
  syntax tree of the syntax tree</em>.</p>

<h2 id="a:Antiquotations">Antiquotations</h2>

<p>The OCaml langage parser used, and its possible extensions, must
  have been built to allow the places of the antiquotations. The
  symbols enclosed by the meta-symbol "<tt>V</tt>" (see the chapter
  about <a href="grammars.html">extensible grammars</a>, section
  "symbols"), define where antiquotations can take place.</p>

<p>There is no need to specify antiquotations for the main types
  defined in the AST tree module ("<tt>MLast</tt>"): "<tt>expr</tt>",
  "<tt>patt</tt>", "<tt>expr</tt>", "<tt>str_item</tt>",
  "<tt>sig_item</tt>", and so on. All syntax parts of these types are
  automatically antiquotable.</p>

<p>For example, in Camlp5 sources, the grammar rule defining the
  "let..in" statement is:</p>

<pre>
   "let"; r = V (FLAG "rec") "flag" "opt";
    l = V (LIST1 let_binding SEP "and"); "in"; x = expr
</pre>

<p>All symbols of these rules, except the keywords, are antiquotable:</p>

<ul>
  <li>The "rec" flag, because enclosed by the "V" meta symbol. The two
    strings which follow it gives the possible antiquotation kinds:
    "flag" (the normal antiquotation kind) and "opt" (kept by backward
    compatibility, but not recommended). It is therefore possible to
    antiquote it as: "<tt>$flag:...$</tt>" or "<tt>$opt:...$</tt>"
    where the "<tt>...</tt>" is an expression or a pattern depending
    on the position of the enclosing quotation</li>
  <li>The binding list is also antiquotable, since it is also enclosed
    by the "V" meta symbol. Its antiquotation kind is "list" (the
    default when the meta symbol parameter is a list). It is therefore
    possible to write "<tt>$list:...$</tt>" at the place of the
    binding list.</li>
  <li>The expression after the "in" is also antiquotable, because it
    belongs to the main types defined in the module "<tt>MLast</tt>".</li>
</ul>

<p>In that example, the variable "<tt>r</tt>" is of type "<tt>Ploc.vala
  bool</tt>", the variable "<tt>r</tt>" of type "<tt>Ploc.vala (list
  (patt * expr))</tt>" and the variable "<tt>x</tt>" of type
  "<tt>MLast.expr</tt>".</p>

<p>... to be completed ...</p>

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      Daniel de Rauglaudre (INRIA)</em></div>

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