twig(1) [plan9 man page]

TWIG(1) 						      General Commands Manual							   TWIG(1)

NAME

       twig - tree-manipulation language

SYNOPSIS

       twig [ -sASC ] [ -w suffix ] file.mt

DESCRIPTION

       Twig  converts  a tree-specification scheme consisting of pattern-action rules with associated costs into C functions that can be called to
       manipulate input trees.	The C functions first find a minimum-cost covering of an input tree using a dynamic programming algorithm and then
       execute	the  actions  associated with the patterns used in the covering.  The tree-specification scheme may allow several coverings for an
       input tree, but the dynamic programming algorithm resolves any ambiguities by selecting a cheapest covering.

       The input file containing the tree-specification scheme must have the suffix Twig produces two output files: walker.c,  which  becomes  the
       source file for the tree matcher, and symbols.h, which contains the definitions for the node and label symbols used in the source file.

       To build walker.c, twig uses an internal template file, by default one appropriate for use with fprintf(2).

       The options are

       -A	  Use a template file for ANSI/POSIX source files.

       -C	  Use a template file for files that use libc's print(2) routines.

       -S	  Use a template file for files that use fprintf(2).

       -s	  Do not produce a symbols.h file.

       -w suffix  Use the template file /sys/lib/twig/walker.suffix.

FILES

       /sys/lib/twig
	      System area for template files.

SOURCE

       /sys/src/cmd/twig

SEE ALSO

       yacc(1)
       S. W. K. Tjiang, ``The Twig Reference Manual'', Computing Science Technical Report No. 120, AT&T Bell Laboratories, Murray Hill, N.J.
       A. V. Aho, M. Ganapathi, and S. W. K. Tjiang, ``Code generation using tree matching and dynamic programming.''

BUGS

       When tree matching fails, the debugging output is cryptic.

																	   TWIG(1)

xmerl_xs(3erl)						     Erlang Module Definition						    xmerl_xs(3erl)

NAME

       xmerl_xs -
	      Erlang has similarities to XSLT since both languages
	    have a functional programming approach.

DESCRIPTION

       Erlang has similarities to XSLT since both languages have a functional programming approach. Using xmerl_xpath it is possible to write XSLT
       like transforms in Erlang.

       XSLT stylesheets are often used when transforming XML documents, to other XML documents or (X)HTML for presentation.  XSLT  contains  quite
       many functions and learning them all may take some effort. This document assumes a basic level of understanding of XSLT.

       Since  XSLT  is based on a functional programming approach with pattern matching and recursion it is possible to write similar style sheets
       in Erlang. At least for basic transforms. This document describes how to use the XPath implementation together with Erlangs pattern  match-
       ing and a couple of functions to write XSLT like transforms.

       This approach is probably easier for an Erlanger but if you need to use real XSLT stylesheets in order to "comply to the standard" there is
       an adapter available to the Sablotron XSLT package which is written i C++. See also the Tutorial .

EXPORTS

       built_in_rules(Fun, E) -> List

	      The default fallback behaviour. Template funs should end with:
	      template(E) -> built_in_rules(fun template/1, E) .

       select(String::string(), E) -> E

	      Extracts the nodes from the xml tree according to XPath.

	      See also: value_of/1 .

       value_of(E) -> List

	      Types  E = unknown()

	      Concatenates all text nodes within the tree.

	      Example:

		<xsl:template match="title">
		  <div align="center">
		    <h1><xsl:value-of select="." /></h1>
		  </div>
		</xsl:template>

	      becomes:

		 template(E = #xmlElement{name='title'}) ->
		   ["<div align="center"><h1>",
		     value_of(select(".", E)), "</h1></div>"]

       xslapply(Fun::Function, EList::list()) -> List

	      Types  Function = () -> list()

	      xslapply is a wrapper to make things look similar to xsl:apply-templates.

	      Example, original XSLT:

		<xsl:template match="doc/title">
		  <h1>
		    <xsl:apply-templates/>
		  </h1>
		</xsl:template>

	      becomes in Erlang:

		template(E = #xmlElement{ parents=[{'doc',_}|_], name='title'}) ->
		  ["<h1>",
		   xslapply(fun template/1, E),
		   "</h1>"];

AUTHORS

       <>

								    xmerl 1.2.8 						    xmerl_xs(3erl)