


page_util_peg(n)      Parser generator tools     page_util_peg(n)


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NAME
       page_util_peg - page PEG transformation utilities

SYNOPSIS
       package require page::util::peg  ?0.1?

       package require snit

       ::page::util::peg::symbolNodeOf tree node

       ::page::util::peg::symbolOf tree node

       ::page::util::peg::updateUndefinedDueRemoval tree

       ::page::util::peg::flatten treequery tree

       ::page::util::peg::getWarnings tree

       ::page::util::peg::printWarnings msg

       ::page::util::peg::peOf tree eroot

       ::page::util::peg::printTclExpr pe

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DESCRIPTION
       This  package  provides a few common operations to PEG transformations.
       They assume a Normalized PE Grammar Tree  as  input,  see  the  package
       page::util::norm::peg,  possibly  augmented with attributes coming from
       transformations not in conflict with the base definition.


API
       ::page::util::peg::symbolNodeOf tree node
              Given an arbitrary expression node in the AST tree it determines
              the node (itself or an ancestor) containing the name of the non-
              terminal symbol the node belongs to, and  returns  its  id.  The
              result  is  either  the  root of the tree (for the start expres-
              sion), or a definition node.

       ::page::util::peg::symbolOf tree node
              As ::page::util::peg::symbolNodeOf, but returns the symbol  name
              instead of the node.

       ::page::util::peg::updateUndefinedDueRemoval tree
              The  removal  of nodes in the AST tree can cause symbols to lose
              one or more users.

                   A used by B and C,
                   B is reachable,
                   C is not,



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page_util_peg(n)      Parser generator tools     page_util_peg(n)


                   so A now loses the node in the expression for C calling it,
                   or rather, not calling it anymore.

              This command updates the cross-references and which nonterminals
              are now undefined.

       ::page::util::peg::flatten treequery tree
              This  commands  flattens nested sequence and choice operators in
              the AST tree, re-using the treeql object treequery  to  run  the
              query determining which nodes to cut.

       ::page::util::peg::getWarnings tree
              This  command  looks at the attributes of the AST tree for prob-
              lems with the grammar and issues warnings. They do  not  prevent
              us  from  writing the grammar, but still represent problems with
              it the user should be made aware of.

              The result of the command is a  dictionary  mapping  nonterminal
              names to their associated warnings.

       ::page::util::peg::printWarnings msg
              The  argument of the command is a dictionary mapping nonterminal
              names to their associated warnings, as generated by,  for  exam-
              ple, the command ::page::util::peg::getWarnings.

              The  warnings  contained  therein are formatted and then printed
              via the log command page_info. This means that this command  can
              be  used  only  from  within  a  plugin  managed  by the package
              page::pluginmgr.

       ::page::util::peg::peOf tree eroot
              This command converts the parsing  expression  starting  at  the
              node  eroot in the AST tree into a nested list. The exact syntax
              of this list specified by the package grammar::peg.

       ::page::util::peg::printTclExpr pe
              This command converts the parsing expression  contained  in  the
              nested  list pe into a Tcl string which can be placed into a Tcl
              script.  See the package grammar::peg for the  exact  syntax  of
              pe.


BUGS, IDEAS, FEEDBACK
       This  document,  will  undoubtedly  contain  bugs  and  other problems.
       Please report such in the category  page  of  the  Tcllib  SF  Trackers
       [http://sourceforge.net/tracker/?group_id=12883].   Please  also report
       any ideas for enhancements you may have.

KEYWORDS
       PEG, page, parser generator, parsing expression grammar, text  process-
       ing, transformation

CATEGORY
       Page Parser Generator



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page_util_peg(n)      Parser generator tools     page_util_peg(n)


COPYRIGHT
       Copyright (c) 2007 Andreas Kupries <andreas_kupries@users.sourceforge.net>























































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