page_util_peg(n) Parser generator tools page_util_peg(n) 







page_util_peg - page PEG transformation utilities








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












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.









  
::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
      nonterminal symbol the node belongs to, and returns its id. The result is
      either the root of the tree (for the start expression), 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,
	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 problems
      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 example, 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.










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.








PEG, page, parser generator, parsing expression grammar, text
    processing, transformation








Page Parser Generator








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








  

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