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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::flatten treequery tree
::page::util::peg::peOf tree eroot
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.
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.
As ::page::util::peg::symbolNodeOf, but returns the symbol name instead of the node.
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.
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.
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.
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.
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.
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, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category page of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.
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Page Parser Generator
Copyright © 2007 Andreas Kupries