page_util_norm_peg(n) [mojave man page]
page_util_norm_peg(n) Parser generator tools page_util_norm_peg(n) __________________________________________________________________________________________________________________________________________________ NAME
page_util_norm_peg - page AST normalization, PEG SYNOPSIS
package require page::util::norm_peg ?0.1? package require snit ::page::util::norm::peg tree _________________________________________________________________ DESCRIPTION
This package provides a single utility command which takes an AST for a parsing expression grammar and normalizes it in various ways. The result is called a Normalized PE Grammar Tree. Note that this package can only be used from within a plugin managed by the package page::pluginmgr. API
::page::util::norm::peg tree This command assumes the tree object contains for a parsing expression grammar. It normalizes this tree in place. The result is called a Normalized PE Grammar Tree. The following operations are performd [1] The data for all terminals is stored in their grandparental nodes. The terminal nodes and their parents are removed. Type information is dropped. [2] All nodes which have exactly one child are irrelevant and are removed, with the exception of the root node. The immediate child of the root is irrelevant as well, and removed as well. [3] The name of the grammar is moved from the tree node it is stored in to an attribute of the root node, and the tree node removed. The node keeping the start expression separate is removed as irrelevant and the root node of the start expression tagged with a marker attribute, and its handle saved in an attribute of the root node for quick access. [4] Nonterminal hint information is moved from nodes into attributes, and the now irrelevant nodes are deleted. Note: This transformation is dependent on the removal of all nodes with exactly one child, as it removes the all 'Attribute' nodes already. Otherwise this transformation would have to put the information into the grandparental node. The default mode given to the nonterminals is value. Like with the global metadata definition specific information is moved out out of nodes into attributes, the now irrelevant nodes are deleted, and the root nodes of all definitions are tagged with marker attributes. This provides us with a mapping from nonterminal names to their defining nodes as well, which is saved in an attribute of the root node for quick reference. At last the range in the input covered by a definition is computed. The left extent comes from the terminal for the nontermi- nal symbol it defines. The right extent comes from the rightmost child under the definition. While this not an expression tree yet the location data is sound already. [5] The remaining nodes under all definitions are transformed into proper expression trees. First character ranges, followed by unary operations, characters, and nonterminals. At last the tree is flattened by the removal of superfluous inner nodes. The order matters, to shed as much nodes as possible early, and to avoid unnecessary work later. 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, graph walking, normalization, page, parser generator, text processing, tree walking CATEGORY
Page Parser Generator COPYRIGHT
Copyright (c) 2007 Andreas Kupries <andreas_kupries@users.sourceforge.net> page 1.0 page_util_norm_peg(n)
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page_util_peg(3tcl) Parser generator tools page_util_peg(3tcl) __________________________________________________________________________________________________________________________________________________ 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 _________________________________________________________________ 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 nonter- minal 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. 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 processing, transformation CATEGORY
Page Parser Generator COPYRIGHT
Copyright (c) 2007 Andreas Kupries <andreas_kupries@users.sourceforge.net> page 1.0 page_util_peg(3tcl)