page_util_flow(n) [suse man page]
page_util_flow(n) Parser generator tools page_util_flow(n) __________________________________________________________________________________________________________________________________________________ NAME
page_util_flow - page dataflow/treewalker utility SYNOPSIS
package require page::util::flow ?0.1? package require snit ::page::util::flow start flowvar nodevar script flow visit node flow visitl nodelist flow visita node... _________________________________________________________________ DESCRIPTION
This package provides a single utility command for easy dataflow based manipulation of arbitrary data structures, especially abstract syn- tax trees. API
::page::util::flow start flowvar nodevar script This command contains the core logic to drive the walking of an arbitrary data structure which can partitioned into separate parts. Examples of such structures are trees and graphs. The command makes no assumptions at all about the API of the structure to be walked, except that that its parts, here called nodes, are identified by strings. These strings are taken as is, from the arguments, and the body, and handed back to the body, without modification. Access to the actual data structure, and all decisions regarding which nodes to visit in what order are delegated to the body of the loop, i.e. the script. The body is invoked first for the nodes in the start-set specified via start), and from then on for the nodes the body has requested to be visited. The command stops when the set of nodes to visit becomes empty. Note that a node can be visited more than once. The body has complete control about this. The body is invoked in the context of the caller. The variable named by nodevar will be set to the current node, and the variable named by flowvar will be set to the command of the flow object through which the body can request the nodes to visit next. The API provided by this object is described in the next section, FLOW API. Note that the command makes no promises regarding the order in which nodes are visited, excpt that the nodes requested to be visited by the current iteration will be visited afterward, in some order. FLOW API
This section describes the API provided by the flow object made accessible to the body script of ::page::util::flow. flow visit node Invoking this method requests that the node n is visited after the current iteration. flow visitl nodelist Invoking this method requests that all the nodes found in the list nodelist are visited after the current iteration. flow visita node... This is the variadic arguments form of the method visitl, see above. 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
dataflow, graph walking, page, parser generator, text processing, tree walking COPYRIGHT
Copyright (c) 2007 Andreas Kupries <andreas_kupries@users.sourceforge.net> page 1.0 page_util_flow(n)
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page_util_norm_peg(3tcl) Parser generator tools page_util_norm_peg(3tcl) __________________________________________________________________________________________________________________________________________________ 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(3tcl)