page_util_flow -
page dataflow/treewalker utility
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...
This package provides a single utility command for easy dataflow based
manipulation of arbitrary data structures, especially abstract syntax
trees.
-
::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.
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.
This document, will undoubtedly contain bugs and other problems.
Please report such in the category
page of the
http://sourceforge.net/tracker/?group_id=12883.
Please also report any ideas for enhancements you may have.
page, dataflow, tree walking, graph walking, parser generator, text processing