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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 syntax
    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.



  

  
Invoking this method requests that the node n is visited after the
      current iteration.

  

  
Invoking this method requests that all the nodes found in the list
      nodelist are visited after the current iteration.

  

  
This is the variadic arguments form of the method visitl, see
      above.








BUGS, IDEAS, FEEDBACK


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
    [http://core.tcl.tk/tcllib/reportlist]. Please also report any ideas for
    enhancements you may have for either package and/or documentation.


When proposing code changes, please provide unified diffs,
    i.e the output of diff -u.


Note further that attachments are strongly preferred over
    inlined patches. Attachments can be made by going to the Edit form of
    the ticket immediately after its creation, and then using the left-most
    button in the secondary navigation bar.






KEYWORDS


dataflow, graph walking, page, parser generator, text processing,
    tree walking






CATEGORY


Page Parser Generator






COPYRIGHT


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








  

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