CLOSURE v1.50 - compute transitive closure
Documentation revised 21 Oct 00 - Copyright (c) 1996-2000 by Rune Berg. TextTools Freeware.

Contents:


Usage Top || Next

closure [log logfile] [option] key [graphfile] [to resultfile]

See Understanding The Usage Section for details.


Description Top || Previous || Next

closure builds a directed graph of strings from the contents of graphfile, computes the set of strings belonging to the transitive closure starting at key, and writes that set to resultfile.

key is a string.

graphfile is an ASCII text file containing lines with (by default, but see -i option) whitespace-separated fields; this is described in more detail in the documentation for tcols. Each such field is considered a 'string' in this discussion.

For each line with strings S1 S2 ... SN in graphfile, closure adds nodes S1 S2 ... SN, and edges S1->S2 ... S1->SN, to the directed graph.

For each line with just one string S1 in graphfile, closure adds a node S1 (but no edges) to the directed graph.

closure ignores empty (whitespace only) lines in graphfile.

closure ensures the directed graph never contains duplicate nodes or edges.

If key is a string equal one of the strings in graphfile, then closure writes, to resultfile, one string per line: key and all strings reachable by following paths of edges from key's node.

If key does not appear in graphfile, then closure writes nothing to resultfile.

closure does not write duplicate strings.

If key is not equal to any of the strings in graphfile, resultfile will be empty.

If you don't specify graphfile, closure reads from standard input.
If you don't specify resultfile, closure writes to standard output.
If you don't specify logfile, closure writes error messages to standard error.


Example Top || Previous || Next

As an example, consider the (zoologically rather dubious) graphfile "fauna.txt":

      animal dog horse bird fish
      horse pony
      bird   sparrow eagle penguin
      fish whale shark
      shark  hammerhead great-white

For the command:

      closure fish fauna.txt

closure builds (internally) the graph:

      animal
        |--> dog
        |--> horse
        |      +--> pony
        |--> bird
        |      |--> sparrow
        |      |--> eagle
        |      +--> penguin
        +--> fish
               |--> whale
               |      |--> hammerhead
               |      +--> great-white
               +--> shark

and writes as result (though not necessarily in this order):

      fish
      whale
      shark
      hammerhead
      great-white


Options Top || Previous || Next

closure recognizes the following command line options:


Limitations Top || Previous || Next

See TextTools General Features for max. input line length and max. fields per line.

When using the -i option, make sure that graphfile does not have unwanted spaces at the end of lines - closure regards trailing spaces as part of the last field.

closure handles max. 5000 graph nodes.
closure handles max. 20000 graph edges.

Graph string data is limited only by available memory.


Return Codes Top || Previous || Next

closure returns with one of the following codes ("error levels"):

For more details, see TextTools General Features.


Version History Top || Previous

These are the released versions of closure:

End of document