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xor stuff

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mes5k 2004-02-04 04:00:31 +00:00
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@ -347,6 +347,62 @@ floats, etc.) then just declare the <b>UnlabeledMultiArg</b> as type
<i>string</i>
and parse the different values yourself.
<a name="XOR"></a>
<h3>I want one argument or the other, but not both...</h3>
<b>New Feature!</b> Suppose you have a command that must read input from one
of two possible locations, either a local file or a URL. The command
<i>must</i> read something, so <i>one</i> argument is required, but not both,
yet neither argument is strictly necessary by itself. This is called
"exclusive or" or "XOR". To accomodate this situation, there is now an
option to add two or more <b>Arg</b>s to a <b>CmdLine</b> that are exclusively
or'd with one another: xorAdd(). This means that at exactly one of
the <b>Arg</b>s must be set and no more.
<br> <br>
xorAdd() comes in two flavors, either xorAdd(Arg& a, Arg& b) to add just
two <b>Arg</b>s to be xor'd and xorAdd( vector<Arg*> xorList ) to add more
than two <b>Arg</b>s.
<br> <br>
<pre>
...
ValueArg < string > fileArg("f","file","File name to read",true,"homer",
"filename");
ValueArg < string > urlArg("u","url","URL to load",true,
"http://example.com", "URL");
cmd.xorAdd( fileArg, urlArg );
cmd.parse(argc, argv);
...
</pre>
<br> <br>
Once one <b>Arg</b> in the xor list is matched on the <b>CmdLine</b> then
the others in the xor list will be marked as set. The question then, is how to
determine which of the <b>Arg</b>s has been set? This is accomplished by
calling the isSet() method for each <b>Arg</b>. If the <b>Arg</b> has been
matched on the command line, the isSet() will return <b>TRUE</b>, whereas
if the <b>Arg</b> has been set as a result of matching the other <b>Arg</b>
that was xor'd isSet() will return <b>FALSE</b>. (Of course, if the <b>Arg</b>
was not xor'd and wasn't matched, it will also return <b>FALSE</b>.)
<br> <br>
<pre>
...
if ( fileArg.isSet() )
readFile( fileArg.getValue() );
else if ( urlArg.isSet() )
readURL( urlArg.getValue() );
else
// Should never get here because TCLAP will note that one of the
// required args above has not been set.
throw("Very bad things...");
...
</pre>
<br> <br>
<a name="VISITORS"></a>
<h2>Visitors</h2>
Disclaimer: Almost no one will have any use for Visitors, they were added