itcl::is - test argument to see if it is a class or an object

       The  is  command  is used to check if the argument given is a class or an object; depending on the option
       given. If the argument if a class or object, then 1 is  returned.  Otherwise,  0  is  returned.   The  is
       command also recognizes the commands wrapped in the itcl code command.

       The  option  argument determines what action is carried out by the command.  The legal options (which may
       be abbreviated) are:

       isclasscommand
              Returns 1 if command is a class, and returns 0 otherwise.

              The fully qualified name of the class needs to be given as the command argument. So,  if  a  class
              resides in a namespace, then the namespace needs to be specified as well. So, if a class C resides
              in a namespace N, then the command should be called like:

                     isN::C
                         or
                     is::N::Cis object ?-classclassName? command
              Returns 1 if command is an object, and returns 0 otherwise.

              If  the  optional  "-class"  parameter  is  specified, then the command will be checked within the
              context of the class given. Note that className has to exist. If not, then an error will be given.
              So, if className is uncertain to be a class, then the programmer will need to check it's existance
              beforehand, or wrap it in a catch statement.

              So, if c is an object in the class C, in namespace N then these are the possibilities (all  return
              1):

                     set obj [N::C c]
                     itcl::is object N::c
                     itcl::is object c
                     itcl::is object $obj
                     itcl::is object [itcl::code c]

       class, object

itcl                                                   3.3                                             is(3itcl)

       itcl::is - test argument to see if it is a class or an object

itcl::isoption ?argarg...?
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