Purpose:  discuss the concept of command ''ensemble''

This concept has also been called "major/minor" commands by some
people (like myself) who didn't know the fancier name of ensemble.

Tcl has several kinds of commands.

The first, a simple command like '''[set]''', provides a very
simple interface.  One passes either one or two arguments.
Depending on the number of arguments, set either outputs the
value of the variable, or it sets the variable to a value.

A slightly more complex variation of this is a command that
takes arguments.  '''[puts]''' for instance has an optional
-nonewline flag as well as an optional output channel and an
output string.

Next in complexity comes the ensemble.  An example of this
command would be '''[string]'''.  What makes it more complex is
that string is an ''umbrella'' name for a variety of related
functionality.  String is the major ''command'' name, the minor
''subcommand'' names are things like ''bytelength'','''compare''', etc.

See TIP http://purl.org/tcl/tip/112.html for a TIP to include support
for developing this type of command in Tcl.

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[Category Tutorial]