------------------------------------------------------------------------
'''struct command'''

'''struct''' <sub command> ?<arg> ...?

   '''struct create''' <structure name> <list>:   Creates an instance of the named structure type initialising the contents of the structure to the contents of the list. e.g.

	% set a [struct create node {root {} {}}]
	<feather::structure 0x2004e278>

   '''struct define''' <structure name> <definition>:   Defines a new structure type or redefines an old structure type. The definition is simply a list of member names. e.g.

	% struct define node {
	     data
	     left
	     right
	} 

   '''struct contents''' <structure instance>:   Returns the contents of the structure as a list.

As a structure is also a container it is possible to use the generic container [Feather Container] commands with it. e.g.

	% struct define node {
	     data
	     left
	     right
	} 
	% set a [struct create node {root {} {}}]
	<feather::structure 0x2004e278>
	% getx $a data
	root
	% setx $a left [struct create node {child1 {} {}}]
	% struct contents $a
	root {<feather::structure 0x2004ef18>} {}
	% getx $a left data
	child1