Methods common to all pattern objects
=====================================

Patterns are the basic vector workhorse variable of the lazyNut system,
being used for actual and hypothetical layer states, inputs and outputs, and
intermediate computations.

description
-----------

	some_pattern description

The description has the additional element `Summary` that contains a
human-readable(ish) summary of the current value of the pattern.

set
---

	some_pattern set rep values...

Set the representation of `some_pattern` to `rep`, its subtype to the
default for `rep` and its value according to the zero or more `values`
given, according to the rules for `rep`.

set_equal
---------

	some_pattern set_equal source_pattern

Set the representation, subtype and value of `some_pattern` to be the same
as `source_pattern`.

get_summary
-----------

	some_pattern get_summary

Emit the same summary as in the description.

clear
-----

	some_pattern clear

Clear the value of `some_pattern` to the conceptually zero value for its
current subtype.