+ Maybe 'const' can be followed by name of a const which forms the namespace.
+ So a struct bar containing x and y could be initialized
+ const foo::bar
+ x ::= 1; y::=2
+ Then an array could be extended with [+]
+ const ra[+]
+ x::=2 ...
+
+ The syntax needs to be clearly different from
+ const a::num=1; b::=2
+ if that is still allowed
+ Maybe the '=' is enough to differentiate
+
+- IN and OUT should not be completely ignored when not expected.
+ As well as causing NEWLINE to be ignored, there should be some
+ balance requirement. Some productions should be required to be
+ balanced. Lists should not have gratuitous indents.
+ Revisit everything I considered before, but now consider it only
+ for ignore IN/OUT.