allowed characters in identifiers

8.22: adda/lexicon/allowed characters in identifiers:
. if the allowed characters in an identifier
could include the dot,
then there could be confusion in places,
as to whether the dot was declaring a var:
eg, what if you have the name x.F.int,
and then -- forgetting you did that --
decided later to define F.type ?
. now x.F is ambiguous:
are you declaring x to be F.type?
or are you referring to x.F.int ?
. therefore, the allowed identifiers are
first character is a letter
or the character (_);
and, subsequent characters are alphanums
or the characters (') (_) (-);
anthing else gets put in a box:
eg, [x.F].int; .