I'll admit that they get treated differently during translation
but I don't see why that is relevant.
(And they certainly don't fall into the
other three categories.) I feel a little bit uneasy referring
to \ NEWLINE as "white space".
N869
7.4.1.9 The isspace function
Description
[#2] The
standard white-space characters are the following: space
(' '), form feed ('\f'), new-line ('\n'), carriage return
('\r'), horizontal tab ('\t'), and vertical tab ('\v')
It's clear that \ NEWLINE sequences are not intended as white-space
in the language of the stanard document.
Here's the language of the standard document:
N869
5.1.1.2 Translation phases
3.
Whether each nonempty
sequence of white-space characters other than new-line
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
is retained or replaced by one space character is
implementation-defined.
It sure looks likes the language of the standard considers
newline, to be one of the white-space characters.
It almost seems as though you're trying to say
that a white-space character that gets treated differently
from the other white-space characters during translation,
shouldn't be considered a white-space character.