Is this control sequence, or JP char, or non-JP char?

ifisjp.tex

\makeatletter
% https://tex.stackexchange.com/questions/21466/test-if-token-is-a-control-sequence
\def\@ifismacro#1{%
  \begingroup\escapechar=-1
    \edef\x{\endgroup\def\noexpand\first{\string#1}}\x
  \begingroup\escapechar=`\\
    \edef\x{\endgroup\def\noexpand\second{\string#1}}\x
  \ifnum\pdfstrcmp{\first}{\second}=\z@
    \expandafter\@secondoftwo % no backslash in front
  \else
    \expandafter\@firstoftwo  % backslash in front
  \fi}
% (u)pTeX-specific: is a character token is JP or non-JP?
\ifx\enablecjktoken\@undefined
\def\@ifisjp#1{% pTeX version
  \ifnum`#1<255\relax
    \expandafter\@secondoftwo
  \else
    \expandafter\@firstoftwo
  \fi}
\else
\def\@ifisjp#1{% upTeX version
  \ifnum\kcatcode`#1=15\relax
    \expandafter\@secondoftwo
  \else
    \expandafter\@firstoftwo
  \fi}
\fi
%
\def\report#1{\@ifismacro{#1}{\typeout{CS}}
  {\@ifisjp{#1}{\typeout{JP}}{\typeout{non-JP}}}}
\makeatother

\typeout{===== pTeX and upTeX common =====}
\report{A}% => non-JP
\report{漢}% => JP
\report{\relax}% => CS
\report{\"}% => CS
\let\pippo=a
\report{\pippo}% => CS

\ifx\enablecjktoken\undefined
\typeout{===== pTeX-specific behavior =====}
% pTeX: each character code range is given a fixed behavior
% of either JP or non-JP.
\report{°}% => JP (euc: "A1EB = 41451, sjis: "818B = 33163)
\report{^^b0}% => non-JP
\report{^^c0}% => non-JP
%
\else
\typeout{===== upTeX-specific behavior =====}
% upTeX: each character code range (except 0--127, which are always non-JP)
% can have both JP and non-JP behavior.
\report{°}% => JP (U+00B0)
\report{^^b0}% => JP ... Common class by Unicode script
\report{^^c0}% => non-JP ... Latin-1 class by Unicode script
\kcatcode"A0=15\relax % move Common class to non-JP
\report{^^b0}% => non-JP
%
\fi
\typeout{=====}

\stop

Related:

• https://ml.texjp.org/pipermail/issue/2019-January/000210.html
• https://ml.texjp.org/pipermail/issue/2019-January/000212.html

Note:

• The argument of example macro \report should be only one token.
• \catcode, \kcatcode and ` can be applied only to a character token. So, first test if the token is a control sequence or not.
• \catcode is not allowed for JP characters. So, we have to test if the character token is JP char or non-JP char. Here we should note the different behavior of \kcatcode between pTeX and upTeX (the latter one allows flexible changing of
  JP / non-JP classification).