@currentlabel

The second parameter of \anc:lbl is a counter name, when such is know.

The ‘\@currentlabel’ comes sometimes with font info. Normally, it comes from \refstepcounter in the form of \the..counter-name... In such cases, we can take the counter name which is provided in the parameter of \cur:lbl.

<..cross ref..>+
 \NewConfigure{@:currentlabel}[1]{\concat:config\a:@:currentlabel{#1}}
 \let\a:@:currentlabel=\relax
 \def\cur:lbl#1{{\a:@:currentlabel
   <.body of cur:lbl.>\expandafter}\:currentlabel}
 -_-_-

<..body of cur:lbl..>
 \def\:currentlabel{\par}%
 \ifx\@currentlabel\:currentlabel
    \def\:currentlabel{\let\:currentlabel=\empty}%
 \else \def\:currentlabel{#1}%
    \edef\:currentlabel{\def\noexpand
                  \:currentlabel{\ifx\:currentlabel\empty
          \ifx \:@currentlabel\:UnDef \@currentlabel
          \else \:@currentlabel \fi
       \else
           \expandafter\ifx\csname #1:Count\endcsname\relax
              \expandafter\the\csname c@#1\endcsname
           \else \csname #1:Count\endcsname\fi
       \fi}}%
 \fi
 -_-_-

The \label command of latex invokes \cur:lbl{}. If \:@currentlabel is deined, it is the to be used for the current label. The \ltx@label command of amsmath.sty ignores it.

Whenever \@currentlabel is redefined, we also want to redefine \:@currentlabel. It is redefined in

• latex.ltx within \refstepcounter, \eqnarray, \@mpfootnotetext, and \@footnotetext;
• amsart.cls, amsbook.cls, and amsproc.cls within eqnarray and \@footnotetext;
• amsmath.sty within \df@tag and \make@df@tag@@;
• amstex.sty within \@currentlabel, \@seteqlabel, and multline*.

<..def :currentlabel for make@df@tag..>
 \let\cnt:currentlabel=\@currentlabel
 \def\:@currentlabel{\ifx \cnt:currentlabel\@currentlabel
    \expandafter\the\csname c@equation\endcsname\else \@currentlabel\fi}%
 -_-_-

<..def :currentlabel for refstepcounter..>
 \let\cnt:currentlabel=\@currentlabel
 \def\:@currentlabel{\ifx \cnt:currentlabel\@currentlabel
    \expandafter\the\csname c@#1\endcsname\else \@currentlabel\fi}%
 -_-_-

<..def :currentlabel for eqnarray..>
 \html:addr \edef\cur:th{<.haddr prefix.>\last:haddr r}%
 -_-_-

<..def :currentlabel for eqncr..>
 \anc:lbl r{}%
 -_-_-

<..def :currentlabel for pic-eqnarray..>
 <.def :currentlabel for eqnarray.>
 \def\cnt:currentlabel{\p@equation\theequation}%
 \def\:@currentlabel{\ifx \cnt:currentlabel\@currentlabel
    \expandafter\the\csname c@equation\endcsname\else \@currentlabel\fi}%
 -_-_-