Hello Hans and developers,

I have been trying to convert some two- and three-step macros (as shown below) to single-step macros using the LMTX syntax given in the low-level macros manual. I have succeeded in many cases, but failed when the macro follows one particular group of patterns.

The group of patterns is similar to this macro to process

\MyMacro[optional]{Required}{Required}{Optional}

In this the number of arguments can be 2, 3, or 4.

A three-step solution might be as follows, which I use for a list of persons:

\defineregister[Bindex]
\setupregister [Bindex][n=1,
                        balance=no,
                        method=default, % or New follows Newton!
                        compress=no, % yes if not note number+q
                        expansion=yes,
                        pagecommand=\gobbleoneargument
                       ]

\starttexdefinition unexpanded Bi
  \dosingleempty\doBindex
\stoptexdefinition

\starttexdefinition unexpanded doBindex [#SORTAS]#INDEXED
  \def\SortAs{#SORTAS}%
  \def\Indexed{#INDEXED}%
  \dodoublegroupempty\doBindexFull
\stoptexdefinition

\starttexdefinition doBindexFull #BD#MORE
  \doifemptyelse{#MORE}
    {\Bindex[\SortAs]{\Indexed\ #BD}}
    {\Bindex[\SortAs]{\Indexed\ #BD\\ #MORE}}
\stoptexdefinition

with input like:

\Bi{Rumble, Walker}{1938|–|}%
\Bi{Runia, David Theunis}{1951|–|}{Classicist}%
\Bi{Rutherford, Ernest (Baron Rutherford of Nelson)}{1871|–|1937}{Physicist}%
\Bi{Saenger, Paul}{1945|–|}%
\Bi{Saldarini, Anthony J.}{1941|–|2001}%
\Bi{Salter, William M.}{1853|–|1931}%
\Bi[Saint-Exupery]{de Saint-Exupéry, Antoine}{1900|–|1944}%
\Bi{Santayana, George}{1863|–|1952}%
\Bi{Sapir, Edward}{1884|–|1939}{Linguist}%
\Bi[Schrodinger]{Schrödinger, Erwin}{1887|–|1961}{Physicist}%
\Bi[Spinoza]{de Spinoza, Baruch (Benedict de Spinoza, Bento de Espinosa)}{1632|–|1677}%

The best I can get with the newer syntax is a two-step:

\starttexdefinition unexpanded Bi
  \dosingleempty\doBindex
\stoptexdefinition
\tolerant\def\doBindex [#1]#=#=#=%
  {\doifemptyelse{#4}
    {\Bindex[#1]{#2\ #3}}%
    {\Bindex[#1]{#2\ #3\\ #4}}%
  }

In the low-level macros manual, near the end of chapter 2, it says that some day there may be a use for #?, #!, #<, or #>. If I am not missing something in the manual about how to provide that first optional argument as an empty value, I think I have one. Could [#?] always return a value (perhaps empty)? That would allow something like:

\tolerant\def\doBindex [#?]#=#=#=%
  {\doifemptyelse{#4}
    {\Bindex[#1]{#2\ #3}}%
    {\Bindex[#1]{#2\ #3\\ #4}}%
  }

--
Rik