[NTG-context] Re: Low-level macro help needed

[Wolfgang Schuster <wolfgang.schuster.lists@gmail.com>]

Rik Kabel schrieb am 16.10.2024 um 23:18:
> 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}}%
>        }


When you have argument after square brackets you have to use #: to 
continues scanning for arguments of the command. For the mandatory 
argument you should just use #2 and keep #= for the optional arguments 
which are only used when text enclosed in curly braces appears. The #* 
between the third and fourth argument allows spaces between them.

%%%% begin example
\tolerant\protected\def\Bi[#1]#:#2#*#=#*#=%
   {(1=#1)%
    (2=#2)%
    (3=#3)%
    (4=#4)}

\starttext

[\Bi[one]{two}{three}{four}]

[\Bi [one] {two} {three} {four}]

[\Bi [one] {two} {three}]

[\Bi [one] {two}]

[\Bi {two}]

[\Bi [one] {two}]

\stoptext
%%%% end example

To check whether a argument is empty or not you can use the \ifparameter 
command with the parameter to check (i.e. #1) as argument (don't forget 
the \or) but \doifempty etc. work as well.

%%%% begin example
\tolerant\protected\def\Bi[#1]#:#2#*#=#*#=%
   {\ifparameter#1\or
      First argument is used.
    \else
      First argument is missing or empty.
    \fi}

\starttext

\Bi {bar}

\Bi [] {bar}

\Bi [foo] {bar}

\stoptext
%%%% end example

Wolfgang
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