[NTG-context] Check the character after a macro

Wolfgang Schuster schuster.wolfgang at gmail.com
Fri May 1 21:10:38 CEST 2015


> Am 01.05.2015 um 20:41 schrieb Sam Ḥilluc <shilluc at gmx.com>:
> 
> On 2015-05-01 19:38, Otared Kavian wrote:
>> Hi,
>> 
>> You have several commands in ConTeXt doing what you are seeking to do: please look at the examples below:
>> 
>> %%% begin do-if-inset.tex
>> \starttext
>> \type{\doifinset{A}{A,B,C}{should go}:} \doifinset{A}{A,B,C}{should go}
>> 
>> \type{\doifinset{D}{A,B,C}{should go}:}  \doifinset{D}{A,B,C}{should participate}
>> 
>> 
>> \type{\doifnotinset{}{A,B,C}{not in the set}:} \doifnotinset{}{A,B,C}{not in the set}
>> 
>> \type{\doifnotinset{D}{A,B,C}{not in the set}:} \doifnotinset{D}{A,B,C}{not in the set}
>> 
>> \doifinsetelse{D}{A,B,C}{it is in the set}{it is not in the set}
>> 
>> \define\test{B}
>> 
>> \type{\doifinsetelse{\test}{A,B,C}{\test\ is in the set}{\test\ is not in the set}}
>> 
>> \doifinsetelse{\test}{A,B,C}{\test\ is in the set}{\test\ is not in the set}
>> \stoptext
>> %%% end do-if-inset.tex
>> 
>> Best regards: OK
> 
> This works for testing if a given character is in a set, but how can I retrieve
> that character just after the defined macro.
> 
> To give an example, a macro that adds a dot if the next character is not a
> comma.
> 
>    \MyMacro{text1} text2     ->      text1. text2
>    \MyMacro{text1}, text2    ->      text1, text2


You can use the \doifelsenextchar command to check the character after your command.

\define[1]\MyMacro
  {\doifelsenextchar{,}
     {#1}
     {#1. }}

\starttext

\MyMacro{left} right

\MyMacro{left}, right

\stoptext


The limitation of this method is that you check only for one character at a time
and when want to check for more you have to use multiple \doifelsenextchar lines.

\doifelsenextchar{,}
  {...}
  {\doifelsenextchar{.}
     {...}
     {...}}

Wolfgang
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