Re: xml processing: if elseif else / switch case

[Hans Hagen via ntg-context <ntg-context@ntg.nl>]

On 12/9/2021 5:11 PM, Wolfgang Schuster via ntg-context wrote:
> Joey McCollum via ntg-context schrieb am 09.12.2021 um 15:08:
>> I believe \orelse might be what you want. It works with most \if... 
>> macros, and it avoids nesting of \doifelse constructs. Here's an 
>> example, which I use in conditionally removing preceding punctuation 
>> if any other keys are defined before a specific one in an assignment:
>>
>> ```
>>       % If any of the preceding keys was specified, then replace any 
>> preceding punctuation with a space
>>     % and typeset the number with its CSL abbreviation, followed by a 
>> comma
>>       \ifdefined\btxsbllocvol
>> \removeunwantedspaces\removepunctuation\btxspace
>> \orelse\ifdefined\btxsbllocno
>> \removeunwantedspaces\removepunctuation\btxspace
>>       \fi
>> \orelse\ifdefined\btxsbllocpt
>>       [...]
>>       \fi
>> ```
> 
> The \fi at the end of each \orelse branch is wrong.
> 
> \ifdefined\btxsbllocvol
>      ...
> \orelse\ifdefined\btxsbllocno
>      ...
> \else
>      ...
> \fi
and when 'string' comparison is needed one can do:

\starttext

\def\foo{foo}
\def\ofo{ofo}
\def\oof{oof}

\def\XXX{ofo}

\ifcstok\XXX\foo
     FOO
\orelse\ifcstok\XXX\ofo
     OFO
\orelse\ifcstok\XXX\oof
     OOF
\else
     XXX
\fi

\def\XXX{\ofo}

\iftok{\XXX}{\foo}%
     FOO
\orelse\iftok{\XXX}{\ofo}%
     OFO
\orelse\iftok{\XXX}{\oof}%
     OOF
\else
     XXX
\fi

\ifcstok{\XXX}\foo
     FOO
\orelse\ifcstok{\XXX}\ofo
     OFO
\orelse\ifcstok\XXX}\oof
     OOF
\else
     XXX
\fi

\stoptext

watch the subtle differences. It all makes coding in tex primitives a 
bit more visual appealing and readable. Oone of the objectives of lmtx 
is that users can read the context code without pondering too much about 
the syntax or getting depressed by possibly obscure helper macros and 
expansion trickery.

Hans


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                                           Hans Hagen | PRAGMA ADE
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