programming: doifdefined & friends

programming: doifdefined & friends

[Henning Hraban Ramm]

While I can't cope with counters, I'm trying other stuff that I don't  
understand:
How must I use \doifdefined & friends?

Consider this snippet:

-----
\starttext

\def\myvar{JAJAJA}

\input tufte
\doifdefined{\myvar}{\par bla \myvar blub\par}
\input tufte

\stoptext
-----

I'd guess it would print "bla JAJAJAblub" between the two Tufte texts  
and don't if I comment \def\myvar.

But I guess wrongly: It does nothing in this case, and complains  
about undefined \myvar in the latter.

But if I really want to check if something is defined before I try to  
use it, how must I write it?
(Expansion magic?)


Greetlings from Lake Constance!
Hraban
---
http://www.fiee.net/texnique/
http://contextgarden.net
http://www.cacert.org (I'm an assurer)

Re: programming: doifdefined & friends

[Henning Hraban Ramm]

Am 2006-10-05 um 02:42 schrieb Henning Hraban Ramm:

> -----
> \starttext
>
> \def\myvar{JAJAJA}
>
> \input tufte
> \doifdefined{\myvar}{\par bla \myvar blub\par}
> \input tufte
>
> \stoptext
> -----

Sorry for bothering you, I found it myself: I must leave out the  
backslash in the condition.

But so I'm still stuck with this snippet from the LilyPond module,  
where Christopher used a lot of catcode trickery:

-----
/doifdefined{lily!fontname}/bgroup
\layout {/string^^J
	\override Staff.TimeSignature  #'font-name = #/lily!fontname/string^^J
	\override Staff.MultiMeasureRestText  #'font-name = #/lily!fontname/ 
string^^J
	\override Score.LyricText  #'font-name = #/lily!fontname/string^^J
	\override ChordNames.ChordName  #'font-name = #/lily!fontname/string^^J
}/string^^J
/egroup
-----
gives:
! Undefined control sequence.
\lily!prefix ...ure #'font-name = #\lily!fontname
                                                   \string
\override Staff....
<argument> ...nd-\the \lily!figures ]\lily!prefix
                                                   \lily!hash (set- 
global-sta...

\expanded ...\long \xdef \@@expanded {\noexpand #1
                                                   }\@@expanded
\dodostartlilypond ...e \lily!fragmentsuffix \fi }
                                                   \endbuffer \par  
\def \LP {...
l.43 \stoplilypond
-----

I'm trying to introduce a "fontname" setting in \setuplilypond that  
should generate the \layout{...} block in the LilyPond file if used  
and nothing if not.

I know how to do that with numbers and yes/no settings, because there  
are some samples in the module, but unfortunately no string settings  
- and I don't understand the samples that I found in the ConTeXt  
sources either.


Greetlings from Lake Constance!
Hraban
---
http://www.fiee.net/texnique/
http://contextgarden.net
http://www.cacert.org (I'm an assurer)

Re: programming: doifdefined & friends

[Henning Hraban Ramm]

Sorry, last one for tonight.
Just forget my question - it wouldn't work this way anyway.

- the \doif stuff got printed in the LilyPond file instead of executed
- my LilyPond font settings can't work at that place, because  
\overrides must stand in their appropriate score section

:-(


Greetlings from Lake Constance!
Hraban
---
http://www.fiee.net/texnique/
http://contextgarden.net
http://www.cacert.org (I'm an assurer)

Re: programming: doifdefined & friends

[Aditya Mahajan]

On Thu, 5 Oct 2006, Henning Hraban Ramm wrote:

> While I can't cope with counters, I'm trying other stuff that I don't
> understand:
> How must I use \doifdefined & friends?
>
> Consider this snippet:
>
> -----
> \starttext
>
> \def\myvar{JAJAJA}
>
> \input tufte
> \doifdefined{\myvar}{\par bla \myvar blub\par}
> \input tufte
>
> \stoptext
> -----
>
> I'd guess it would print "bla JAJAJAblub" between the two Tufte texts
> and don't if I comment \def\myvar.
>
> But I guess wrongly: It does nothing in this case, and complains
> about undefined \myvar in the latter.

That is because \doifdefined is for strings. It adds a \csname ... 
\endcsname around its first argument.

> But if I really want to check if something is defined before I try to
> use it, how must I write it?

The plain tex way

  \ifx\myvar\undefined
    %Nothing here
  \else
    \par bla \myvar blub\par
  \fi

or the context way (for strings)

  \doifdefined{myvar}{\par bla \myvar blub\par}


Aditya