Re: [groff] Changing A Defined String

[Tadziu Hoffmann]

> I created the ds FIND*COMMA from DATE*FULL and used .substring
> to find the pairing ``, ''.  I created the ds DATE*SHORT and
> subjected it to the successful .substring request.
> The only thing worth mentioning is that FIND*COMMA must be
> redefined at the beginning of each nested conditional, having
> been irrevocably altered during the previous conditional.

Would you mind posting your solution?  I'm curious as to how
you coded it.

Anyhow, in an earlier message I said I didn't think it was
possible to do all the required processing inside a single
string invocation.  It turns out I was wrong, it's entirely
possible.  Here is a sample solution, which strips off
everything up to the first comma, irrespective of context:


  .\" ----------------------------------------------------------------
  .de DATE*SHORT
  \c
  .ds AA \\*[DATE*FULL]
  .ds BB \\*[DATE*FULL]
  .YY
  .AA
  ..
  .de YY
  .ds CC \\*(BB
  .length BB \\*(BB
  .if \\n(BB>1 .substring BB 1
  .substring CC 0 0
  .if '\\*(CC',' .ZZ
  .if \\n(BB>1 .YY
  ..
  .de ZZ
  .if \\n(BB>1 .ds AA \\*(BB
  .if \\n(BB=1 .ds AA [single existing comma is last character]
  .nr BB 0
  ..
  .\" ----------------------------------------------------------------
  .ds DATE*FULL Friday, December 31, 2038
  .sp 3c
  Full date is: \*[DATE*FULL].
  .br
  Short date is: \*[DATE*SHORT].
  .\" ----------------------------------------------------------------


Of course, it's inefficient, because it has to repeat all
the processing every time you expand DATE*SHORT.


> > Or there's a `.while' IIRC.  :-)

The ".while" construct isn't strictly necessary,
because the roff language supports recursion.  8-)