Am Fr., 29. März 2019 um 02:23 Uhr schrieb Aaron Hill <lilyp...@hillvisions.com>: > > On 2019-03-28 3:14 pm, Thomas Morley wrote: > > Am Do., 28. März 2019 um 22:22 Uhr schrieb Aaron Hill > > <lilyp...@hillvisions.com>: > >> > >> On 2019-03-28 2:18 pm, Valentin Villenave wrote: > >> > On 3/28/19, Pedro Pessoa <pedrops...@gmail.com> wrote: > >> >> I imagined something like: > >> >> > >> >> %%% pseudo > >> >> #(define var > >> >> (not (is-bound? var) 0)) > >> >> %%% > >> > > >> > I’d probably probably do something like > >> > > >> > (null? (ly:parser-lookup 'var)) > >> > > >> > But I’m sure there are better ways :-) > >> > >> ;;;; > >> (if (not (defined? 'foo)) (define foo 47)) > >> ;;;; > >> > >> > >> -- Aaron Hill > > > > It's worth mentioning, the above will throw an error in guilev2: > > > > error: GUILE signaled an error for the expression beginning here > > # > > (if (not (defined? 'foo)) (define foo 47)) > > definition in expression context, where definitions are not allowed > > > > Probably better get used to below: > > > > #(if (not (defined? 'foo)) (ly:parser-define! 'foo 47)) > > Wouldn't... > > (define foo (if (defined? 'foo) foo 123)) > > ...work? Since foo is not defined (or redefined) until the S-expression > is fully evaluated, it should be able to resolve the existing value > should it exist. This also keeps the define at the top-level. > > -- Aaron Hill
Think so. Cheers, Harm _______________________________________________ lilypond-user mailing list lilypond-user@gnu.org https://lists.gnu.org/mailman/listinfo/lilypond-user
