Re: What is the point of \on-the-fly ?

[David Kastrup]

Paul <address@hidden> writes:

> On 06/12/2017 01:00 AM, David Kastrup wrote:
>
>> The use case is similar to that of lambda: creating a procedure on the
>> fly without giving it a name.
>
> Ah, got it.  Then makes sense to avoid having to use on-the-fly, by
> converting those named on-the-fly procedures into actual markup
> commands.
>
> Just thinking out loud, but if define-markup-command worked like
> define-music-function and friends (i.e. like lambda) so that they
> returned a procedure, like this:
>
>   command-name = #(define-markup-command (layout props args...) ...
>
>   (define command-name (define-markup-command (layout props args...) ...
>
> Rather than the current form:
>
>   (define-markup-command (command-name layout props args...) ...
>
> Would that remove the need for on-the-fly or am I missing something?
> I'm sure that would not be a trivial change -- again just thinking out
> loud.

(define-markup-command bla)

does not define bla, but rather bla-markup, make-bla-markup and bits and
pieces used for signatures and the markup macro.

Even then, creating music functions on the fly _and_ using them requires
use of $(define-music-function ...) since #(define-music-function ...)
does not call the generated music function (would be hard assigning a
music function if it got called right away...).

I actually just proposed an issue where you _can_ call markup functions
on the fly when defined properly.  But the process of assigning a markup
command with all that it entails cannot be done in the same manner.

Since we can generate markup commands "on the fly" with \markup
... \etc, assigning them in a manner corresponding to
define-markup-command might be nice.

I suggested

\markup bla = ...

for it without being all too clear about whether this implied \markup
mode, allowing for

\markup bla = \bold \large \etc

rather than

\markup bla = \markup \bold \large \etc

There were no real comments (and I am fuzzy on the details of the
ensuing non-discussion as far as I remember it) so this proposal petered
out.

-- 
David Kastrup