Re: Updating alists (was: Tenuto marking too close to note)

[Jean Abou Samra]

Le 30/12/2021 à 23:04, Lukas-Fabian Moser a écrit :
> Hi Jean,
>
> > Both of these cases seem to work the same as in
> > current versions if I do
> >
> > [...]
> >
> >  SCM
> >  assq_tail (SCM key, SCM alist, SCM based_on = SCM_EOL)
> >  {
> > -  for (SCM p = alist; !scm_is_eq (p, based_on); p = scm_cdr (p))
> > +  for (SCM p = alist; scm_is_pair (p) && scm_is_pair (scm_car (p)) 
> > && !scm_is_eq (p, based_on); p = scm_cdr (p))
> >      {
> >        if (scm_is_eq (scm_caar (p), key))
> >          return p;
>
> Thanks! This seems to be a sensible precaution anyway, as it only 
> changes a certain crash into returning #f. So it might be sensible to 
> make this change anyway?


Turns out that you can already trigger the
crash in current versions with

\version "2.23.5"

x = 0
x.y.z = 1


So, yes, it might be sensible.


> > But I really don't have deep enough an insight on this code
> > to judge, sorry.
>
> I'm a bit surprised about the remark in the code stating that the 
> choice not to coalesce multiple override's was made to save the cost 
> of detecting them, as it does not seem to be a code path used heavily 
> at all.


As someone with usually bad intuition about
performance, I would just benchmark the
change.

Best,
Jean