On 2012–12–23 Ben Fritz wrote: > From :help fold-expr: > > > Try to avoid the "=", "a" and "s" return values, since Vim often has to > > search > > backwards for a line for which the fold level is defined. This can be slow. > > The problem is that Vim calls your foldexpr once for every line, > but for each line using =, a, or s, it must call it recursively on > the previous line to get the foldlevel of that line, which calls > it recursively again to get the previous line for its own > foldlevel, etc. where the recursion only ends when a foldlevel is > defined explicitly (at the first line in the file).
That explains it, thanks.
> To avoid this you could store foldlevels of previous lines in a
> lookup table internally to your function, and look up the
> foldlevel from your variable if present, or using the foldlevel()
> function instead of returning =, a, and s items.
I read the manual entry about foldlevel() but I didn't really grasp
the idea (it's my first attempt at writing a fold expression). How
to use foldlevel() to create an efficient expression for a file like
the following?
start
alpha
start
beta
stop
stop
start
gamma
start
delta
stop
stop
Marco
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