Re: How to use matcharg(2)[1] to set search register?

On 2012-07-08, Bee wrote:
> On Jul 8, 3:33 pm, Gary Johnson wrote:
> > On 2012-06-24, Bee wrote:
> > > On Jun 24, 10:32 am, Gary Johnson wrote:
> > > > On 2012-06-24, Bee wrote:
> > > > > 2match has been set and is working.
> >
> > > > > :echo matcharg(2)[1] returns the correct pattern.
> >
> > > > > Why does this not set the search register?
> >
> > > > > let @/=matcharg(2)[1]
> >
> > > > It works for me.
> >
> > > > Are you setting @/ within a function and expecting that setting to
> > > > persist after the function returns? That won't work because
> > > > functions use their own instances of @/.
> >
> > > > Regards,
> > > > Gary
> >
> > > Thank you, I now see from :help "/
> >
> > > 9. Last search pattern register    "/                 *quote_/* *quote/*
> > > ...
> > > "Note that the valued is restored when returning from a function"
> >
> > > --And--
> >
> > > *function-search-undo*
> > > The last used search pattern and the redo command "."
> > > will not be changed by the function.  This also
> > > implies that the effect of |:nohlsearch| is undone
> > > when the function returns.
> >
> > > BUT...
> >
> > > When the following function exits, the '/' register is still set as it
> > > was in the function and 'n' will find the next occurance.
> > > What should it have been restored to?
> >
> > > " toggle match end of long lines
> > > hi OverLength NONE cterm=underline ctermbg=darkyellow
> > > function! OverLength(n)
> > >   if matcharg(2)[0] == "OverLength"
> > >     2match none OverLength
> > >   else "!greater than nth virtual column :help \%>v
> > >     let @/='\%>' . a:n . 'v.*'
> > >     execute '2match OverLength /' . @/ . '/'
> > >   endif
> > > endf
> >
> > I would expect it to be restored to whatever value it had before the
> > OverLength() function was called.  Are you sure that the '/'
> > register was not already set to that pattern before the function
> > was called?
> >
> > If you can do this:
> >
> >     1.  :let @/= "hello"
> >     2.  :call OverLength(40)
> >     3.  :echo @/
> >
> > and see that the '/' no longer contains "hello", then you may have
> > found a bug in Vim.
> >
> > BTW, according to ":help 2match", clearing the match is done with
> > ":2match none"--the second argument is not needed and appears to be
> > ignored.
> >
> > Regards,
> > Gary
>
> To make it clearer:
>
> :let @/= "hello"
>
> :echo @/
> hello
>
> :call OverLength(40)
>
> :echo @/
> \%>40v.*
>
> Bill

I just tried that myself, as I suppose I could have earlier, and I
see the same thing. I even simplified the function to this:

function! MyTest()
let @/='world'
endfunction

and after calling MyTest(), the '/' register contains "world".

However, if I change the function to this:

function! MyTest()
/match
echo @/
endfunction

and call it, the cursor moves to the next occurrence of "match" in
the file and the string "match" is echoed to the command line, but
executing ':echo @/' displays "hello".

So it appears that setting the '/' register indirectly alters a
local copy, but setting it directly with :let also alters the global
copy. I think that's a bug.

The results were the same on versions 7.2.330 and 7.3.584, so it has
been like this for a while.

Regards,
Gary

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