2016-07-30 22:17 GMT+03:00 Bram Moolenaar <[email protected]>:
>
> Ken Takata wrote:
>
>> 2016/7/30 Sat 5:38:42 UTC+9 Bram Moolenaar wrote:
>> > Patch 7.4.2120
>> > Problem: User defined functions can't be a closure.
>> > Solution: Add the "closure" argument. Allow using :unlet on a bound
>> > variable. (Yasuhiro Matsumoto, Ken Takata)
>> > Files: runtime/doc/eval.txt, src/testdir/test_lambda.vim,
>> > src/userfunc.c,
>> > src/eval.c src/proto/userfunc.pro
>>
>> I had a report that this patch doesn't work as expected:
>>
>> function! Foo()
>> let x = 0
>> function! Bar() closure
>> let x += 1
>> return x
>> endfunction
>> return function('Bar')
>> endfunction
>>
>> let Count = Foo()
>> echo Count() " => 1
>> echo Count() " => 2
>> echo Count() " => 3
>>
>> let Count2 = Foo()
>> echo Count() " => 1 (Should be 4)
>
> Calling Foo() creates a new context in which "x" is set to zero.
> And a new Bar() is created that uses this "x". It should not re-use the
> existing Bar(), it is still in use, being referenced.
>
> Thus where it says: /* redefine existing function */
> It should leave that function alone and create a new one. But the new
> Bar() must be the one that's found in the global scope. Thus it's a mix
> of defining a new function and replacing an existing one.
The main problem is that “funcrefs” are not a funcrefs, they are
string keys that will be looked up in a hash with all functions.
extended-funcref was fixing this and a bit more: l̶a̶m̶b̶d̶a̶s̶
̶a̶n̶d̶ anonymous functions were no longer recorded in any global
hash, also allowed using Python callable objects as funcrefs. Do not
remember how I coped/planned to cope with using :function or something
else to print anonymous functions’ body, now I would simply suggest
`get(Fref, 'code')` which will return a list of strings or zero (e.g.
for Python functions), also `get(Fref, 'sid')`, `get(Fref, 'slnum')`
and `scriptpath(sid)` (last one has other use-cases, so `get(Fref,
'sid')`+`scriptpath(sid)` and not `get(Fref, 'sfile')`).
If interested, I can try and resurrect this patch in Neovim for
somebody else to port it to Vim. I am not planning to write such big
patches for Vim any more.
>
>> The function Bar() should have been handled like a lambda function which
>> means
>> reference counting is needed.
>> Using a dict function with closure works as expected:
>>
>> function! Foo()
>> let x = 0
>> let d = {}
>> function! d.Bar() closure
>> let x += 1
>> return x
>> endfunction
>> return d.Bar
>> endfunction
>>
>> (But this might be not so useful.)
>> I don't have a good idea to fix this problem. Current idea is:
>>
>> * "function! Bar() closure" creates an unnamed function with the internal
>> name
>> "<lambda>N", and
>> * The Funcref is assign to a local variable "Bar".
>>
>> Not sure this goes well...
>
> --
> Lawmakers made it obligatory for everybody to take at least one bath
> each week -- on Saturday night.
> [real standing law in Vermont, United States of America]
>
> /// Bram Moolenaar -- [email protected] -- http://www.Moolenaar.net \\\
> /// sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ \\\
> \\\ an exciting new programming language -- http://www.Zimbu.org ///
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>
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