Hi Bram,
2016/9/22 Thu 2:37:29 UTC+9 Bram Moolenaar wrote:
> Christian Brabandt wrote:
>
> > Am 2016-09-21 00:00, schrieb Ken Takata:
> > > Hi Christian,
> > >
> > > 2016/9/21 Wed 5:31:26 UTC+9 Christian Brabandt wrote:
> > >> Hi,
> > >> I think I found a bug with lambda expressions.
> > >>
> > >> I was looking into writing some automated tests and was trying to use
> > >> the new lambda expressions. However this does not work as expected:
> > >>
> > >> Here is an example:
> > >> #v+
> > >> let a = ['FOOBAR "word"', 'FOOBAR "word2"']
> > >> let pat='^FOOBAR\s\+\zs"[^"]\+"'
> > >> let pat2='^FOOBAR\s\+\("[^"]\+"\)'
> > >> :echo map(copy(a), 'matchstr(v:val, g:pat)')
> > >> -> result ['"word"', '"word2"']
> > >> :echo map(copy(a), {val -> matchstr(val, g:pat)})
> > >> -> BUG: result ['""', '""'], expected ['"word"', '"word2"']
> > >> :echo map(copy(a), 'substitute(v:val, g:pat2,
> > >> ''\=submatch(1)'',"")')
> > >> -> result ['"word"', '"word2"']
> > >> :echo map(copy(a), {val -> substitute(val, g:pat2, '\=submatch(1)',
> > >> '')})
> > >> -> BUG: result ['0', '1'], expected ['"word", '"word2"']
> > >> #v-
> > >
> > > This is not a bug. map() always passes two arguments (key and val) to
> > > the
> > > specified Funcref. So,
> > >
> > >> :echo map(copy(a), {val -> matchstr(val, g:pat)})
> > >
> > > this should be:
> > >
> > > :echo map(copy(a), {key, val -> matchstr(val, g:pat)})
> > >
> > > Or you can still use v:val:
> > >
> > > :echo map(copy(a), {-> matchstr(v:val, g:pat)})
> >
> > Hm, should there be an error when only one argument is given?
> > Or at least it should be more stressed in the documentatio, that two
> > arguments are expected.
>
> How about extending the example in the help:
>
> If {expr2} is a |Funcref| it is called with two arguments:
> 1. The key or the index of the current item.
> 2. the value of the current item.
> The function must return the new value of the item. Example
> that changes each value by "key-value": >
> func KeyValue(key, val)
> return a:key . '-' . a:val
> endfunc
> call map(myDict, function('KeyValue'))
> < It is shorter when using a |lambda|: >
> call map(myDict, {key, val -> key . '-' . val})
> < If you do not use "val" you can leave it out: >
> call map(myDict, {key -> 'item: ' . key})
A similar update might be needed for `:help filter()`.
Regards,
Ken Takata
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