I wrote:
> Patch 8.2.2204
> Problem: Vim9: using -> both for method and lambda is confusing.
> Solution: Use => for lambda in :def function.
> Files: runtime/doc/vim9.txt, src/vim9compile.c, src/userfunc.c,
> src/testdir/test_vim9_expr.vim
I thought I would give this a go and see how it works out.
The main advantage is that -> is only used for a method call, there is
no confusion with a lambda inside a dictionary literal. And it mostly
looks like how Javascript does this:
mapnew(list, (i, v) => i .. ": " .. v)
One problem I found is that supporting a statement block in {} is
interfering with a lambda that has only an expression and it is a
dictionary:
var Lambda = (a) => {key: a}
var Lambda = (a) => { command }
I think we can separate the two by requiring white space after the { for
a statement block, and requiring the key to be following the {
immediately for a dictionary. That feels natural.
In case putting the key right after the { is a problem, it's always
possible to use a return statement:
var Lambda = (a) => {
return { key: a }
}
Another thing is defining a lambda and calling it right away.
Previously the surrounding {} made it clear where the expression ends:
list->{a -> a + b}()
Now it becomes ambiguous:
list->(a) => a + b()
I think we can solve this by requiring putting the lambda in
parenthesis:
list->((a) => a + b)()
This then also supports another form of getting a function reference:
list->(Refs[1])()
This wasn't implemented yet.
Unless there are other doubts, I'll continue implementing lambda with =>
also at the script level, and later with the statement block.
And later remove the support for lambda with -> in Vim9 script.
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/// Bram Moolenaar -- [email protected] -- http://www.Moolenaar.net \\\
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