Vim9: line continuation and comments

[Bram Moolenaar]

In case you haven't been keeping track of progress of the Vim9 script
features, here are two items I would like to highlight.

So far line continuation was indicated by a backslash in the next line.
This was done so that no old Vi command would break. It leads to ugly
code in some places, such as defining a list constant:

let mylist = [
\ 'one',
\ 'two',
\ 'three',
\]

Since in Vim9 script we do not need to be 100% backwards compatible, I
made line continuation work where it could be recognized. That is, if
we run into the end of a line but the command isn't finished yet, we
assume it continues in the next line. This works for a list constant
where we haven't seen the ] yet:

let mylist = [
'one',
'two',
'three',
]

This also works for expressions, so long as it ends in an operator, so
that Vim knows another expression must be following:

let text = header ..
GetMiddle() ..
tail

Inside an expression a comment starting with a double quote is hard to
distinguish from a string constant. Thus in the above example there
cannot be a comment after the ".." operator.

To make it possible to add a comment here we need a different prefix.
Many languages use "#" and that works here as well:

let text = header .. # header comes first
GetMiddle() .. # body
tail # finish

The # character was not used in legacy Vim script, because ":#" is a
valid command. But we don't really need it, ":number" does the same.

One restriction: #{ starts a dictionary, thus that can't be used to
start a comment. We can live with that.

Together this works nicely to comment function arguments:

def MySplitter(
text: string, # what to split
pat: string, # separator pattern
max = -1, # maximum nr of splits
): list<string>

Enjoy!

This is not completely implemented yet, work in progress...

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/// Bram Moolenaar -- Br...@Moolenaar.net -- http://www.Moolenaar.net \\\
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[Christian Brabandt]

On Mo, 13 Apr 2020, Bram Moolenaar wrote:

> This is not completely implemented yet, work in progress...

Thanks, for the feedback. Looks very promising!

Best,
Christian
--
Das Chaos will anerkannt, will gelebt sein, ehe es sich in eine neue
Ordnung bringen läßt.
-- Hermann Hesse