[Rd] [WISH / PATCH] possibility to split string literals across multiple lines

Simon Urbanek
Wed, 14 Jun 2017 13:48:22 -0000

As I recall this has been discussed at least a few times (unfortunately I'm
traveling so can't check the references), but the justification was never
satisfactory.

Personally, I wouldn't mind string continuation supported since it makes for
more readable code (I had one of my packages raise a NOTE in examples because
there is no way in R to split a long hash into multiple lines), but I would be
strongly against random removal of whitespaces as it's counter-intuitive,
misleading and makes it impossible to continue spaces on the next line. None of
the languages that I can think of with multiline strings do that as that's
way too dangerous.

Cheers,
Simon


> On Jun 14, 2017, at 6:58 AM, Andreas Kersting <r-devel at
akersting.de> wrote:
>
> Hi,
>
> I would really like to have a way to split long string literals across
multiple lines in R.
>
> Currently, if a string literal spans multiple lines, there is no way to
inhibit the introduction of newline characters:
>
> > "aaa
> + bbb"
> [1] "aaa\nbbb"
>
>
> If a line ends with a backslash, it is just ignored:
>
> > "aaa\
> + bbb"
> [1] "aaa\nbbb"
>
>
> We could use this fact to implement string splitting in a fairly
backward-compatible way, since currently such trailing backslashes should hardly
be used as they do not have any effect. The attached patch makes the parser
ignore a newline character directly following a backslash:
>
> > "aaa\
> + bbb"
> [1] "aaabbb"
>
>
> I personally would also prefer if leading blanks (spaces and tabs) in the
second line are ignored to allow for proper indentation:
>
> >   "aaa \
> +    bbb"
> [1] "aaa bbb"
>
> >   "aaa\
> +    \ bbb"
> [1] "aaa bbb"
>
> This is also implemented by this patch.
>
>
> An alternative approach could be to have something like
>
> ("aaa "
> "bbb")
>
> or
>
> ("aaa ",
> "bbb")
>
> be interpreted as "aaa bbb".
>
> I don't know the ins and outs of the parser of R (hence: please very
carefully review the attached patch), but I guess this would be more work to
implement!?
>
>
> What do you think? Is there anybody else who is missing this feature in the
first place?
>
> Regards,
> Andreas
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