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

Duncan Murdoch
Wed, 14 Jun 2017 11:12:09 -0000

On 14/06/2017 5:58 AM, Andreas Kersting wrote:
> Hi,
>
> I would really like to have a way to split long string literals across
> multiple lines in R.

I don't understand why you require the string to be a literal.  Why not
construct the long string in an expression like

  paste0("aaa",
         "bbb")

?  Surely the execution time of the paste0 call is negligible.

Duncan Murdoch

>
> 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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