JDK-8227870 - Escape Sequences For Line Continuation and White Space (Preview)
Brian Goetz
brian.goetz at oracle.com
Tue Oct 1 01:37:01 UTC 2019
This seems to cross the line between “new escape sequence” and “bespoke string literal language..."
> On Sep 30, 2019, at 9:30 PM, John Rose <john.r.rose at oracle.com> wrote:
>
> On Sep 30, 2019, at 4:45 AM, Jim Laskey <james.laskey at oracle.com> wrote:
>>
>> During the discussion on Text Blocks, several of you stated a need for a line continuation construct. I have since created a CSR to propose the creation of two new escape sequences: \<line terminator> and \s.
>>
>> https://bugs.openjdk.java.net/browse/JDK-8227870
>>
>
> One observation: Some traditional uses of \LT, as in C macros, makefiles, and shell,
> line up the \ characters in a single column as a sort of right-hand fence:
>
> foo bar \
> baz \
> bat
>
> This can be done only in settings where the spaces before the \ are treated as
> ancillary format, not payload characters. We could make a similar rule for multi-line
> literals, by saying that unescaped spaces *before* the \LT are also deleted when
> the \LT sequence is deleted.
>
> In other words, the \ at the end of the line is *not* a fence that transforms the
>
> So:
>
> var x = “””
> foo bar \
> baz \
> bat \
> “””;
> assert x.equals(“foo bar baz bat”);
>
> The single space before baz and the three spaces before bat are the left-hand
> leading spaces, not the ancillary spaces before the \ characters.
>
> If some of those trailing spaces are desirable, then \s can be used to make
> a fence that saves them from stripping.
>
> var x = “””
> foo bar\s \
> baz \s \
> bat\s \
> “””;
> assert x.equals(“foo bar baz bat ”);
>
> This rule decouples the two functions of \LT in the current proposal: (1) It joins
> lines, and (2) it creates a fence which makes previously ancillary spaces into
> real payload spaces. These are distinct jobs and should not be conflated.
> I think it’s a small but real improvement to separate the jobs, and allow \s
> to handle (2) and \LT to handle only (1).
>
> — John
>
> P.S. A variation of the above suggestion, probably less preferable, would delete
> spaces both *before* and *after* \LT, leading to this:
>
> var x = “””
> foo bar \
> baz \
> bat \
> “””;
> assert x.equals(“foo barbazbat”);
>
> Again, \s could save spaces from stripping.
>
>
More information about the amber-spec-experts
mailing list