# Escape Sequences For Managing Whitespace (Preview)

Jim Laskey james.laskey at oracle.com
Thu Aug 15 15:32:39 UTC 2019

s/What does do you do here?/What so you do here/

> On Aug 15, 2019, at 12:19 PM, Jim Laskey <james.laskey at oracle.com> wrote:
>
> Assuming the proposal is <LWS* \ LWS* LWS> (keep last white space), I see the light but I see the dark here as well (and maybe not enough here to switch horses.)
>
> String hexData = """
>             000102030405060708090a0b0c0d0e0f101112131415   \
>     161718191a1b1c1d1e1f202122232425262728292a2b2c \
>     2d2e2f303132333435363738393a3b3c3d3e3f40       \
>     4142434445464748494a4b4c4d4e4f505152535455     \
>     """;
>
> This sort of pattern is high maintenance; aligning backslashes. I think a style guide would likely discourage this as a general pattern (even though I like the aesthetics.) I tend to favour the Jim patterns you mentioned, mostly because they are precise. There is no question here about what is kept and what is discarded.
>
> String story = """
>     "When I use a word," Humpty Dumpty said, \
>     in rather a scornful tone, "it means just what I \
>     choose it to mean - neither more nor less.”
>     "The question is," said Alice, "whether you \
>     can make words mean so many different things."
>     "The question is," said Humpty Dumpty, \
>     "which is to be master - that's all."
>     """;
> String story = """
>     "When I use a word," Humpty Dumpty said,\
>      in rather a scornful tone, "it means just what I\
>      choose it to mean - neither more nor less.”
>     "The question is," said Alice, "whether you\
>      can make words mean so many different things."
>     "The question is," said Humpty Dumpty,\
>      "which is to be master - that's all."
>     """;
>
> There is a another case which you didn't mention;
>
> String story = """
>     "When I use a word," Humpty Dumpty said,\
>     in rather a scornful tone, "it means just what I\
>     choose it to mean - neither more nor less.”\
>
>        "The question is," said Alice, "whether you\
>     can make words mean so many different things."\
>
>        "The question is," said Humpty Dumpty,\
>     "which is to be master - that's all."
>     """;
> What does do you do here? Do you stop at the second line terminator and, if so, what happens to the white space on the next line. This is where precision would make it cleaner/clearer.
>
> THE one case where your proposal wins for me is when used with the string literals. As proposed in the JEP, we have to continue string literals immediately at the left margin.
>
>     String str = "A line that may need to \
> continue on the next line.";
>
> Using your proposal we could do the following;
>
>     String str = "A line that may need to \
>                   continue on the next line.";
>
> Cheers,
>
> -- Jim
>
>
>
>> On Aug 14, 2019, at 5:55 PM, John Rose <john.r.rose at oracle.com <mailto:john.r.rose at oracle.com>> wrote:
>>
>> On Aug 13, 2019, at 10:29 AM, John Rose <john.r.rose at oracle.com <mailto:john.r.rose at oracle.com>> wrote:
>>>
>>> So I suggest deleting all of <LWS* \ LT LWS*> where LWS is either space or tab, unescaped of course.
>>>
>>
>> Just to be clear about my suggestion for stripping additional incidental whitespace before
>> and/or after <\ LT>, here’s an example for using a rule that expand stripping:
>>
>> String story = """
>>     "When I use a word," Humpty Dumpty said,         \
>>      in rather a scornful tone, "it means just what I \
>>      choose it to mean - neither more nor less.”
>>     "The question is," said Alice, "whether you      \
>>      can make words mean so many different things."
>>     "The question is," said Humpty Dumpty,           \
>>      "which is to be master - that's all."
>>     """;
>>
>> Here, all the spaces *before* the backslashes are treated as incidental.  They are beneficial
>> in allowing the programmer to lay them out separately from the content.  The dots show
>> which spaces are incidental (in both existing rules and under my suggestion)l:
>>
>> String story = """
>> ...."When I use a word," Humpty Dumpty said,.........\
>> .... in rather a scornful tone, "it means just what I.\
>> .... choose it to mean - neither more nor less.”
>> ...."The question is," said Alice, "whether you......\
>> .... can make words mean so many different things."
>> ...."The question is," said Humpty Dumpty,...........\
>> .... "which is to be master - that's all."
>> ....""";
>>
>> Here is the same content but without the extra incidental spaces, which conforms to the current
>> proposal by Jim:
>>
>>
>> String story = """
>>     "When I use a word," Humpty Dumpty said, \
>>     in rather a scornful tone, "it means just what I \
>>     choose it to mean - neither more nor less.”
>>     "The question is," said Alice, "whether you \
>>     can make words mean so many different things."
>>     "The question is," said Humpty Dumpty, \
>>     "which is to be master - that's all."
>>     """;
>>
>> Equivalently, and a bit more legibly, and also within the bounds of Jim's proposal:
>>
>> String story = """
>>     "When I use a word," Humpty Dumpty said,\
>>      in rather a scornful tone, "it means just what I\
>>      choose it to mean - neither more nor less.”
>>     "The question is," said Alice, "whether you\
>>      can make words mean so many different things."
>>     "The question is," said Humpty Dumpty,\
>>      "which is to be master - that's all."
>>     """;
>>
>> The intended content is, of course:
>> String story = """
>>     "When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean - neither more nor less.”
>>     "The question is," said Alice, "whether you can make words mean so many different things."
>>     "The question is," said Humpty Dumpty, "which is to be master - that's all."
>>     """;
>>
>> Incidental space could also be stripped after <\ LT> as well as before.  I think that the value of aligning
>> the backslashes is the main benefit here, so stripping *before* <\ LT> is more important than after.
>> But stripping incidentals after would allow the programmer to lay out continuation lines at a different
>> left margin, which can also be a help to readability, although the <\ s> sequences undo the benefit:
>>
>>
>> String story = """
>>     "When I use a word," Humpty Dumpty said,         \
>>          \sin rather a scornful tone, "it means just what I \
>>          \schoose it to mean - neither more nor less.”
>>     "The question is," said Alice, "whether you      \
>>          \scan make words mean so many different things."
>>     "The question is," said Humpty Dumpty,           \
>>          \s"which is to be master - that's all."
>>     """;
>>
>> So I’ll amend my suggestion to something a little trickier:  <LWS* \ LT> is stripped
>> as incidental whitespace, but in the case of <LWS* \ LT LWS* LWS>, the final character
>> of linear whitespace (aka horizontal whitespace) is significant content, not incidental.
>> This allows the obscuring <\ s> to be removed in the example:
>>
>>
>> String story = """
>>     "When I use a word," Humpty Dumpty said,         \
>>          in rather a scornful tone, "it means just what I \
>>          choose it to mean - neither more nor less.”
>>     "The question is," said Alice, "whether you      \
>>          can make words mean so many different things."
>>     "The question is," said Humpty Dumpty,           \
>>          "which is to be master - that's all."
>>     """;
>>
>> Here is the extra incidental space marked as dots:
>>
>> String story = """
>> ...."When I use a word," Humpty Dumpty said,.........\
>> ........ in rather a scornful tone, "it means just what I.\
>> ........ choose it to mean - neither more nor less.”
>> ...."The question is," said Alice, "whether you......\
>> ........ can make words mean so many different things."
>> ...."The question is," said Humpty Dumpty,...........\
>> ........ "which is to be master - that's all."
>> ....""";
>>
>> The suggested rule allows the author to adjust the broken line endings for maximum readability,
>> and the elision of the incidental space flows with them.
>>
>> Meanwhile, if the content has no spaces (perhaps it’s some kind fo binary resource) the user
>> cannot indent the continuation lines, but can still space out the backslash into a proudly separate
>> position from the content:
>>
>> String hexData = """
>>             000102030405060708090a0b0c0d0e0f101112131415   \
>>     161718191a1b1c1d1e1f202122232425262728292a2b2c \
>>     2d2e2f303132333435363738393a3b3c3d3e3f40       \
>>     4142434445464748494a4b4c4d4e4f505152535455     \
>>     """;
>> assert !hexData.contains(" ");
>>
>> The basic motivation should be clear:  Give users tools to lay out delimiters clearly separate
>> from content.  Whether it’s worth adding the extra twist to the rule about <\ LT> I will leave for
>> others to decide.
>>
>> HTH.
>>
>> — John
>

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