Could we add \a as an escape sequence for bell?

[David Alayachew]

❤️

David Alayachew reacted via Gmail
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On Mon, Oct 27, 2025 at 6:53 PM Pavel Rappo <pavel.rappo at gmail.com> wrote:

> On Mon, Oct 27, 2025 at 9:19 PM David Alayachew
> <davidalayachew at gmail.com> wrote:
> >
> > Woah, thanks.
> >
> > So, in your second example, it's literally complaining because, as far
> as the Java compiler is concerned, I typed in a literal new line in between
> the single quotes, right? Like this?
> >
> > System.out.println('
> > ');
> >
> > Correct?
>
> Yes.
>
> > Very important context, ty vm.
> >
> > So, \7 is fine because that actually is an escape sequence. Much like \n
> and friends.
>
> Yes. BTW, another way to write down \n would be \12:
>
>     jshell> Integer.toOctalString('\n')
>     $1 ==> "12"
>
>     jshell> '\n' == '\12'
>     $2 ==> true
>
> > But \uXXXX gets turned into the literal bytes, which means that
> something like a new line gets treated as if I literally pressed the new
> line button on my keyboard, which means that it's treated not as a new line
> character in my string, but as a new line character in my source file
> itself lol.
> >
> > Ty vm.
>
> Like I said, escape sequences are only recognised in certain context.
> But unicode escapes are recognised everywhere. For example, \n does
> not mean anything in a javadoc comment, On the other hand, \u000A
> means the same thing wherever it appears: source, javadoc, or your
> copyright header. Still, \n and \u000A are not the same:
>
>     jshell> '\n' == '\u000A'
>
>     |  Error:
>     |  illegal line end in character literal
>     |  '\n' == '\u000A'
>     |          ^
>
> -Pavel
>
>
> -Pavel
>
> > On Mon, Oct 27, 2025, 9:44 AM Pavel Rappo <pavel.rappo at gmail.com> wrote:
> >>
> >> Correcting a typo*:
> >>
> >>     jshell> System.out.println('\u000A')
> >>     |  Error:
> >>     |  illegal line end in character literal
> >>     |  System.out.println('\u000A')
> >>     |
> >>
> >>
> >> On Mon, Oct 27, 2025 at 1:32 PM Pavel Rappo <pavel.rappo at gmail.com>
> wrote:
> >> >
> >> > A word of caution. While in this use case the difference is probably
> >> > non-essential, Unicode escapes (e.g. \u0007) are __not__ a kind of
> >> > escape sequences (e.g. \7). The former are translated into raw bytes
> >> > __before__ the compiler goes any further. The latter are recognised by
> >> > the compiler only in context of character literals, strings, or text
> >> > blocks.
> >> >
> >> > To illustrate the difference, let's consider "line feed" (0xA):
> >> >
> >> >     jshell> System.out.println('\n')
> >> >
> >> >
> >> >
> >> >     jshell> System.out.println('\000A')
> >> >     |  Error:
> >> >     |  unclosed character literal
> >> >     |  System.out.println('\000A')
> >> >     |                     ^
> >> >
> >> > While the former is recognised within the context of a character
> >> > literal, the latter just breaks the source code in a similar way as if
> >> > the source code had the actual line feed in it.
> >> >
> >> > Unicode escapes allow you to simply input a Unicode character "by
> >> > reference". This is convenient in some cases, such as when your
> >> > environment cannot output these characters conveniently or display
> >> > them properly.
> >> >
> >> > -Pavel
> >> >
> >> > On Mon, Oct 27, 2025 at 12:56 PM David Alayachew
> >> > <davidalayachew at gmail.com> wrote:
> >> > >
> >> > > Ah, I misread the JLS Language Grammar!
> >> > >
> >> > > I was aware of \u0007, but not \7. I see now that that works. Then
> nevermind, that meets my needs just fine. No need for my suggestion.
> >> > >
> >> > > The 4 digit unicode is fine, a good escape hatch, but also easy to
> forget, since my brain interprets all 4 digits as significant. And char
> bell = 7; is also unideal. But a 1 digit escape works perfectly for me.
> Would have preferred \a, but \7 is more explicit and easier to look up.
> >> > >
> >> > > Ty vm!
> >> > >
> >> > > On Mon, Oct 27, 2025, 6:15 AM Andrew Dinn <adinn at redhat.com> wrote:
> >> > >>
> >> > >>
> >> > >>
> >> > >> On 26/10/2025 17:26, David Alayachew wrote:
> >> > >> > Also, here is the JLS 25 entry about escape sequences -- https://
> >> > >> > docs.oracle.com/javase/specs/jls/se25/html/jls-3.html#jls-3.10.7
> >> > >> > <
> https://docs.oracle.com/javase/specs/jls/se25/html/jls-3.html#jls-3.10.7>
> >> > >> >
> >> > >> > All I really want is for that to be added to the list, so that I
> can do
> >> > >> > it the same as I would in other languages. It sounds like an
> in-place
> >> > >> > replacement done by the compiler.
> >> > >>
> >> > >> What is wrong with using \u0007 or \7? (as documented in the html
> page
> >> > >> you cited).
> >> > >>
> >> > >> regards,
> >> > >>
> >> > >>
> >> > >> Andrew Dinn
> >> > >> -----------
> >> > >> Red Hat Distinguished Engineer
> >> > >> He/Him/His
> >> > >> IBM UK Limited
> >> > >> Registered in England and Wales with number 741598
> >> > >> Registered office: Building C, IBM Hursley Office, Hursley Park
> Road,
> >> > >> Winchester, Hampshire SO21 2JN
> >> > >>
> >>
>
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