digitalmars.D.bugs - [Issue 7133] New: [tdpl] There should be no empty statement
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http://d.puremagic.com/issues/show_bug.cgi?id=7133
Summary: [tdpl] There should be no empty statement
Product: D
Version: D2
Platform: Other
OS/Version: Mac OS X
Status: NEW
Severity: normal
Priority: P2
Component: DMD
AssignedTo: nobody puremagic.com
ReportedBy: andrei metalanguage.com
--- Comment #0 from Andrei Alexandrescu <andrei metalanguage.com> 2011-12-18
18:17:17 PST ---
The statement ";" should not exist. It is never needed, never useful, and in
most cases the compiler requires it to be replaced with '{}'.
Walter and I agreed on all of the above so ";" is not present in TDPL. It
should be slowly deprecated and ultimately removed from D. It is just junk in
the trunk.
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Jonathan M Davis <jmdavisProg gmx.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jmdavisProg gmx.com
--- Comment #1 from Jonathan M Davis <jmdavisProg gmx.com> 2011-12-18 18:25:35
PST ---
The one case that I'm aware of where some have argued for its value is labels.
e.g.
LABEL:;
Since labels require a statement, ; makes it so that you can you can use a
label without really having a statement. I'm not sure that that merits keeping
it however, since in every other use case that I can think of, it has no value.
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--- Comment #3 from Jonathan M Davis <jmdavisProg gmx.com> 2011-12-18 18:28:18
PST ---
I didn't think that that worked, since {} isn't a statement (at least, as far
as I know, it isn't), but if it works, it's certainly better.
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--- Comment #4 from Andrei Alexandrescu <andrei metalanguage.com> 2011-12-18
20:06:48 PST ---
{} is the empty statement in D.
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--- Comment #5 from Jonathan M Davis <jmdavisProg gmx.com> 2011-12-18 20:11:40
PST ---
Is that different from C++? I thought that {} was just an empty scope without
any statements in it at all in both C/C++ and D.
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Stewart Gordon <smjg iname.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |smjg iname.com
Platform|Other |All
OS/Version|Mac OS X |All
Severity|normal |enhancement
--- Comment #6 from Stewart Gordon <smjg iname.com> 2011-12-19 05:07:21 PST ---
(In reply to comment #5)
Is that different from C++? I thought that {} was just an empty scope without
any statements in it at all in both C/C++ and D.
It is, but in 100% of cases the compiler can optimise away that empty scope and
so it's equivalent to an empty statement.
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Dec 19 2011
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jakobovrum gmail.com changed:
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CC| |jakobovrum gmail.com
--- Comment #7 from jakobovrum gmail.com 2011-12-19 05:16:39 PST ---
(In reply to comment #3)
I didn't think that that worked, since {} isn't a statement (at least, as far
as I know, it isn't), but if it works, it's certainly better.
It is indeed a statement, it's called a block statement, also in D:
http://dlang.org/statement.html#BlockStatement
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timon.gehr gmx.ch changed:
What |Removed |Added
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CC| |timon.gehr gmx.ch
--- Comment #8 from timon.gehr gmx.ch 2011-12-19 06:23:35 PST ---
(In reply to comment #0)
The statement ";" should not exist. It is never needed, never useful, and in
most cases the compiler requires it to be replaced with '{}'.
Walter and I agreed on all of the above so ";" is not present in TDPL. It
should be slowly deprecated and ultimately removed from D. It is just junk in
the trunk.
I think it is useful. This looks odd:
int i = 2;
for({} i<2; i++){}
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--- Comment #9 from Stewart Gordon <smjg iname.com> 2011-12-19 07:17:31 PST ---
(In reply to comment #8)
I think it is useful. This looks odd:
int i = 2;
for({} i<2; i++){}
The ; you're replacing there isn't a statement - it's something explicitly
allowed by the ForStatement syntax.
ForStatement:
for (Initialize Testopt ; Incrementopt) ScopeStatement
Initialize:
;
NoScopeNonEmptyStatement
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Don <clugdbug yahoo.com.au> changed:
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--- Comment #10 from Don <clugdbug yahoo.com.au> 2011-12-24 04:41:20 PST ---
(In reply to comment #2)
LABEL: {}
is as good and marginally nicer.
Bear in mind that it only ever happens at the end of a block, so the next
character is always a }.
The existing label syntax needs to be retained for asm statements, though,
since they don't have {}.
asm {
jmp done;
done:
;
}
which is already ugly, and will look really silly when nude ; statements are
gone. I wish we could get rid of that silly semicolon.
In fact the oddity is that labels are considered to be statements, yet they
don't end with a semicolon.
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Dec 24 2011
http://d.puremagic.com/issues/show_bug.cgi?id=7133 --- Comment #11 from Jakob Ovrum <jakobovrum gmail.com> 2011-12-25 01:03:29 PST --- (In reply to comment #10)In fact the oddity is that labels are considered to be statements, yet they don't end with a semicolon.Block, if, while, do, for, foreach, switch, with, etc. Most types of statements don't end with a semicolon. Remember that the label statement is: Identifier : NoScopeStatement The following statement is a sub-statement of the label statement. It's not any more inconsistent than other statements with sub-statements. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Dec 25 2011
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Walter Bright <bugzilla digitalmars.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |bugzilla digitalmars.com
Resolution| |FIXED
--- Comment #12 from Walter Bright <bugzilla digitalmars.com> 2011-12-29
02:23:17 PST ---
I've added a warning for empty statements, but left the ; after the label as
allowed.
https://github.com/D-Programming-Language/dmd/commit/39d850a65ea5766a7cbd7bbe2fc8ed8e784fcdee
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