• Michel Colman (21/21) Sep 05 2012 I have a very simple suggestion for breaking out of nested loops.
• Piotr Szturmaj (5/6) Sep 05 2012 I think it's already there: http://dlang.org/statement.html#BreakStateme...
• monarch_dodra (5/14) Sep 05 2012 I really wish there was a simple "break from current scope"
• Piotr Szturmaj (4/16) Sep 05 2012 break scope [Identifier];
• Regan Heath (23/35) Sep 05 2012 You can lodge an enhancement request, example code:
• monarch_dodra (4/7) Sep 05 2012 Good idea actually.
• monarch_dodra (5/15) Sep 05 2012 Yeah.. Don't click that link...
• Jose Armando Garcia (7/42) Sep 05 2012 Haven't tried it but this maybe implementable using templates, try and
• monarch_dodra (5/62) Sep 05 2012 It is implementable with a simple "label: do{}while(false);"
• ixid (6/6) Sep 05 2012 A goto is actually better than "break 3" because you can modify

"Michel Colman" <michelcolman mac.com> writes:

I have a very simple suggestion for breaking out of nested loops.

Currently, there are a few ways of breaking out of multiple 
nested loops but they all have unnecessary drawbacks:
- exceptions (performance penalty, complexity)
- using boolean flags that are checked in every iteration 
(performance hit)
- goto (ugly, generally frowned apon, although this is often 
cited as one of the few cases where using goto is actually 
acceptable, which says a lot about the lack of other options)

I propose an extremely simple solution that is probably very easy 
to implement in compilers:

break break; // breaks out of two loops
break break break; // breaks out of three loops
break break continue; // jumps to the end of the third enclosing 
loop

You might also introduce a shorthand version for breaking out of 
a whole lot of loops:
break 5; // breaks out of 5 loops

And, why not,
break 5 continue; // jumps to the end of the sixth enclosing loop

What do you think?

Piotr Szturmaj <bncrbme jadamspam.pl> writes:

Michel Colman wrote:
 I have a very simple suggestion for breaking out of nested loops.

I think it's already there: http://dlang.org/statement.html#BreakStatement

"If break is followed by Identifier, the Identifier must be the label of 
an enclosing while, for, do or switch statement, and that statement is 
exited. It is an error if there is no such statement."

"monarch_dodra" <monarchdodra gmail.com> writes:

On Wednesday, 5 September 2012 at 12:43:26 UTC, Piotr Szturmaj 
wrote:
 Michel Colman wrote:
 I have a very simple suggestion for breaking out of nested 
 loops.

 I think it's already there: 
 http://dlang.org/statement.html#BreakStatement

 "If break is followed by Identifier, the Identifier must be the 
 label of an enclosing while, for, do or switch statement, and 
 that statement is exited. It is an error if there is no such 
 statement."

I really wish there was a simple "break from current scope" 
command. It would be kinda like "goto end of scope", just 
cleaner...

Piotr Szturmaj <bncrbme jadamspam.pl> writes:

monarch_dodra wrote:
 On Wednesday, 5 September 2012 at 12:43:26 UTC, Piotr Szturmaj wrote:
 Michel Colman wrote:
 I have a very simple suggestion for breaking out of nested loops.

 I think it's already there:
 http://dlang.org/statement.html#BreakStatement

 "If break is followed by Identifier, the Identifier must be the label
 of an enclosing while, for, do or switch statement, and that statement
 is exited. It is an error if there is no such statement."

 I really wish there was a simple "break from current scope" command. It
 would be kinda like "goto end of scope", just cleaner...

break scope [Identifier];

Uses two known keywords and (IMHO) looks good. Just file a feature 
request and wait :)

"Regan Heath" <regan netmail.co.nz> writes:

On Wed, 05 Sep 2012 13:55:32 +0100, monarch_dodra <monarchdodra gmail.com>  
wrote:

 On Wednesday, 5 September 2012 at 12:43:26 UTC, Piotr Szturmaj wrote:
 Michel Colman wrote:
 I have a very simple suggestion for breaking out of nested loops.

 I think it's already there:  
 http://dlang.org/statement.html#BreakStatement

 "If break is followed by Identifier, the Identifier must be the label  
 of an enclosing while, for, do or switch statement, and that statement  
 is exited. It is an error if there is no such statement."

 I really wish there was a simple "break from current scope" command. It  
 would be kinda like "goto end of scope", just cleaner...

You can lodge an enhancement request, example code:

void main()
{
	label: {
	  // ..code..
	  writefln("code1");
	  writefln("break..");
	  break label;  // jumps to "here:"
	  // ..code..
	  writefln("code2");
	}
	// break lands here
	writefln("here");
}

Current error:
   test.d(nn): Error: enclosing label 'label' for break not found

In fact, as any BlockStatement can be labeled you can argue any  
BlockStatement label should be 'breakable'.

R

-- 
Using Opera's revolutionary email client: http://www.opera.com/mail/

"monarch_dodra" <monarchdodra gmail.com> writes:

On Wednesday, 5 September 2012 at 13:13:14 UTC, Regan Heath wrote:
 You can lodge an enhancement request, example code:

 [SNIP]

 R

Good idea actually.

http://d.puremagic.com/issues/post_bug.cgi

posted as enhancement request for DMD (this is correct, right?)

"monarch_dodra" <monarchdodra gmail.com> writes:

On Wednesday, 5 September 2012 at 13:36:48 UTC, monarch_dodra 
wrote:
 On Wednesday, 5 September 2012 at 13:13:14 UTC, Regan Heath 
 wrote:
 You can lodge an enhancement request, example code:

 [SNIP]

 R

 Good idea actually.

 http://d.puremagic.com/issues/post_bug.cgi

 posted as enhancement request for DMD (this is correct, right?)

Yeah.. Don't click that link...

THIS is the correct link:
http://d.puremagic.com/issues/show_bug.cgi?id=8622

Jose Armando Garcia <jsancio gmail.com> writes:

On Sep 5, 2012, at 6:13, "Regan Heath" <regan netmail.co.nz> wrote:

 On Wed, 05 Sep 2012 13:55:32 +0100, monarch_dodra <monarchdodra gmail.com 
 wrote:

 On Wednesday, 5 September 2012 at 12:43:26 UTC, Piotr Szturmaj wrote:
 Michel Colman wrote:
 I have a very simple suggestion for breaking out of nested loops.

 I think it's already there: http://dlang.org/statement.html#BreakStatement

 "If break is followed by Identifier, the Identifier must be the  
 label of an enclosing while, for, do or switch statement, and that  
 statement is exited. It is an error if there is no such statement."

 I really wish there was a simple "break from current scope"  
 command. It would be kinda like "goto end of scope", just cleaner...

 You can lodge an enhancement request, example code:

 void main()
 {
    label: {
      // ..code..
      writefln("code1");
      writefln("break..");
      break label;  // jumps to "here:"
      // ..code..
      writefln("code2");
    }
    // break lands here
    writefln("here");
 }

 Current error:
  test.d(nn): Error: enclosing label 'label' for break not found

 In fact, as any BlockStatement can be labeled you can argue any  
 BlockStatement label should be 'breakable'.

Haven't tried it but this maybe implementable using templates, try and  
catch.

I say this because Scala, being a "functional" language implements  
this as a library using closure, high order function, try, catch and  
throw. Maybe a few other features.

-jose
 R

 -- 
 Using Opera's revolutionary email client: http://www.opera.com/mail/

"monarch_dodra" <monarchdodra gmail.com> writes:

On Wednesday, 5 September 2012 at 15:12:11 UTC, Jose Armando 
Garcia wrote:
 On Sep 5, 2012, at 6:13, "Regan Heath" <regan netmail.co.nz> 
 wrote:

 On Wed, 05 Sep 2012 13:55:32 +0100, monarch_dodra 
 <monarchdodra gmail.com
 wrote:

 On Wednesday, 5 September 2012 at 12:43:26 UTC, Piotr 
 Szturmaj wrote:
 Michel Colman wrote:
 I have a very simple suggestion for breaking out of nested 
 loops.

 I think it's already there: 
 http://dlang.org/statement.html#BreakStatement

 "If break is followed by Identifier, the Identifier must be 
 the label of an enclosing while, for, do or switch 
 statement, and that statement is exited. It is an error if 
 there is no such statement."

 I really wish there was a simple "break from current scope" 
 command. It would be kinda like "goto end of scope", just 
 cleaner...

 You can lodge an enhancement request, example code:

 void main()
 {
   label: {
     // ..code..
     writefln("code1");
     writefln("break..");
     break label;  // jumps to "here:"
     // ..code..
     writefln("code2");
   }
   // break lands here
   writefln("here");
 }

 Current error:
 test.d(nn): Error: enclosing label 'label' for break not found

 In fact, as any BlockStatement can be labeled you can argue 
 any BlockStatement label should be 'breakable'.

 Haven't tried it but this maybe implementable using templates, 
 try and catch.

 I say this because Scala, being a "functional" language 
 implements this as a library using closure, high order 
 function, try, catch and throw. Maybe a few other features.

 -jose
 R

 --
 Using Opera's revolutionary email client: 
 http://www.opera.com/mail/


It is implementable with a simple "label: do{}while(false);" 
actually.

... Or a goto ...

"ixid" <nuaccount gmail.com> writes:

A goto is actually better than "break 3" because you can modify 
inner loops and the goto will still take you to the right place, 
the "break 3" would take you to the wrong place if you change the 
number of loops. There's nothing wrong with goto in this context 
and as others have said we already have break label and continue 
label which either break or continue the labelled loop.