• Linden Krouse (54/54) Jan 03 2013 My proposal is for a slight addition to for and foreach
• Tobias Pankrath (5/36) Jan 03 2013 Python has a very similar thing, where you can have an else after
• qznc (5/10) Jan 03 2013 Interesting. I was thinking about such a language feature myself
• Linden Krouse (2/7) Jan 03 2013 "then" and "else could be changed to something more descriptive,
• Tobias Pankrath (2/10) Jan 03 2013 I don't think any new keywords will make it into the language.
• bearophile (7/10) Jan 03 2013 I find the "else" of "for" sometimes handy in Python, but using
• deed (17/32) Jan 03 2013 How about using scope inside the loop?
• deed (3/3) Jan 03 2013 More descriptive:
• Timon Gehr (10/42) Jan 03 2013 Current solution:
• Nick Sabalausky (3/67) Jan 03 2013 Yea, I've occasionally found myself wishing we had those.

"Linden Krouse" <ztaticnull gmai.com> writes:

My proposal is for a slight addition to for and foreach 
statements by allowing different blocks of code to be executed 
whether the loop is exited from the condition failing or a break 
statement. These would of course be independently optional.
For example:

for(int num = 0; num < 10; num++)
{
     if(<condition>)
         break;
}
then
{
     //num successfully counted up to 10
     //do stuff...
}
else
{
     //loop was broken prematurely
     //do other stuff...
}

One instance where this would be useful is in situations when 
code should be executed if an item is not found while searching.
For example:

Current solution:

int[] nums = [1, 2, 3, 4, 5];
int i = 6;

bool intFound = false;
foreach(n; nums)
{
     if(n == i)
     {
         intFound = true;
         break;
     }
}

if(!intFound)
{
     //i was not found, do stuff
}

Using for/then/else:

int[] nums = [1, 2, 3, 4, 5];
int i = 6;

foreach(n; nums)
{
     if(n == i)
         break;
}
then
{
     //i was not found, do stuff
}

Not only would this be more compact and easier to read, but it 
should also be more efficient (less checking and less memory 
usage).

"Tobias Pankrath" <tobias pankrath.net> writes:

On Thursday, 3 January 2013 at 09:00:00 UTC, Linden Krouse wrote:
 Current solution:

 int[] nums = [1, 2, 3, 4, 5];
 int i = 6;

 bool intFound = false;
 foreach(n; nums)
 {
     if(n == i)
     {
         intFound = true;
         break;
     }
 }

 if(!intFound)
 {
     //i was not found, do stuff
 }

 Using for/then/else:

 int[] nums = [1, 2, 3, 4, 5];
 int i = 6;

 foreach(n; nums)
 {
     if(n == i)
         break;
 }
 then
 {
     //i was not found, do stuff
 }

 Not only would this be more compact and easier to read, but it 
 should also be more efficient (less checking and less memory 
 usage).

Python has a very similar thing, where you can have an else after 
a loop. However I always found it unintuitive whether the else 
branch gets executed if you break the loop or if you finish all 
iterations without breaking. Even now I'd have to look it up.

"qznc" <qznc go.to> writes:

On Thursday, 3 January 2013 at 09:00:00 UTC, Linden Krouse wrote:
 My proposal is for a slight addition to for and foreach 
 statements by allowing different blocks of code to be executed 
 whether the loop is exited from the condition failing or a 
 break statement. These would of course be independently 
 optional.

Interesting. I was thinking about such a language feature myself 
for some time.

Just a small extension to your proposal: It also applies to 
while-loop.

"Linden Krouse" <ztaticnull gmai.com> writes:

 Python has a very similar thing, where you can have an else 
 after a loop. However I always found it unintuitive whether the 
 else branch gets executed if you break the loop or if you 
 finish all iterations without breaking. Even now I'd have to 
 look it up.

"then" and "else could be changed to something more descriptive, 
they were just the first keywords that came to mind.

"Tobias Pankrath" <tobias pankrath.net> writes:

On Thursday, 3 January 2013 at 09:51:59 UTC, Linden Krouse wrote:
 Python has a very similar thing, where you can have an else 
 after a loop. However I always found it unintuitive whether 
 the else branch gets executed if you break the loop or if you 
 finish all iterations without breaking. Even now I'd have to 
 look it up.

 "then" and "else could be changed to something more 
 descriptive, they were just the first keywords that came to 
 mind.

I don't think any new keywords will make it into the language.

"bearophile" <bearophileHUGS lycos.com> writes:

Linden Krouse:

 "then" and "else could be changed to something more 
 descriptive, they were just the first keywords that came to 
 mind.

I find the "else" of "for" sometimes handy in Python, but using 
"else" for "unbroken" is not good enough. A more descriptive 
keyword is kind of needed here. But I don't think Walter wants to 
add new keywords to D now.

Bye,
bearophile

"deed" <none none.none> writes:

 for(int num = 0; num < 10; num++)
 {
     if(<condition>)
         break;
 }
 then
 {
     //num successfully counted up to 10
     //do stuff...
 }
 else
 {
     //loop was broken prematurely
     //do other stuff...
 }


How about using scope inside the loop?

for (int num = 0; num < 10; num++)
{
     // do stuff...

     if (<condition>)
         break;

     scope(loop_break)
     {
         // loop was broken prematurely
         // do other stuff...
     }

     scope(loop_finish)
     {
         //  num successfully counted up to 10
         //  do stuff...
     }
}

"deed" <none none.none> writes:

More descriptive:

scope(loop_interrupted)
scope(loop_completed)

"Timon Gehr" <timon.gehr gmx.ch> writes:

On Thursday, 3 January 2013 at 09:00:00 UTC, Linden Krouse wrote:
 ...

 Current solution:

 int[] nums = [1, 2, 3, 4, 5];
 int i = 6;

 bool intFound = false;
 foreach(n; nums)
 {
     if(n == i)
     {
         intFound = true;
         break;
     }
 }

 if(!intFound)
 {
     //i was not found, do stuff
 }

 Using for/then/else:

 int[] nums = [1, 2, 3, 4, 5];
 int i = 6;

 foreach(n; nums)
 {
     if(n == i)
         break;
 }
 then
 {
     //i was not found, do stuff
 }

 Not only would this be more compact and easier to read, but it 
 should also be more efficient (less checking and less memory 
 usage).

Current solution:

foreach(n;nums) if(n==i) goto Lfound;
// i was not found, do stuff
Lfound:;

I think that any more or less decent compiler back end ought to 
be able to transform your boolean flag code into this form. (If 
the foreach loop is executed sufficiently many times, it does not 
make any kind of meaningful difference anyways.) This proposal is 
about convenient syntax.

Nick Sabalausky <SeeWebsiteToContactMe semitwist.com> writes:

On Thu, 03 Jan 2013 09:59:59 +0100
"Linden Krouse" <ztaticnull gmai.com> wrote:

 My proposal is for a slight addition to for and foreach 
 statements by allowing different blocks of code to be executed 
 whether the loop is exited from the condition failing or a break 
 statement. These would of course be independently optional.
 For example:
 
 for(int num = 0; num < 10; num++)
 {
      if(<condition>)
          break;
 }
 then
 {
      //num successfully counted up to 10
      //do stuff...
 }
 else
 {
      //loop was broken prematurely
      //do other stuff...
 }
 
 One instance where this would be useful is in situations when 
 code should be executed if an item is not found while searching.
 For example:
 
 Current solution:
 
 int[] nums = [1, 2, 3, 4, 5];
 int i = 6;
 
 bool intFound = false;
 foreach(n; nums)
 {
      if(n == i)
      {
          intFound = true;
          break;
      }
 }
 
 if(!intFound)
 {
      //i was not found, do stuff
 }
 
 Using for/then/else:
 
 int[] nums = [1, 2, 3, 4, 5];
 int i = 6;
 
 foreach(n; nums)
 {
      if(n == i)
          break;
 }
 then
 {
      //i was not found, do stuff
 }
 
 Not only would this be more compact and easier to read, but it 
 should also be more efficient (less checking and less memory 
 usage).

Yea, I've occasionally found myself wishing we had those.