The Lounge - CodeProject

Stefan_Lang3-Aug-14 23:50

3-Aug-14 23:50

At this point I think we're down to the question of personal preference. Every language has some features that people like and are missing in other languages. People preferring those other languages may not consider those features as desirable. Maybe because the typical tasks they work on have no use for it, or maybe because the programming guidelines they're used to would not leave room for them.

Me, I don't see a need for exitwhile/exitfor in C/C++. I see sufficient alternatives, and while the risk for abuse is nowhere near the risk of statements like goto or #define macros, I'd still prefer to avoid it at the cost of slightly more verbose conditional code.

Then again, I'm biased by the kind of code I usually work with: there's no day that passes without me having to skim over unfamiliar code, so everything that isn't obvious from a quick glance on the code, makes it harder for me to do my job. Therefore I prefer the conditions listed in one place, at the start (or in case of a do loop, at the end) of the loop. Having to scan the entire loop body to find out what conditions may have caused the loop to end just means extra work for me. Therefore I try to avoid break and continue (not to mention goto). And for the same reason I wouldn't welcome exitwhile/exitfor.

GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)

Re: Loop exit

Eduard Matei31-Jul-14 0:59

Eduard Matei

31-Jul-14 0:59

"Are there other languages out there with something similar?"

Python has this "syntactic sugar" for alternate loop exit:

Python

for item in iterable:
    if condition(item):
        break
    process(item)
else:
    print("No item in iterable meets the condition")

The else signifies that the for loop has finished without "break"-ing.

Re: Loop exit

Matthew Barnett31-Jul-14 1:20

Matthew Barnett

31-Jul-14 1:20

In Python, loops can take an 'else' clause. It's run if you don't break out of the loop.

For example:

Python

for item in collection:
    if some_test(item):
        print('Found one!')
        break
else:
    print('No match found.')

Re: Loop exit

kalberts31-Jul-14 23:11

kalberts

31-Jul-14 23:11

Yes, this is in the right direction. As your example illustrate, you do not have a symmetrical handling of the two ways out of the loop: The "breakout handling" is embedded in the loop code. with no syntactical indication that it is anything but ordinary actions within the loop. The 'else' provides half of what I want, and half is far better than nothing Smile | :)

Re: Loop exit

M. Eugene Andrews31-Jul-14 1:53

M. Eugene Andrews

31-Jul-14 1:53

Visual Basic.NET supports similar constructs, such as:

Exit For
Exit While
Exit Do

and continuations like:

Continue For
Continue While
Continue Do

Re: Loop exit

crazedDotNetDev31-Jul-14 5:59

crazedDotNetDev

31-Jul-14 5:59

In fact I seem to remember an "exit for" in QBASIC. Loop exits go way back in many BASIC compliers.

But all you C# coders don't worry; you're still "the best". You'll become better coders as C# becomes more like BASIC. WTF | :WTF:

LOL, sorry couldn't help myself. Blush | :O

- great coders make code look easy

- When humans are doing things computers could be doing instead, the computers get together late at night and laugh at us. - ¿Neal Ford?

Re: Loop exit

kalberts31-Jul-14 22:58

kalberts

31-Jul-14 22:58

But does it provide two ways out? I.e. alternate code blocks executed one but not the other, depending on how you exited the loop?

Re: Loop exit

crazedDotNetDev1-Aug-14 10:34

crazedDotNetDev

1-Aug-14 10:34

It depended on the specific language’s implementation. The general rule was it exits from the innermost loop. I seem to remember VB (pre .NET) was able to break from nested loops…

do while true
  for i = 1 to 10
    if i > 5 then
      exit do
    end if
  next
loop

I also got something rattling around in my skull about exiting from named loops, but I don’t believe that was a BASIC language. Google/Bing isn’t being helpful at the moment. Frown | :(

- great coders make code look easy

- When humans are doing things computers could be doing instead, the computers get together late at night and laugh at us. - ¿Neal Ford?

Re: Loop exit

Member 460889831-Jul-14 5:58

Member 4608898

31-Jul-14 5:58

But if you had

for (...) {
for (...) {
I want to exitfor from the outer loop from a condition in the inner loop
}
}

How would you do it? goto was invented for a reason and this is it!!! Big Grin | :-D

Re: Loop exit

kalberts31-Jul-14 22:57

kalberts

31-Jul-14 22:57

CHILL has a very nice solution to this: Every block, whether a procedure, loop, switch or even a linear sequence of statements enclosed with BEGIN and END, could be prefixed with a label. In CHILL, a label does not identify a point in the program, but a block, and consequently label scopes could be nested. So to leave the outer loop, you would write

SQL

OuterLoop: 
DO FOR (...) 

   InnerLoop: 
   DO FOR (...) 
      ...
      IF <done processing this element> THEN EXIT InnerLoop; FI;
      ...
      IF <some fatal condition> THEN EXIT OuterLoop; FI
      ...
   OD

OD

(Here I illustrate both leaving the inner loop and the outer loop.) However, CHILL doesn't provide what I asked for in my original post: If the post-loop processing depends on whether you completed the loop or left prematurely by EXIT, you must set some variable to a magic value and test it after the loop, and the post-loop processing would syntactically (e.g. with respect to variable scope) be outside the loop.

While we are at CHILL: Another nifty syntactic sugar cube is the keyword EVER:

C++

DO FOR EVER
   ...
OD

The semantics of EVER is quite obvious. I like this so much that whenever I need to program an inner loop in C, I set up a

C++

#define ever (;;)

to be able to code it as "for ever {...}" in C.

Sure, any well seasoned C programmer would prefer "while (1) {...}", but even though I have been writing more lines of C code than in any other language the last thirty years, I still read it as "while one what???"

Re: Loop exit

dg6yhw1131-Jul-14 7:25

dg6yhw11

31-Jul-14 7:25

BASIC provides several exit statements such as

EXIT LOOP
EXIT FOR

You can also set the condition in the call to the loop

WHILE Not [answer you want is found] ... WEND will exit when the condition is met (of course you have to add another exit test to avoid infinite loops Smile | :)

There are a bunch of similar constructs.

To use this with some OOP type language just write a little function in BASIC (Visual Studio, PowerBasic), compile to a DLL and call it from the object you need to use.

Visual Studio would probably let you do it all in the same project but then you wouldn't have the DLL to reuse.

Re: Loop exit

Frank Malcolm31-Jul-14 15:40

Frank Malcolm

31-Jul-14 15:40

Delphi's version of Pascal has Break (quit the loop) and Continue (begin the next iteration).

Re: Loop exit

kalberts31-Jul-14 22:19

kalberts

31-Jul-14 22:19

That is like break and continue in C, isn't it?

Does it provide two alternatative ways out of a loop: One alternative is executed if the break was performed,the other if break was not performed? If it does, some more syntax must be defined.

Re: Loop exit

Frank Malcolm1-Aug-14 13:57

Frank Malcolm

1-Aug-14 13:57

I don't know C well enough to comment.

And yes, if you need to know whether you exited the loop because of the break or the for/while/repeat condition, you have to code it separately.

Usually there's some "natural" way to easily determine that, but obviously not always.

Doing an interview today

glennPattonWork329-Jul-14 22:49

glennPattonWork3

29-Jul-14 22:49

Hi All,
The first interview (for some time). Not really sure about it, they haven't really told me or the agent what they will ask (please no Labview)...
GLENN (Also my first post from my S3)

Re: Doing an interview today

Argonia29-Jul-14 22:50

Argonia

29-Jul-14 22:50

I am wishing you the best of luck and please tell us how it went when its done Smile | :)

Microsoft ... the only place where VARIANT_TRUE != true

Re: Doing an interview today

glennPattonWork329-Jul-14 22:57

glennPattonWork3

29-Jul-14 22:57

Thanks

Re: Doing an interview today

OriginalGriff29-Jul-14 22:50

OriginalGriff

29-Jul-14 22:50

Good luck, my friend! Thumbs Up | :thumbsup:

I'm sure you won't need it...you'll be fine.

Those who fail to learn history are doomed to repeat it. --- George Santayana (December 16, 1863 – September 26, 1952)
Those who fail to clear history are doomed to explain it. --- OriginalGriff (February 24, 1959 – ∞)

Re: Doing an interview today

glennPattonWork329-Jul-14 22:55

glennPattonWork3

29-Jul-14 22:55

Thanks, The s3 Is a little odd to post with!

Re: Doing an interview today

Kornfeld Eliyahu Peter29-Jul-14 22:54

Kornfeld Eliyahu Peter

29-Jul-14 22:54

All the best!

I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is. (V)

Re: Doing an interview today