Does C# support anything like PHP's break command that optionally
accepts a parameter specifying how many loops to break out of?
accepts a parameter specifying how many loops to break out of?
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RE: Using "break&quo t; to Break Out of Multiple Loops in One Call
No - 'break' and 'continue' always apply to the innermost loop.
You will need to set and test flags to do what you want (or - gasp - goto).
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"O.B." wrote:
Does C# support anything like PHP's break command that optionally
accepts a parameter specifying how many loops to break out of?
> -
Re: Using "break&quo t; to Break Out of Multiple Loops in One Call
On 15 Feb, 18:31, "O.B." <funkj...@bells outh.netwrote:Not that Im aware of, and there would be grunts in the cleraing ofDoes C# support anything like PHP's break command that optionally
accepts a parameter specifying how many loops to break out of?
code if I found one...
for(;;int i(for(i=0;i<100 ;for(;console.w riteline("{0}\n ",i;for(;;i +
+for(;;break(2) )))));
have to try that... someday... it sholdnt work, but giving an example
of why not.. it should stop at writing nothing but who knows...
//CY
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Re: Using "break&quo t; to Break Out of Multiple Loops in One Call
O.B. wrote:No. And that's not very nice to begin with (requiring the programmer toDoes C# support anything like PHP's break command that optionally
accepts a parameter specifying how many loops to break out of?
count carefully). Labeled breaks a la Java would be better, but it doesn't
have that either.
If you really think it makes the code easier to read, you can always use
goto. If the "multi-level break" is to handle a rare error condition, you
could throw an exception instead. If that's the case, though, you should
probably split things up in multiple functions. That would also allow you to
use "return" to break out of all loops in the current function.
--
J.
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Re: Using "break&quo t; to Break Out of Multiple Loops in One Call
"Peter Duniho" <NpOeStPeAdM@nn owslpianmk.comw rote in
news:op.t6ld6ps z8jd0ej@petes-computer.local:
There's nothing bad in goto. I just love the longjmp() !!Either way, I don't think there's anything inherently bad about
labeled "break" statements or "goto" statements. Sometimes they are
just what you need. Just remember not to aim at your foot when using
them. :)
>
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Re: Using "break&quo t; to Break Out of Multiple Loops in One Call
On Fri, 15 Feb 2008 17:26:49 -0800, Donkey Hot <spam@plc.is-a-geek.com>
wrote:
Well, sure. But these days we have exceptions to provide for that.There's nothing bad in goto. I just love the longjmp() !!
In fact, I'd say if anything, the descendant of longjmp() is much more
broadly accepted than that of goto. :)
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Re: Using "break&quo t; to Break Out of Multiple Loops in One Call
"Peter Duniho" <NpOeStPeAdM@nn owslpianmk.comw rote in message
news:op.t6ld6ps z8jd0ej@petes-computer.local. ..Would you mind providing one such example?Personally, I'm not of the mind that "goto" statements are inherently
bad. They certainly can be misused, and may well be misused much more
than other language constructs. But they also have their place (and I
don't just mean as a replacement for falling through in "case" statements
:) ).
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Re: Using "break&quo t; to Break Out of Multiple Loops in One Call
On Sat, 16 Feb 2008 08:16:53 -0800, Scott Roberts
<sroberts@no.sp am.here-webworks-software.comwro te:
Well, one common scenario is error-handling. In some cases, it makes>
"Peter Duniho" <NpOeStPeAdM@nn owslpianmk.comw rote in message
news:op.t6ld6ps z8jd0ej@petes-computer.local. ..>>Personally, I'm not of the mind that "goto" statements are inherently
>bad. They certainly can be misused, and may well be misused much more
>than other language constructs. But they also have their place (and I
>don't just mean as a replacement for falling through in "case"
>statements :) ).
Would you mind providing one such example?
sense to have a single exit point in a method so that things can be
cleaned up in a single block of code rather than repeating that code, or
some subset, throughout the method. Using a "goto" statement allows you
to place that cleanup in a single place (I generally put it at the end of
the method), jumping to it on an error, and otherwise falling straight
through.
Nesting a bunch of "if()" statements can accomplish the same thing, but it
can create a difficult-to-read pattern of indentation. Using a "goto"
provides a lot of the same readability benefits that using exceptions for
failures can as well.
Are there other ways to do that? Sure, especially in C# (which has
"using" as well as exceptions). But those alternatives don't always
result in code that's as readable. And does the presence of those
alternatives mean that a "goto" statement is bad? No, not at all. Only
someone who had a blanket objection to using a "goto" statement for the
sake of the objection would say it was.
The fact is, even if you never write a "goto" statement, you use "goto"s
all the time. As long as you're keeping the code structured as you use a
"goto" statement, you haven't done anything the compiler wouldn't do
anyway. And if the use of the "goto" makes the code more readable, then
that's an advantage over shoe-horning your code into whatever alternative
the language would require to accomplish the same thing.
Pete
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Re: Using "break&quo t; to Break Out of Multiple Loops in One Call
On Feb 16, 3:11 pm, "Scott Roberts" <srobe...@no.sp am.here-webworks-
software.comwro te:I am not Peter Duniho but I can provide you an example from a real"Peter Duniho" <NpOeStPe...@nn owslpianmk.comw rote in message
>
news:op.t6mq92h e8jd0ej@petes-computer.local. ..
>
>
>>On Sat, 16 Feb 2008 08:16:53 -0800, Scott Roberts
<srobe...@no.sp am.here-webworks-software.comwro te:>"Peter Duniho" <NpOeStPe...@nn owslpianmk.comw rote in message
>news:op.t6ld6p sz8jd0ej@petes-computer.local. ..
>Personally, I'm not of the mind that "goto" statements are inherently
>bad. They certainly can be misused, and may well be misused much more
>than other language constructs. But they also have their place (and I
>don't just mean as a replacement for falling through in "case"
>statements :) ).>Would you mind providing one such example?
world high-performance middle-ware product. I lifted this piece out
of the codebase of this product (http://www.zeroc.com)
Consider this snippet that listens on a socket:
public static void doListen(Socket socket, int backlog)
{
repeatListen:
try
{
socket.Listen(b acklog);
}
catch(SocketExc eption ex)
{
if(interrupted( ex))
{
goto repeatListen;
}
closeSocketNoTh row(socket);
throw new Ice.SocketExcep tion(ex);
}
}
public static bool interrupted(Win 32Exception ex)
{
return ex.NativeErrorC ode == WSAEINTR;
}
There are probably other ways to do this without using goto but you
will only end up obfuscating the intent of the code for some mythical
purity.
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Re: Using "break&quo t; to Break Out of Multiple Loops in One Call
"Dilip" <rdilipk@lycos. comwrote in message
news:007a31b5-9dea-489b-9822-6c9532fd74ea@p2 5g2000hsf.googl egroups.com...Hmmm, here's my attempt, but you may be right. I'll admit that the originalOn Feb 16, 3:11 pm, "Scott Roberts" <srobe...@no.sp am.here-webworks-
software.comwro te:>>"Peter Duniho" <NpOeStPe...@nn owslpianmk.comw rote in message
>>
>news:op.t6mq92 he8jd0ej@petes-computer.local. ..
>>
>>
>>>>On Sat, 16 Feb 2008 08:16:53 -0800, Scott Roberts
<srobe...@no.sp am.here-webworks-software.comwro te:>>>"Peter Duniho" <NpOeStPe...@nn owslpianmk.comw rote in message
>>news:op.t6ld6 psz8jd0ej@petes-computer.local. ..
>>Personally, I'm not of the mind that "goto" statements are inherently
>>bad. They certainly can be misused, and may well be misused much
>>more
>>than other language constructs. But they also have their place (and
>>I
>>don't just mean as a replacement for falling through in "case"
>>statements :) ).>>>Would you mind providing one such example?
I am not Peter Duniho but I can provide you an example from a real
world high-performance middle-ware product. I lifted this piece out
of the codebase of this product (http://www.zeroc.com)
>
Consider this snippet that listens on a socket:
>
public static void doListen(Socket socket, int backlog)
{
repeatListen:
>
try
{
socket.Listen(b acklog);
}
catch(SocketExc eption ex)
{
if(interrupted( ex))
{
goto repeatListen;
}
>
closeSocketNoTh row(socket);
throw new Ice.SocketExcep tion(ex);
}
}
>
public static bool interrupted(Win 32Exception ex)
{
return ex.NativeErrorC ode == WSAEINTR;
}
>
There are probably other ways to do this without using goto but you
will only end up obfuscating the intent of the code for some mythical
purity.
>
is pretty good. Thanks for the example.
// The intent here should be pretty clear: keep calling
// "tryListen" until it returns "true". Although, it's not
// entirely clear *why* tryListen might return false.
public static void doListen(Socket socket, int backlog)
{
while (!tryListen(soc ket, backlog)) ;
// or
bool success = tryListen(socke t, backlog);
while (!success)
success = tryListen(socke t, backlog);
}
// The intent here may be a little obfuscated. It's not clear
// at all that you are going to retry if "interrupte d".
public static bool tryListen(Socke t socket, int backlog)
{
try
{
socket.Listen(b acklog);
}
catch(SocketExc eption ex)
{
if(interrupted( ex))
{
// Listen failed, try again.
return false;
}
closeSocketNoTh row(socket);
throw new Ice.SocketExcep tion(ex);
}
// Listen succeeded.
return true;
}
public static bool interrupted(Win 32Exception ex)
{
return ex.NativeErrorC ode == WSAEINTR;
}
Comment
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Re: Using "break&quo t; to Break Out of Multiple Loops in One Call
Dilip wrote:Hmm, I didn't know you could jump out of a try block with a goto, then re-enter>
I am not Peter Duniho but I can provide you an example from a real
world high-performance middle-ware product. I lifted this piece out
of the codebase of this product (http://www.zeroc.com)
>
Consider this snippet that listens on a socket:
>
public static void doListen(Socket socket, int backlog)
{
repeatListen:
>
try
{
socket.Listen(b acklog);
}
catch(SocketExc eption ex)
{
if(interrupted( ex))
{
goto repeatListen;
}
>
closeSocketNoTh row(socket);
throw new Ice.SocketExcep tion(ex);
}
}
>
public static bool interrupted(Win 32Exception ex)
{
return ex.NativeErrorC ode == WSAEINTR;
}
>
the block, very interesting...
How about:
public static void doListen(Socket socket, int backlog)
{
bool retry = true;
while (retry)
{
try
{
socket.Listen(b acklog);
retry = false;
}
catch(SocketExc eption ex)
{
if (!interrupted(e x))
{
closeSocketNoTh row(socket);
throw new Ice.SocketExcep tion(ex);
}
}
}
}
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Re: Using "break&quo t; to Break Out of Multiple Loops in One Call
Another situation is where a particular operation will invalidate the
data being processes. For instance
start:
Generate dataset
for( - data set - )
while (something something)
for( - dataset - )
if (something something)
{
something that invalidates dataset
goto start:
}
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