Question on switch

[Ian Tuomi]

Is it possible to go through multiple cases in one case like this? how?

switch(foo)
{
case 1 or 2:
dosomething(); break; //dosomething if foo is either 1 or 2

case 3:
dosomethingelse (); break; // dosomethingelse if foo is 3
}

--
Ian Tuomi
Jyväskylä, Finland

"Very funny scotty, now beam down my clothes."

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[Default User]

Ian Tuomi wrote:

Oh, thanks! BTW I have the K&R C book but my friend is borrowing it.

Oh, so you HAD K&R. You'll never see it again ;)


Brian Rodenborn

[Default User]

Ian Tuomi wrote:

Oh, thanks! BTW I have the K&R C book but my friend is borrowing it.

Oh, so you HAD K&R. You'll never see it again ;)


Brian Rodenborn

[Steve Zimmerman]

Ian Tuomi wrote:

Is it possible to go through multiple cases in one case like this? how?

switch(foo)
{
case 1 or 2:
dosomething(); break; //dosomething if foo is either 1 or 2

case 3:
dosomethingelse (); break; // dosomethingelse if foo is 3
}

Thank you for your post, Ian.

Yes, it is possible through a technique called "fall through."

switch(foo)
{
case 1:
case 2: dosomething();
break;
...
}

The compiler will automatically execute dosomething() and break for
cases 1 and 2 You can include however many cases you want with this
technique, for example,

switch(foo)
{
case 1: /* cases 1 through 4 "fall through" to case 5 */
case 2:
case 3:
case 4:
case 5: dosomething();
break;
...
}

Cases may also be written horizontally instead of vertically, as
follows.

switch(foo)
{
case 1: case 2: case 3: case 4:
case 5: dosomething();
break;
...
}

--Steve

[Dik T. Winter]

In article <bk**********@p hys-news1.kolumbus. fi> Ian Tuomi <ia*******@co.j yu.fi> writes:

Andreas Kahari wrote:

Yes:

switch (foo) {
case 1: /* FALLTROUGH /*
case 2:
bar();
break;

I'm alittle confused now.
Looking at that piece of code it looks like in case 1 nothing is done
and to access bar() it would require that foo = 2

What am I missing?

You are missing that C differs from (for instance) Pascal. In C
statements are executed after a case until a break is encountered
or the end of the complete switch statement is reached.
--
dik t. winter, cwi, kruislaan 413, 1098 sj amsterdam, nederland, [phone]
home: bovenover 215, 1025 jn amsterdam, nederland; http://www.cwi.nl/~dik/

[Irrwahn Grausewitz]

"Dik T. Winter" <Di********@cwi .nl> wrote:

In article <bk**********@p hys-news1.kolumbus. fi> Ian Tuomi <ia*******@co.j yu.fi> writes:

Andreas Kahari wrote:

Yes:

switch (foo) {
case 1: /* FALLTROUGH /*
case 2:
bar();
break;

I'm alittle confused now.
Looking at that piece of code it looks like in case 1 nothing is done
and to access bar() it would require that foo = 2

What am I missing?

You are missing that C differs from (for instance) Pascal. In C
statements are executed after a case until a break is encountered
or the end of the complete switch statement is reached.

Right, and for a good (or was it bad?!?) example lookup
question 20.35: What is "Duff's Device"? in the c.l.c-faq:

http://www.eskimo.com/~scs/C-faq/top.html

Regards

Irrwahn
--
Great minds run in great circles.

[Jack Klein]

On Wed, 24 Sep 2003 16:41:28 +0000 (UTC), Andreas Kahari
<ak*******@free shell.org> wrote in comp.lang.c:

In article <bk**********@p hys-news1.kolumbus. fi>, Ian Tuomi wrote:

Andreas Kahari wrote:

switch (foo) {
case 1: /* FALLTROUGH /*

Oops, ended the comment with /* instead of with */

I'm alittle confused now.
Looking at that piece of code it looks like in case 1 nothing is done
and to access bar() it would require that foo = 2

The case doesn't close until it's broken.

There are at least two exceptions:

switch(some_val )
{
case 1:
some_func();
case 2:
some_other_func ();
/* goto some_label_outs ide_switch */ <- uncomment this line */
yet_another_fun ction();
} <- both cases close here, no break

some_label_outs ide_switch:
++some_val;

--
Jack Klein
Home: http://JK-Technology.Com
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