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There is no "continue" for switch?

xz
Guest
  
Posts: n/a
#1: Mar 18 '08
What if I want the following:

vector<intv;

// v is loaded by push_back()

switch( v.size() ) {
case 2:
//do something

case 4:
//somehow delete two element
//and then do the same thing as in case 2

case 6:
//somehow delete two element
//and then do the same thing as in case 4

default:
//...
}


I thought using "continue" to implement this but got this:

continue statement not within a loop
Jerry Coffin
Guest
  
Posts: n/a
#2: Mar 18 '08

re: There is no "continue" for switch?

In article <7864a589-19a7-458d-99cd-
2611d772e4bd@x41g2000hsb.googlegroups.com>, zhang.xi.cn@gmail.com
says...
Quote:
What if I want the following:
>
vector<intv;
>
// v is loaded by push_back()
>
switch( v.size() ) {
case 2:
//do something
>
case 4:
//somehow delete two element
//and then do the same thing as in case 2
>
case 6:
//somehow delete two element
//and then do the same thing as in case 4
>
default:
//...
}
Correct -- continue works for loops by not switches. Fortunately you
don't need anything quite that difficult:

switch (v.size()) {
case 6:
// somehow delete two element (sic)
case 4:
// somehow delete two element
case 2:
// do something
}

If there isn't a break at the end of a block, execution will flow
through to the next block...

--
Later,
Jerry.

The universe is a figment of its own imagination.
Junchen WANG
Guest
  
Posts: n/a
#3: Mar 18 '08

re: There is no "continue" for switch?

On 3月18日, 下午11时46分, xz <zhang.xi...@gmail.com>wrote:
Quote:
What if I want the following:
>
vector<intv;
>
// v is loaded by push_back()
>
switch( v.size() ) {
case 2:
//do something
>
case 4:
//somehow delete two element
//and then do the same thing as in case 2
>
case 6:
//somehow delete two element
//and then do the same thing as in case 4
>
default:
//...
>
}
>
I thought using "continue" to implement this but got this:
>
continue statement not within a loop
please detail your intent.
xz
Guest
  
Posts: n/a
#4: Mar 18 '08

re: There is no "continue" for switch?

On Mar 18, 10:57 am, Jerry Coffin <jcof...@taeus.comwrote:
Quote:
In article <7864a589-19a7-458d-99cd-
2611d772e...@x41g2000hsb.googlegroups.com>, zhang.xi...@gmail.com
says...
>
>
>
Quote:
What if I want the following:
>
Quote:
vector<intv;
>
Quote:
// v is loaded by push_back()
>
Quote:
switch( v.size() ) {
case 2:
//do something
>
Quote:
case 4:
//somehow delete two element
//and then do the same thing as in case 2
>
Quote:
case 6:
//somehow delete two element
//and then do the same thing as in case 4
>
Quote:
default:
//...
}
>
Correct -- continue works for loops by not switches. Fortunately you
don't need anything quite that difficult:
>
switch (v.size()) {
case 6:
// somehow delete two element (sic)
case 4:
// somehow delete two element
case 2:
// do something
>
}
>
If there isn't a break at the end of a block, execution will flow
through to the next block...
well, I gave a case not so tough, what if a case a little tougher?

vector<intv;

// v is loaded by push_back()

switch( v.size() ) {
case 2:
//do something

case 4:
//somehow delete two element
//and then do the same thing as in case 2

case 6:
//somehow delete *four* element
//and then do the same thing as in case 2

default:
//...

}

i.e. I want to go to case 2 both after I treat the case 4 and case 6.

Quote:
>
--
Later,
Jerry.
>
The universe is a figment of its own imagination.
Junchen WANG
Guest
  
Posts: n/a
#5: Mar 18 '08

re: There is no "continue" for switch?

On 3月19日, 上午12时21分, xz <zhang.xi...@gmail.com>wrote:
Quote:
On Mar 18, 10:57 am, Jerry Coffin <jcof...@taeus.comwrote:
>
>
>
Quote:
In article <7864a589-19a7-458d-99cd-
2611d772e...@x41g2000hsb.googlegroups.com>, zhang.xi...@gmail.com
says...
>
Quote:
Quote:
What if I want the following:
>
Quote:
Quote:
vector<intv;
>
Quote:
Quote:
// v is loaded by push_back()
>
Quote:
Quote:
switch( v.size() ) {
case 2:
//do something
>
Quote:
Quote:
case 4:
//somehow delete two element
//and then do the same thing as in case 2
>
Quote:
Quote:
case 6:
//somehow delete two element
//and then do the same thing as in case 4
>
Quote:
Quote:
default:
//...
}
>
Quote:
Correct -- continue works for loops by not switches. Fortunately you
don't need anything quite that difficult:
>
Quote:
switch (v.size()) {
case 6:
// somehow delete two element (sic)
case 4:
// somehow delete two element
case 2:
// do something
>
Quote:
}
>
Quote:
If there isn't a break at the end of a block, execution will flow
through to the next block...
>
well, I gave a case not so tough, what if a case a little tougher?
>
vector<intv;
>
// v is loaded by push_back()
>
switch( v.size() ) {
case 2:
//do something
>
case 4:
//somehow delete two element
//and then do the same thing as in case 2
>
case 6:
//somehow delete *four* element
//and then do the same thing as in case 2
>
default:
//...
>
}
>
i.e. I want to go to case 2 both after I treat the case 4 and case 6.
>
>
>
>
>
Quote:
--
Later,
Jerry.
>
Quote:
The universe is a figment of its own imagination.- 隐藏被引用文字 -
>
- 显示引用的文字 -- 隐藏被引用文字 -
>
- 显示引用的文字 -
void f()
{
// do something
}

....
vector<intv;


// v is loaded by push_back()


switch( v.size() ) {
case 2:
f();//do something
break;


case 4:
//somehow delete two element
f();//and then do the same thing as in case 2
break;


case 6:
//somehow delete *four* element
f();//and then do the same thing as in case 2
break;

default:
//...
}
Christopher
Guest
  
Posts: n/a
#6: Mar 18 '08

re: There is no "continue" for switch?

Quote:
well, I gave a case not so tough, what if a case a little tougher?
>
vector<intv;
>
// v is loaded by push_back()
while(v.size() != 2)
{
Quote:
switch( v.size() ) {
case 2:
//do something
>
case 4:
//somehow delete two element
//and then do the same thing as in case 2
>
case 6:
//somehow delete *four* element
//and then do the same thing as in case 2
>
default:
//...
>
}
}
Quote:
i.e. I want to go to case 2 both after I treat the case 4 and case 6.

Or if you _always_ want to delete elements until the size is 2, I
wouldn't use a switch at all.

while(v.size() != 2)
{
// Determine which element to delete
// delete it
}
Victor Bazarov
Guest
  
Posts: n/a
#7: Mar 18 '08

re: There is no "continue" for switch?

xz wrote:
Quote:
What if I want the following:
>
vector<intv;
>
// v is loaded by push_back()
>
switch( v.size() ) {
case 2:
//do something
>
case 4:
//somehow delete two element
//and then do the same thing as in case 2
>
case 6:
//somehow delete two element
//and then do the same thing as in case 4
>
default:
//...
}
>
>
I thought using "continue" to implement this but got this:
>
continue statement not within a loop
I believe you should rearrange your clauses and make '6' and
'4' fall through to the '2':

switch (v.size()) {
case 6:
// somehow delete 2 elements
// and FALL THROUGH
case 4:
// somehow delete 2 elements
// and FALL THROUGH
case 2:
// do something
break; // Yes, only here

default:
//...
}

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask
Paul Brettschneider
Guest
  
Posts: n/a
#8: Mar 18 '08

re: There is no "continue" for switch?

xz wrote:
Quote:
What if I want the following:
>
vector<intv;
>
// v is loaded by push_back()
>
switch( v.size() ) {
case 2:
//do something
>
case 4:
//somehow delete two element
//and then do the same thing as in case 2
>
case 6:
//somehow delete two element
//and then do the same thing as in case 4
>
default:
//...
}
>
>
I thought using "continue" to implement this but got this:
>
continue statement not within a loop
Of course there is a continue for switch (for your example else-thread):

#include <iostream>

void f(uint8_t n)
{
std::cout << n << '\n';
switch(n) {
for(;;) {
case 2:
std::cout << "do_something\n";
break;
case 4:
std::cout << "somehow delete 2 elements\n";
continue;
case 6:
std::cout << "somehow delete 4 elements\n";
continue;
default:
std::cout << "default\n";
break;
}
}
}

int main()
{
f(2);
f(4);
f(6);
f(1);
}

HTH,
Paul
Paul Brettschneider
Guest
  
Posts: n/a
#9: Mar 18 '08

re: There is no "continue" for switch?

Paul Brettschneider wrote:
Quote:
xz wrote:
>
Quote:
>What if I want the following:
>>
>vector<intv;
>>
>// v is loaded by push_back()
>>
>switch( v.size() ) {
>case 2:
>//do something
>>
>case 4:
>//somehow delete two element
>//and then do the same thing as in case 2
>>
>case 6:
>//somehow delete two element
>//and then do the same thing as in case 4
>>
>default:
>//...
>}
>>
>>
>I thought using "continue" to implement this but got this:
>>
> continue statement not within a loop
>
Of course there is a continue for switch (for your example else-thread):
>
#include <iostream>
>
void f(uint8_t n)
{
std::cout << n << '\n';
switch(n) {
for(;;) {
case 2:
std::cout << "do_something\n";
break;
case 4:
std::cout << "somehow delete 2 elements\n";
continue;
case 6:
std::cout << "somehow delete 4 elements\n";
continue;
default:
std::cout << "default\n";
break;
}
}
}
>
int main()
{
f(2);
f(4);
f(6);
f(1);
}
Of course this doesn't do what you what it to do - it doesn't recompute the
label to jump to. Sorry, I'm tired.
Paul Brettschneider
Guest
  
Posts: n/a
#10: Mar 18 '08

re: There is no "continue" for switch?

Paul Brettschneider wrote:
Quote:
Paul Brettschneider wrote:
>
Quote:
>xz wrote:
>>
Quote:
>>What if I want the following:
>>>
>>vector<intv;
>>>
>>// v is loaded by push_back()
>>>
>>switch( v.size() ) {
>>case 2:
>>//do something
>>>
>>case 4:
>>//somehow delete two element
>>//and then do the same thing as in case 2
>>>
>>case 6:
>>//somehow delete two element
>>//and then do the same thing as in case 4
>>>
>>default:
>>//...
>>}
>>>
>>>
>>I thought using "continue" to implement this but got this:
>>>
>> continue statement not within a loop
>>
>Of course there is a continue for switch (for your example else-thread):
>>
>#include <iostream>
>>
>void f(uint8_t n)
>{
> std::cout << n << '\n';
> switch(n) {
> for(;;) {
> case 2:
> std::cout << "do_something\n";
> break;
> case 4:
> std::cout << "somehow delete 2 elements\n";
> continue;
> case 6:
> std::cout << "somehow delete 4 elements\n";
> continue;
> default:
> std::cout << "default\n";
> break;
> }
> }
>}
>>
>int main()
>{
> f(2);
> f(4);
> f(6);
> f(1);
>}
>
Of course this doesn't do what you what it to do - it doesn't recompute
the label to jump to. Sorry, I'm tired.
Here is the correct solution (I think):

#include <iostream>

void f(int n)
{
std::cout << n << '\n';
for(;;) {
switch(n) {
case 2:
std::cout << "do_something\n";
break;
case 4:
std::cout << "somehow delete 2 elements\n";
n -= 2;
continue;
case 6:
std::cout << "somehow delete 4 elements\n";
n -= 4;
continue;
default:
std::cout << "default\n";
break;
}
break;
}
}

int main()
{
f(2);
f(4);
f(6);
f(1);
}
Jerry Coffin
Guest
  
Posts: n/a
#11: Mar 19 '08

re: There is no "continue" for switch?

In article <01db3ce8-2e5e-470d-a892-
0e0771bc98ff@b1g2000hsg.googlegroups.com>, zhang.xi.cn@gmail.com says...

[ ... ]
Quote:
well, I gave a case not so tough, what if a case a little tougher?
>
vector<intv;
>
// v is loaded by push_back()
>
switch( v.size() ) {
case 2:
//do something
>
case 4:
//somehow delete two element
//and then do the same thing as in case 2
>
case 6:
//somehow delete *four* element
//and then do the same thing as in case 2
>
default:
//...
>
}
>
i.e. I want to go to case 2 both after I treat the case 4 and case 6.
Truth to tell, I doubt I'd use switch at all for this. Rather, I'd do
something like this:

if (x == 2 || x == 4 || x == 6) {
v.erase(v.begin()+2, v.begin()+x-2);
// do something
}
else
// whatever was in your default.

Of course, you'll probably need to make minor changes to account for the
position in the vector where you want to do the deletion.

--
Later,
Jerry.

The universe is a figment of its own imagination.
Alexander Dong Back Kim
Guest
  
Posts: n/a
#12: Mar 19 '08

re: There is no "continue" for switch?

On Mar 19, 2:46 am, xz <zhang.xi...@gmail.comwrote:
Quote:
What if I want the following:
>
vector<intv;
>
// v is loaded by push_back()
>
switch( v.size() ) {
case 2:
//do something
>
case 4:
//somehow delete two element
//and then do the same thing as in case 2
>
case 6:
//somehow delete two element
//and then do the same thing as in case 4
>
default:
//...
>
}
>
I thought using "continue" to implement this but got this:
>
continue statement not within a loop
Hi Zhang,

It seems you wanna to something like spaghetti code can do. Are you
originally from Basic language? =) I think Junchen's approach is a
right way to do it.

Cheers,
Alex
Alexander Dong Back Kim
Guest
  
Posts: n/a
#13: Mar 19 '08

re: There is no "continue" for switch?

On Mar 19, 9:32 am, Paul Brettschneider <paul.brettschnei...@yahoo.fr>
wrote:
Quote:
xz wrote:
Quote:
What if I want the following:
>
Quote:
vector<intv;
>
Quote:
// v is loaded by push_back()
>
Quote:
switch( v.size() ) {
case 2:
//do something
>
Quote:
case 4:
//somehow delete two element
//and then do the same thing as in case 2
>
Quote:
case 6:
//somehow delete two element
//and then do the same thing as in case 4
>
Quote:
default:
//...
}
>
Quote:
I thought using "continue" to implement this but got this:
>
Quote:
continue statement not within a loop
>
Of course there is a continue for switch (for your example else-thread):
>
#include <iostream>
>
void f(uint8_t n)
{
std::cout << n << '\n';
switch(n) {
for(;;) {
case 2:
std::cout << "do_something\n";
break;
case 4:
std::cout << "somehow delete 2 elements\n";
continue;
case 6:
std::cout << "somehow delete 4 elements\n";
continue;
default:
std::cout << "default\n";
break;
}
}
>
}
>
int main()
{
f(2);
f(4);
f(6);
f(1);
>
}
>
HTH,
Paul
I didn't know that ;)

Cheers,
jason.cipriani@gmail.com
Guest
  
Posts: n/a
#14: Mar 19 '08

re: There is no "continue" for switch?

On Mar 18, 6:42 pm, Paul Brettschneider <paul.brettschnei...@yahoo.fr>
wrote:
Quote:
Paul Brettschneider wrote:
Here is the correct solution (I think):
Yes; it works. Although I think using "goto" would have actually been
clearer here... at least with goto you know that it's going to jump
somewhere and you have to look for a label; whereas with your solution
I found that I first consulted the standard to verify that "continue"
was not for "switch" before looking very closely to see the "for (;;)"
hidden in there.


Jason

Quote:
>
#include <iostream>
>
void f(int n)
{
std::cout << n << '\n';
for(;;) {
switch(n) {
case 2:
std::cout << "do_something\n";
break;
case 4:
std::cout << "somehow delete 2 elements\n";
n -= 2;
continue;
case 6:
std::cout << "somehow delete 4 elements\n";
n -= 4;
continue;
default:
std::cout << "default\n";
break;
}
break;
}
>
}
>
int main()
{
f(2);
f(4);
f(6);
f(1);
>
}
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