How would you write this?

[aleksa]

do {
skip: val = *src++; if (val == 1) goto skip;

*dst++ = val;
} while (val != 2);

I'm copying from src to dst all values except ONE and I stop when TWO
is copied.

How to write this so there is no "skip" label?
Or, how do I jump to the beginning of the DO/WHILE loop?

I've tried BREAK/CONTINUE:
break jumps outside of the loop.
continue jumps to the decision point (val != 2)
and what I would like is to jump to the beginning of the do/while loop.

 

[Tim Rentsch]

do {
skip: val = *src++; if (val == 1) goto skip;

*dst++ = val;
} while (val != 2);

I'm copying from src to dst all values except ONE and I stop when TWO
is copied.

How to write this so there is no "skip" label?
Or, how do I jump to the beginning of the DO/WHILE loop?

I've tried BREAK/CONTINUE:
break jumps outside of the loop.
continue jumps to the decision point (val != 2)
and what I would like is to jump to the beginning of the do/while loop.

do {
while( *src == 1 ) src++;
*dst++ = *src++;
} while( dst[-1] != 2 );

 

[David RF]

do {
    skip: val = *src++; if (val == 1) goto skip;

    *dst++ = val;

} while (val != 2);

I'm copying from src to dst all values except ONE and I stop when TWO
is copied.

How to write this so there is no "skip" label?
Or, how do I jump to the beginning of the DO/WHILE loop?

I've tried BREAK/CONTINUE:
 break jumps outside of the loop.
 continue jumps to the decision point (val != 2)
and what I would like is to jump to the beginning of the do/while loop.

while ((val = *src++) != 1);

 

[David RF]

while ((val = *src++) != 1);

Excuse me:
while ((val = *src++) == 1);

 

[Jean-Christophe]

On Apr 24, 9:54 pm, aleksa

do { skip: val = *src++; if (val == 1) goto skip;
    *dst++ = val;
} while (val != 2);

do
{ if( (val = *src++) != 1 ) *dst++ = val;
} while (val != 2);


// note that if the src buffer is large, it's
// better to use memcpy for faster performance.

 

[Francois Grieu]

do {
skip: val = *src++; if (val == 1) goto skip;

*dst++ = val;
} while (val != 2);

I'm copying from src to dst all values except ONE and I stop when TWO
is copied.

How to write this so there is no "skip" label?
Or, how do I jump to the beginning of the DO/WHILE loop?

I've tried BREAK/CONTINUE:
break jumps outside of the loop.
continue jumps to the decision point (val != 2)
and what I would like is to jump to the beginning of the do/while loop.

Hint1: do loops can be nested.

Hint2: in the context, "continue" does what just you ask, albeit not
optimally for many (if not most) compilers as we know them today. Which
is a pity, if you ask.

Hint3: if you really want a single loop and be able to jump at the
beginning without a goto, there are "for(;{;}", "while(1){;}", or
"do{;}while(1), with the exit condition using break.

Francois Grieu

 

[Peter Nilsson]

do {
    skip: val = *src++; if (val == 1) goto skip;

    *dst++ = val;

} while (val != 2);

I'm copying from src to dst all values except ONE and I
stop when TWO is copied.

How to write this so there is no "skip" label?

while ((val = *src++) == 1 || (*dst++ = val) != 2)
;

 

[spinoza1111]

"Peter Nilsson" <[email protected]> ha scritto nel messaggio


i whould write it so:
    goto  b;
m:  ++dst
a:  ++src;
b:  val=*src; if(val==1) goto a;
    *dst=val;
    if(val!=2)  goto  m;



  while ((val = *src++) == 1 || (*dst++ = val) != 2)
    ;

it is unreadable to me

Then, with all due respect, consider learning to read code before you
write code.

 

[aleksa]

Thanks everyone.

My taste is "hint 1" from Francois Grieu:

do {
do {val = *src++;} while (val == 1);
*dst++ = val;
} while (val != 2);

 

[Paul N]

do {
    skip: val = *src++; if (val == 1) goto skip;

    *dst++ = val;

} while (val != 2);

I'm copying from src to dst all values except ONE and I stop when TWO
is copied.

How to write this so there is no "skip" label?
Or, how do I jump to the beginning of the DO/WHILE loop?

I've tried BREAK/CONTINUE:
 break jumps outside of the loop.
 continue jumps to the decision point (val != 2)
and what I would like is to jump to the beginning of the do/while loop.

Perhaps I'm missing something, but what's wrong with the following?

do {
val = *src++;
if (val != 1) *dst++ = val;
} while (val != 2);

No label required, and no nested loops. It jumps to the beginning of
the loop by getting to the end. Or is your actual code slightly
different from what you posted, and you want to avoid the test for
some reason?

 

[Willem]

Richard wrote:
)> do {
)> val = *src++;
)> if (val != 1) *dst++ = val;
)> } while (val != 2);
)>
)> No label required, and no nested loops. It jumps to the beginning of
)> the loop by getting to the end. Or is your actual code slightly
)> different from what you posted, and you want to avoid the test for
)> some reason?
)>
)
) Much better.
)
) But I prefer this. Only check for 2 when we know its not 1 ...
)
) for(int val=0;{
) if ((val=*src++)!= 1)
) if((*dst++=val)==2)
) break;
) }
)
) I think. Not compiled. Not tested blah blah blah ...

Nah, I would expect any compiler to optimize this out anyway.


SaSW, Willem
--
Disclaimer: I am in no way responsible for any of the statements
made in the above text. For all I know I might be
drugged or something..
No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT

 

[Tim Rentsch]

while ((val = *src++) == 1 || (*dst++ = val) != 2)
;

This suggests another alternative

do *dst = *src++; while( *dst == 1 || *dst++ != 2);

 

[Phil Carmody]

This suggests another alternative

do *dst = *src++; while( *dst == 1 || *dst++ != 2);

I have on my desk at work an architecture where your version
would do very much the wrong thing.

Micro-spoilerette - the things that aren't seen are the
things that are important.

Rest of spoiler in headers.

Phil

 

[Tim Rentsch]

I have on my desk at work an architecture where your version
would do very much the wrong thing.

Micro-spoilerette - the things that aren't seen are the
things that are important.

Yes, I wrote my alternative presuming that 'volatile' wasn't
involved. Stylistically, I think it's better not to use an
extra variable if it isn't needed, and it doesn't seem to be
here. Also I expect that anyone who knows what volatile is can
make the necessary adjustments if volatile accesses are a
factor.

For that matter, 'val' could be volatile, in which case Peter's
rewrite also behaves differently from the original.