DaniWeb Forum Index > Software Development > C++

how do i sort reords from Z-A? (in turbo C)

Please support our C++ advertiser: Intel Parallel Studio Home

•

Join Date: Aug 2005

Posts: 15,629

Reputation: Ancient Dragon has a reputation beyond repute

Solved Threads: 1496

Ancient Dragon Ancient Dragon is offline

Offline

Still Learning

Re: how do i sort reords from Z-A? (in turbo C)

#11

Sep 19th, 2005

Oh! your right Dave -- because subtracting a minus is really addition. I knew that, just checking if you did too :cheesy: :o

•

Join Date: Aug 2005

Posts: 15,629

Reputation: Ancient Dragon has a reputation beyond repute

Solved Threads: 1496

Ancient Dragon Ancient Dragon is offline

Offline

Still Learning

Re: how do i sort reords from Z-A? (in turbo C)

#12

Sep 19th, 2005

•

Originally Posted by Dave Sinkula

Help with Code Tags

C++ Syntax (Toggle Plain Text)
int bar(const void *a, const void *b)
{
   const int *x = a, *y = b;
   return (*x > *y) - (*x < *y);
}
int bar(const void *a, const void *b) { const int *x = a, *y = b; return (*x > *y) - (*x < *y); }

That will not compile with either VC++ 6.0 or Dev-C++. Requires cast like this

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
int bar(const void *a, const void *b)
{
   const int *x = (int*)a, *y = (int*)b;
   return (*x > *y) - (*x < *y);
}
int bar(const void *a, const void *b)
{
   const int *x = (int*)a, *y = (int*)b;
   return (*x > *y) - (*x < *y);
}

but otherwise an interesting algorithm.

•

Join Date: Apr 2004

Posts: 4,459

Reputation: Dave Sinkula has a brilliant future

Solved Threads: 252

Dave Sinkula Dave Sinkula is offline

Offline

long time no c

Re: how do i sort reords from Z-A? (in turbo C)

#13

Sep 19th, 2005

Avoid compiling C code in a C++ compiler. (Or else save the file with a .c extension instead of .cpp!)

[edit]

•

but otherwise an interesting algorithm.

Yeah, I've been trying to Google the thing about 'no branches' or 'no instruction flush' or whatever it was -- something potentially beneficial to remember so that I could Google it again one day.

[edit=2]Here's another integer compare function that Narue might enjoy.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
int baz(const void *a, const void *b)
{
   const int *x = a, *y = b;
   return (*x < *y) ? -1 : (*x > *y);
}
int baz(const void *a, const void *b)
{
   const int *x = a, *y = b;
   return (*x < *y) ? -1 : (*x > *y);
}

[edit=3]And note that in all my posts to this thread, the comparison function when used with qsort would sort in increasing order -- rather than the OP's requested decreasing order.

Last edited by Dave Sinkula; Sep 19th, 2005 at 5:09 pm. Reason: Noting when I was finished editing.

"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary." --Ayn Rand

•

Join Date: Sep 2004

Posts: 7,847

Reputation: Narue has a reputation beyond repute

Solved Threads: 753

Narue

Offline

Senior Bitch

Re: how do i sort reords from Z-A? (in turbo C)

#14

Sep 19th, 2005

>So why bother in that comparison function I posted ?
Because pointers to void can be funny beasties. I like to make sure that everything matches up before the function call on the off chance that I miss a subtle issue. That's actually a throwback from when I didn't fully understand pointers and wrote code to protect myself from my own ignorance, but at the very least it proves that I know what types strcmp expects.