DaniWeb Forum Index > Software Development > C

C RSS

valid or not

Please support our C advertiser: Programming Forums - DaniWeb Sister Site

•

Join Date: Jul 2004

Posts: 31

Reputation: Sukhbir is an unknown quantity at this point

Solved Threads: 0

Sukhbir

Offline

Light Poster

valid or not

Aug 31st, 2004

consider the statement
++*p++
if it is valid then evaluate it.

•

Join Date: Mar 2004

Posts: 1,620

Reputation: kc0arf is a jewel in the rough

Solved Threads: 51

kc0arf

Offline

Posting Virtuoso

Re: valid or not

Aug 31st, 2004

Hello,

I am no C++ genius, but

++*p++

Cannot be a statement by itself, as there is no ; to finish it.

I am trying to remember if *p is significant. I know that &p is... the address of the variable p. p++ is just an incrementor. But C++ has been a "variable first, then operator" type of language. cars++ people--

I think it is an error.

Christian

•

Join Date: Apr 2004

Posts: 4,362

Reputation: Dave Sinkula has a brilliant future

Solved Threads: 241

Dave Sinkula Dave Sinkula is offline

Offline

long time no c

Re: valid or not

Aug 31st, 2004

Increment the object pointed to by p, then increment the pointer p (point to the next object).

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
#include <stdio.h>
 
  int main(void)
  {
     char text[] = "1b#", *p = text;
     printf("text = \"%s\", p(%p) = \"%s\", *p = '%c'\n", text, (void*)p, p, *p);
     ++*p++;
     printf("text = \"%s\", p(%p) = \"%s\", *p = '%c'\n", text, (void*)p, p, *p);
     return 0;
  }
 
  /* my output
  text = "1b#", p(0012FF88) = "1b#", *p = '1'
  text = "2b#", p(0012FF89) = "b#", *p = 'b'
  */
#include <stdio.h>
  
  int main(void)
  {
     char text[] = "1b#", *p = text;
     printf("text = \"%s\", p(%p) = \"%s\", *p = '%c'\n", text, (void*)p, p, *p);
     ++*p++;
     printf("text = \"%s\", p(%p) = \"%s\", *p = '%c'\n", text, (void*)p, p, *p);
     return 0;
  }
  
  /* my output
  text = "1b#", p(0012FF88) = "1b#", *p = '1'
  text = "2b#", p(0012FF89) = "b#", *p = 'b'
  */

Really, this code is trivial to come up with on your own. At least give these a try.

"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: Mar 2004

Posts: 1,620

Reputation: kc0arf is a jewel in the rough

Solved Threads: 51

kc0arf

Offline

Posting Virtuoso

Re: valid or not

Aug 31st, 2004

Hello,

I stand corrected. Reading another post in the forum, people apparently do use ++variable syntax. I always took the style of variable++ and went with it to avoid confusion.

So

++p would be valid.

++*p++ I think is a problem.

Christian

•

Join Date: Sep 2004

Posts: 185

Reputation: Stack Overflow is an unknown quantity at this point

Solved Threads: 4

Stack Overflow Stack Overflow is offline

Offline

C Programmer

Re: valid or not

Sep 1st, 2004

You could say its valid, though it really all depends on how or why its used:

Help with Code Tags

(Toggle Plain Text)

void pointTo(char **src, char *dst) {
	*src = dst;
}

int main() {
	char h[25];
	char *hello;

	pointTo(&hello, h);

	strcpy(h, "Hello world!");

	printf("%c\n", ++*hello++);

	return 0;
}

You could ask yourself, "Wow, how'd it come up with 'I'?", though its perfectly understandable. *hello++ is 'H', as the first letter of our string, though ++*hello++ moves our first letter 'H' one to the right, resulting in the next letter of the alphabet, 'I'.

Hope this makes sense,
- Stack Overflow

Following the rules will ensure you get a prompt answer to your question. If posting code, please include BB [code][/code] tags. Your question may have been asked before, try the search facility.

IRC
Channel: irc.daniweb.com
Room: #c, #shell

•

Join Date: Aug 2004

Posts: 22

Reputation: Decency is an unknown quantity at this point

Solved Threads: 1

Decency

Offline

Newbie Poster

Re: valid or not

Sep 1st, 2004

hello, well this is valid in C++ but you may try to do it in separate statements or store the results in separate pointers just to avoid the logical errors that might occur, always remember flexibility comes before simplisity