using ++ and --

[berci]

Hi all!

I have a question: in standard C would it be possible to use the following:

++i--;

or as I would like to use it:

x ( a[ ++i-- ] ) ;

where i and a global vars, and x calls itself recursively.

I tried with 2 compilers, but both found it to be erroneous. But is it erroneous in standard C?

[codingmaster]

No it doesn't work, why do u wanna write such code???

your code is not valid C!!!

u can use something like:

int x=0;
++x,x--;

but at the end x=x+(1-1);
so it's equal to x=x

there is no sense for writing such code, or gimme an example, or write down what u wanna do......

[berci]

Thank you!

the example was that i wrote above, calling a function with a global variable so that fuction is called with the increased value, but when it returns, global variable would be the same as you wrote.

Of course, I can do it with one more line, but I was wondering...

[DavT]

Doesn't this do what you want?

x( a[i+1] );

no need for an extra line...

[berci]

no, it wouldn't do what it supposed, and actually my version is bad, too...

the correct, what i really need is:

i++;
x ( a [ i-1 ] );
i--;

so, call with i-th element of "a", but increase i before calling and decrease after.

[DavT]

ok, so explain how that is different from:

x( a[i] );

why do you feel the need to increment i before the call and decrement it afterwards? am i missing something else that you are trying to acheive as a side effect? consider this:

#include <stdio.h>

void x(unsigned v)
{
  printf("x() = %d\n", v);
}

int main (void)
{
  unsigned i = 2;
  unsigned a[] = {10,20,30,40};

  printf("your way...\n");
  i++;
  x( a[i-1] );
  i--;

  printf("\nmy way...\n");
  x( a[i] );

  printf("\nqed\n");

  return 0;
}

[berci]

Yes, exactly, i want to have that side effect, because i use it in a special environment, where i must save wherever i can. I have less then 1k for variables...

otherwise i could make it this way:

x(a[i],++i);
i--;

or if I declare i as local
x(a[i],i+1);