problem to undestand nested pointers

[happy]

Hello all, Below is a code snippet in C

#include<stdio.h>
int main (void)
{
static char *s[ ] = {“black”, “white”, “yellow”, “violet”};
char **ptr[ ] = {s+3, s+2, s+1, s}, ***p;
p = ptr;
**++p;
printf(“%s\n”,*--*++p + 3);
return 0;
}

I am getting some problem in understanding output of this problem.
Here initially, p contains
address of first element of ptr i.e. &(s+3), then due to ++p, p is &(s
+2).
Now I can't understand how the term *--*++p in printf is evaluated.

Please Help me understand.
Is there any good way to understand these type of nested pointers?

 

[Tom St Denis]

Hello all, Below is a code snippet in C

#include<stdio.h>
int main (void)
{
static char *s[ ]  = {“black”, “white”, “yellow”, “violet”};
char **ptr[ ] = {s+3, s+2, s+1, s}, ***p;
p = ptr;
**++p;
printf(“%s\n”,*--*++p + 3);
return 0;

}

 I am getting some problem in understanding output of this problem.
Here  initially, p contains
address of first element of ptr i.e. &(s+3), then due to ++p, p is &(s
+2).
Now I can't understand how the term *--*++p in printf is evaluated.

Please Help me understand.
Is there any good way to understand these type of nested pointers?

Don't write code like that? But that being said use your order of
precedence and left-right associativity to work it out. Break it
down...

++p; // pre increment p
*++p; // pre increment p, then derefence
--*++p; // pre increment p, then derefence, then pre-decrement *++p
*--*++p; // ditto then dereference

You could write *--*++p ignoring the effects as

p[1][-1]

where p[1] points to s+1, (s+1)[-1] points to "black", and "black" + 3
resolves to "ck\0"

And indeed the output is "ck\n" as the printf does.

btw the ** on the **++p; statement doesn't do anything [useful].
Basically you're preincrementing p then dereferencing it two orders.
e.g. **++p == "white"

Tom