Quick question (beginner)

The following code fragment:

Code:

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#include <iostream>
#include <string>

using namespace std;

int main()
{
char input[300], *p, *q[300], **r = q;

 cin.getline(input, 300);

 for (p = input; *p; p++)
  switch (tolower(*p)) {
  case 'e':
    *r++ = p;
    break;
  case '.':
  case '\'':
  case ' ':
    *p = '\0';
    break; }
 *r = 0;

 for (r = q; *r; r++)
  cout << *r << " ";

 cout << endl;
}

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was given as an example exam for my introduction programming course. What i don't understand is the use of the *p and *r as the middle argument in the for loops. I've only used inequalities for that location, so i have no idea what that means for pointers. Any help is appreciated.

You need to indent the code properly to see more clearly what it is doing. Also, just post the code as-is within the code tags; don't try to apply any formatting as the forum software will apply it for you.

Quote:

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Originally Posted by laserlight

You need to indent the code properly to see more clearly what it is doing. Also, just post the code as-is within the code tags; don't try to apply any formatting as the forum software will apply it for you.

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ok, done.

Quote:

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Originally Posted by JMaxwell

What i don't understand is the use of the *p and *r as the middle argument in the for loops.

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*p and *r dereference the pointers thus getting the value of a character.
C interprets any integral value 0 as false. Therfore the loop ends when the '\0' character is found and that is the end of string marker.
Kurt

Quote:

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Originally Posted by ZuK

*p and *r dereference the pointers thus getting the value of a character.
C interprets any integral value 0 as false. Therfore the loop ends when the '\0' character is found and that is the end of string marker.
Kurt

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Thanks, i didn't realize that the null character was taken as false when used as a boolean expression.
One last question though:
I've seen *r=*p and r=p and understand the difference but what does the expression **r=q mean in this case?

Quote:

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Originally Posted by JMaxwell

what does the expression **r=q mean in this case?

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This is an initialisation and initializes the pointer to pointer of char r with the value q and that is an array of 300 pointers to char and is compatible with a pointer to pointer to char.
Kurt