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#1
May 22nd, 2003, 02:54 PM
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What's the meaning of: int const *pt
Is it equivalent to
const int *pt or int *const pt  What's the systematic way to determine the meaning of such expressions (with const qualifier)? Thanks a lot.
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#2
May 22nd, 2003, 03:28 PM
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Hey a C++ question that I can answer!!! I just read about doing this in my N00b book so I may still be wrong.
Anyway, if I remeber correctly const int *pt can only point to a const integer, while int *const pt is a pointer that only points to one place and can not be changed. I think that is right  .
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#4
May 22nd, 2003, 04:07 PM
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int const *p is equivalent to const int *p (at least according to my g++ 2.95 compiler). There is a difference between const int *p and int * const p though.
const int *pi * Can be pointed at multiple variables. * Cannot be used to assign a new value to a variable via indirection. int *const ip * Can only be pointed to a single variable (done at initialization) * Can be used to assign a new value to a variable via indirection. const int * const pip (Yes, it is possible to declare a variable of this type too.) * Can only be pointed to a single variable (done at initialization) * Cannot be used to assign a new value via indirection To illustrate the differences: Code:
#include <iostream>
using namespace std;
int main(void) {
int x = 1;
int y = 2;
const int *pi;
pi = &x;
pi = &y; // Can be pointed to another variable
*pi = 23; // <----- NOT ALLOWED
cout << *pi << endl; // <--- Value can be accessed
int * const ip = &x;
*ip = 7; // <----- Can assign a value via indirection
ip = &y; // <----- NOT ALLOWED
cout << *ip << endl; // <---- Value can be accessed
const int * const pip = &y;
*pip = 42; // <------ NOT ALLOWED
pip = &x; // <------ NOT ALLOWED
cout << *pip << endl;
return 0;
}
Hope this helps 
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