strings again
Why iszero1 == false as iszero2 == true and iszero3 == true too?Code:char *number = "0"; bool iszero1 = ("0" == number); bool iszero2 = (0x30 == number[0]); bool iszero3 = (NULL == number[1]);
"0" is an array with two char (1 byte each) values, the first is 48 (0x30) and the second is 0 (NULL), isn't it?
Please excuse my poor english...
The first comparison is illegal because for char arrays you need to use strcmp. The other two compare single characters.
Actually I'd try to dereference the pointer rather than try to compare an address to a string literal, but I still don't see how it would work. You need strcmp.
Last edited by Troll_King; 10-14-2001 at 09:52 AM.
If you dereference string pointer, you get single char value, don't you? Because char *text is pointer to first item in a string array. Nevermind, strcmp should do what I need. Thanx.
Please excuse my poor english...
OK, the reason this happens is because each string literal is added to the data section, and two strings that are the same are both added.Originally posted by larry
Why iszero1 == false as iszero2 == true and iszero3 == true too?Code:char *number = "0"; bool iszero1 = ("0" == number); bool iszero2 = (0x30 == number[0]); bool iszero3 = (NULL == number[1]);
"0" is an array with two char (1 byte each) values, the first is 48 (0x30) and the second is 0 (NULL), isn't it?
This instruction:
bool iszero1 = ("0" == number);
means "does number point at the address of this literal string?", NOT "does the string pointed at by number the same as this literal string"
This code is analogous, in what it is doing, to this:
int * x1, x2;
x1 = new int;
x2 = new int;
*x1 = *x2 = 7;
bool iszero1 = (x1 == x2); // this is false, because, although they contain the same value, they do not point to the same address!
strcmp is the string equivalent of doing this:
bool iszero2 = (*x1 == *x2);
