Code:
char again[2];
Before strcmp i also tried: if (again == "y")
char literals are denoted with single quotes:
if(again=='y')
while string literals are denoted with double quotes:
"some text"
A string literal can be used to initialize a char array:
char again[] = "y";
However, that is a two step process. If I've got this right, what happens is that when the compiler sees a string literal, it first tacks on a '\0' to the end of the string literal:
y\0
and stores it in memory somewhere. Then, the address is assigned to the variable 'again'.
So, in actuality, a char array name is a pointer to a string in memory(see below as to why that is difficult to prove). Therefore, when you do this:
if (again == "y")
you are comparing an address stored in the pointer 'again' to "y". But, an address looks something like this: 006BFDF4, so they will never be equal.
To compare c-strings, you have to use strcmp() in <cstring>. strcmp() returns 0 if the cstrings are equal:
Code:
char again[] = "y";
if(strcmp(again, "y")==0)
{
cout<<"they are the same"<<endl;
}
else
{
cout<<"not the same"<<endl;
}
Originally Posted by
AH_Tze
You can't use cout on a c-string.
In fact, cout<< is specifically tailored to handle c-strings. c-string variables are pointers to the strings, and normally when you cout<< a pointer variable, you get an address:
Code:
int num = 10;
int* p = #
cout<<p<<endl; //006BFDF4
However, with c-strings the <<operator is programmed to automatically convert the address to the value at that address, and display the string:
Code:
char text[] = "some text";
cout<<text<<endl; //some text
That is why it is hard to know that a char array name is actually a pointer.
Where you may have gotten confused is that there is a distinction between an "array-of-chars" and a c-string. The terms char arrays and c-strings are sometimes used interchangeably, but then you have to have a term to identify another entity, which I'm calling an "array-of-chars". An "array-of-chars" is different from a c-string/char array. The defining aspect of a c-string/char array is that the array ends with a '\0' character. That '\0' character enables the <cstring> functions and cout<< to know when the end of the array has been reached, and to stop. With an array-of-chars, there is no '\0' character at the end of the array, so the <cstring> functions and cout<< will run past the end of the array and go out of bounds, spewing out all kinds of junk characters. Here is an example:
char my_array[] = {'a', 'b', 'c'};
cout<<my_array<<endl; //abc#@$
If you try that, it will display abc, but then you will also get a bunch of junk after that, as the <<operator runs past the end of the array. There is no '\0' char to signal the end of the array, so the <<operator keeps going.
To ouput an array-of-chars, you have to use a for-loop and output each char one at a time. You also need to know the size of the array, so you can tell the for-loop when to stop, and prevent it from going out of bounds:
Code:
char my_array[] = {'a', 'b', 'c'};
for(int i=0; i<3; i++)
{
cout<<my_array[i];
}
cout<<endl;
Presumably, the <<operator is programmed to ouput a c-string in much the same way, it just has to check for the '\0' char so it doesn't go out of bounds:
Code:
char my_array[] = "abc";
int i = 0;
while(my_array[i] != '\0')
{
cout<<my_array[i];
i++;
}
Similarly, the <cstring> functions are all pretty simple functions that just loop through a char array until they come across a '\0', and then they end.
