Thread: help me find out why it is like this

Link.

Actually, I didn't know myself string had this method. I have always used += for appending.

Code:

std::string numericString;
for(int i = 0; i < 5; i++){
    numericString += '1';
}

Originally Posted by laserlight

No, since it is an idiom for null terminated strings, which std::string is (generally) not. A simple index based for loop will suffice:

Code:

for (std::string::size_type i = 0, len = str.length(); i != len; ++i)
{
    // Access str[i] here.
}

You could also use string iterators with a generic algorithm like say, std::copy_if (or at the moment: std::remove_copy_if since std::copy_if would only be around in C++0x).

whats this ? and why is it there ? if we use using namespace std; do we still need to include "std::string::size_type" ?

Originally Posted by Masterx

whats this ? and why is it there ?

What do you mean? I merely provided an example of how to use an index based for loop to iterate over the characters of a string. You would need to combine this with std::string's push_back(), or whatever method you wish to use to append to the destination string.

Originally Posted by Masterx

if we use using namespace str; do we still need to include "std::string::size_type" ?

You would not need to fully qualify std::string::size_type, so you could write it as string::size_type. std::string::size_type is the index type of std::string.

Originally Posted by laserlight

What do you mean? I merely provided an example of how to use an index based for loop to iterate over the characters of a string. You would need to combine this with std::string's push_back(), or whatever method you wish to use to append to the destination string.


You would not need to fully qualify std::string::size_type, so you could write it as string::size_type. std::string::size_type is the index type of std::string.

tanx alot. im going to test these . i'll let you know , if i was successful.

Originally Posted by Masterx

i cant use "atoi() with string ! what should i do now ?atol() ? does it make it?

You actually "solved" this problem in your original code by using the c_str() member function of std::string.

Originally Posted by laserlight

You actually "solved" this problem in your original code by using the c_str() member function of std::string.

yeah , tanx for saying that . but my intention of asking such a question was that , i just want to know if there is any equivalent for string in C++! ? is there ? !

by the way , how could you guys understand that ptr was not allocated ! ? by experience or just its the knowledge of C++ that i can find in books/.?

Stringstreams.

Code:

string s("12345");
int n;
stringstream ss(s);
ss >> n;

Originally Posted by anon

Stringstreams.

Code:

string s("12345");
int n;
stringstream ss(s);
ss >> n;

many tanx. now i got it .the use of stringstream that Elysia and laiserlight used to tell me multiple times and i couldnt understand how it works! lol)

Originally Posted by tabstop

Generally it's called "reading the code". You start at the top and you go to the bottom (going around and around in loops, naturally). You used ptr, but you never created any memory for it to point to.

many tanx for the info dear tabstop.