Programming Forums > Application Development > C++

sayu · Nov 12th, 2006, 5:23 AM

hello
can anybody say the code required to convert a string to integer datatype

that is get a number as a string type and convert it integer

ex
char num[10];
cout<<"Enter a number: ";
cin>>num;

// convert num to int datatype so that arithmetic calcs is possible

Klarre · Nov 12th, 2006, 7:04 AM

In this case you can set your num variable to an int, cause you are using streams. Otherwise you should google for the atoi(...) function.

/Klarre

grumpy · Nov 12th, 2006, 7:04 AM

Firstly, read the sticky post, always at the top of the C++ forum, entitled "How to post a question". It will give you useful tips on how to ask questions in a way that increases your chance of getting a useful response. One part of that is learning how to use [code[bf][/bf]] tags to present code in a more readable form.

If all you want to do is read an int from a standard stream, do this;

(Toggle Plain Text)

#include <iostream>

int main()
{
    int num;
    std::cout << "Enter a number : ";
    std::cin >> num;
}

This works because the standard stream types support input and output of basic types.

If you want to read it as a string first (which is valid, as it means you can do extra error checking) one approach is this;

(Toggle Plain Text)

#include <iostream>
#include <string>
#include <sstream>

int main()
{
    char buffer[10];
    std::cout << "Enter a number : ";
    std::cin.getline(buffer, 10);           // note that this does not overflow buffer
    
    std::string temp(buffer);              //  store copy of buffer in a string
    std::istringstream mystream(temp);  // create a stream to read from temp
    int value;
    mystream >> value;
}

kruptof · Nov 12th, 2006, 11:18 AM

i think there is a function which will allow you to do this ...i am not quite sure but i think it is called atoi() and needs the inclusion of the stdlib header file...like i said not quite sure...?

Game_Ender · Nov 12th, 2006, 3:03 PM

If you are to use C functions atoi is not the best function for str->num conversion. You should use: strtol because it allows better error checking.

crawforddavid2006 · Nov 12th, 2006, 10:26 PM

ok this is no help but DID YOU EVEN THINK OF SEARCHING THE FORUMS?

titaniumdecoy · Nov 12th, 2006, 10:45 PM

Why doesn't someone compile a list of answers to all the basic C++ questions like this one that get asked millions of times and post it as a sticky in this forum?

Mocker · Nov 13th, 2006, 1:35 AM

Quote:

Originally Posted by titaniumdecoy

Why doesn't someone compile a list of answers to all the basic C++ questions like this one that get asked millions of times and post it as a sticky in this forum?

Thanks for volunteering

grumpy · Nov 13th, 2006, 3:12 AM

Quote:

Originally Posted by titaniumdecoy

Why doesn't someone compile a list of answers to all the basic C++ questions like this one that get asked millions of times and post it as a sticky in this forum?

If you wish to volunteer, go ahead.

In my experience, the majority of such questions come from newbies who have not bothered to read forum guidelines or any existing FAQs. So, after preparing a FAQ, you would probably just be changing the focus of your frustration towards "why don't they read the FAQ?".

mrynit · Nov 13th, 2006, 4:16 AM

or you could make a chat bot that would parse every thing and come up with the best answers.

Nov 12th, 2006, 5:23 AM	#1
sayu Newbie Join Date: Nov 2006 Posts: 10 Rep Power: 0	convert to int hello can anybody say the code required to convert a string to integer datatype that is get a number as a string type and convert it integer ex char num[10]; cout<<"Enter a number: "; cin>>num; // convert num to int datatype so that arithmetic calcs is possible

Nov 12th, 2006, 7:04 AM	#2
Klarre Game engine designer Join Date: May 2005 Location: Sweden Posts: 314 Rep Power: 4	In this case you can set your num variable to an int, cause you are using streams. Otherwise you should google for the atoi(...) function. /Klarre __________________ http://www.klarre.se

Nov 12th, 2006, 7:04 AM	#3
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,260 Rep Power: 5	Firstly, read the sticky post, always at the top of the C++ forum, entitled "How to post a question". It will give you useful tips on how to ask questions in a way that increases your chance of getting a useful response. One part of that is learning how to use [code[bf][/bf]] tags to present code in a more readable form. If all you want to do is read an int from a standard stream, do this; (Toggle Plain Text) #include <iostream> int main() { int num; std::cout << "Enter a number : "; std::cin >> num; } #include <iostream> int main() { int num; std::cout << "Enter a number : "; std::cin >> num; } This works because the standard stream types support input and output of basic types. If you want to read it as a string first (which is valid, as it means you can do extra error checking) one approach is this; (Toggle Plain Text) #include <iostream> #include <string> #include <sstream> int main() { char buffer[10]; std::cout << "Enter a number : "; std::cin.getline(buffer, 10); // note that this does not overflow buffer std::string temp(buffer); // store copy of buffer in a string std::istringstream mystream(temp); // create a stream to read from temp int value; mystream >> value; } #include <iostream> #include <string> #include <sstream> int main() { char buffer[10]; std::cout << "Enter a number : "; std::cin.getline(buffer, 10); // note that this does not overflow buffer std::string temp(buffer); // store copy of buffer in a string std::istringstream mystream(temp); // create a stream to read from temp int value; mystream >> value; }

Nov 13th, 2006, 4:16 AM	#10
mrynit Hobbyist Programmer Join Date: Mar 2006 Location: WA, USA Posts: 343 Rep Power: 3	or you could make a chat bot that would parse every thing and come up with the best answers. __________________ i dont know much about programming but i try to help

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Nov 12th, 2006, 3:03 PM	#5
Game_Ender Professional Programmer Join Date: May 2006 Location: Maryland, USA Posts: 306 Rep Power: 3	If you are to use C functions atoi is not the best function for str->num conversion. You should use: strtol because it allows better error checking.

Nov 12th, 2006, 10:45 PM	#7
titaniumdecoy Expert Programmer Join Date: Nov 2005 Posts: 934 Rep Power: 4	Why doesn't someone compile a list of answers to all the basic C++ questions like this one that get asked millions of times and post it as a sticky in this forum?

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Programming Forums > Application Development > C++

convert to int