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Jul 19th, 2007

Conversion from Char* to int ?

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Hi All,

I want to convert char * to int.

Plz help me out.

Thanks in advance.

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RohitSahni

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Jul 19th, 2007

Re: Conversion from Char* to int ?

What exactly do you mean?
Do you
a) want to convert an array of ASCII characters into an int:

C++ Syntax (Toggle Plain Text)
char *numstr = "1234";
int val = atoi(numstr);    // val now = 1234
char *numstr = "1234";
int val = atoi(numstr);    // val now = 1234

b) convert the pointer to an int:

C++ Syntax (Toggle Plain Text)
char *xyz;   // given contents somewhere
int addr = (int)xyz;   // addr now = the char pointer
char *xyz;   // given contents somewhere
int addr = (int)xyz;   // addr now = the char pointer

dougy83

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Jul 19th, 2007

Re: Conversion from Char* to int ?

Thanks a lot for your Rply..i will be using atoi().
And it worked for me.

RohitSahni

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Jul 19th, 2007

Re: Conversion from Char* to int ?

Don't use atoi() - here's how to do it in C++

CPP Syntax (Toggle Plain Text)
#include <sstream>
#include <iostream>
 
int main()
{
    const char* foo("1234");
    std::stringstream ss(foo);
    int i;
    if( ss >> i )
        std::cout << "i is: " << i ;
    else
        std::cout << "error";
}
#include <sstream>
#include <iostream>

int main()
{
    const char* foo("1234");
    std::stringstream ss(foo);
    int i;
    if( ss >> i )
        std::cout << "i is: " << i ;
    else
        std::cout << "error";
}

The reason for using stringstreams is that your conversion will fail if the string contains anything which can't be converted to an int - which, if you're dealing with user input, is a real problem. if you use a stringstream, you can detect the error, without it messing up the rest of the program.

Bench

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Jul 19th, 2007

Re: Conversion from Char* to int ?

Quote ...

Don't use atoi()

Why?

Hamrick

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Jul 19th, 2007

Re: Conversion from Char* to int ?

I suppose I should add that atoi() has no reliable way of handling any errors that might be thrown up when your conversion fails. This is where stringstreams provide a far more robust solution, that you can test for failure before using the retrieved value.

Last edited by Bench; Jul 19th, 2007 at 9:59 am.

Bench

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Jul 19th, 2007

Re: Conversion from Char* to int ?

> Why?
Answer.

~s.o.s~

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