need help with casting

[manontheedge]

I'm trying to cast a char* to a long ... but I keep getting compiler errors no matter how I do it ... here's the small sample I've been messing with. I just have console input, where I'll enter an integer ...

 
char x[15];    // or char* x;  -- I'd like to be able to do both
long longResult;
 
// these both produce a jumbled result
longResult = (long)x;
 
longResult = reinterpret_cast<int> (x);
 
// this one gives the error -- cannot convert from 'char *' to 'long
longResult = static_cast<long> (x);                
 
 

... i apparantly have no idea what I'm doing, so I'd be grateful for any help.

[Banfa]

Do not use a C style cast in C++ because you can not be sure what underlying cast the cmpiler will have chosen to do. It is only there for support of C code.

The reinterpret_cast is the one you want for this, this tells the compiler to interpreate the bits of one type as another type, not performing any sort of conversion.

The static_cast converts 1 type to another, since there are no pointer to integer converstion the compiler produces an error.

The output of the reinterpret_cast is the address of the string as a number, you describe this as a jumbled result. This leads me to think that may be you are trying to convert a string of digits to a number, i.e. get the value the string "1234" as a long type.

You could do this like this

#include <iostream>
#include <sstream>
 
using namespace std;
 
int main()
{
    char data [] = "1234";
    long result;
 
    stringstream converter(data);
 
    converter >> result;
 
    cout << result << endl;
 
    return 0;
}

[manontheedge]

Banfa,

thank you for the explanations, and for that sample code. That's exactly what I'm trying to do. I'm sending multiple data accross a network, and I chose to send them all as strings, but I need to pick out numbers in some of them.

Your code has some things I've never seen, so I'll have to look that up. Anyway, thank you very much for your help ... saved me a lot of time and stress.