atof(string)

[allexander]

Hello !

I need to convert a string like

string number = "1235646.56 78"

to any floating point number x
(double x or float x)

I have used earlier the function atof()
but now I it's looking so,
that I need some array
of chars like

char cnumber[]

to use it as an argument for atof.

How can I convert number into x reliably ?

instructions sequence like :

double x;
string number = "1235646.56 78";

x=atof(number);

is wrong. the compiler answers :

cannot convert `std::string' to `const char*' for argument `1' to `double atof(const char*)'

what's to do ?

[JosAH]

double x;
string number =  "1235646.5678";
 
x=atof(number);

is wrong. the compiler answers :

cannot convert `std::string' to `const char*' for argument `1' to `double atof(const char*)'

what's to do ?

You have to do it yourself. The string class has a const char* c_str() method
which gives you the 'C' representation of that string, i.e. a char array zero
terminated.

kind regards,

Jos

[weaknessforcats]

Avoid atof(). It is a legacy C function. In C++ use a stringstream:

string number = "1235646.5678";
stringstream ss;
ss << number;
double result;
ss >> result;
 

By using a stringstream you can use your << and >> operators to put other things in the stringstream.

You will need to include <sstream>