C++ String: How to convert a string into a numeric type?

[sandodo]

In addition to FAQ:

Please note that using function sccanf() to convert string into f with float type,

sscanf(str_float, "%f", &f);

The result may not be what you want.
refer to the example of FAQ:

printf("f is now = %f\n", f);

You will find the out is: f is now = 333.299988

The myth here is sccanf actually convert str_float into double type. if you cast it back to float, there will be some differences, because the way floating point is represented. See this FAQ for more.