Question

How do you read in a double from a file in C++?

For ints I know you can use the getline() and then atoi, but I am not finding an array to double function. What is available for reading in doubles, or converting a char array to a double?

Answer 1

You can use stream extraction:

std::ifstream ifs(...);
double d;
ifs >> d;

This work provided that other then whitespace, the next data in the stream should be a double in textual representation.

After the extraction, you can check the state of the stream to see if there were errors:

ifs >> d;
if (!ifs)
{
    // the double extraction failed
}