Appending long double literal suffix to user inputs in c++

Question

I have a class that has a long double vector:

MyClass{
    vector<long double> myvec;
    public:
        MyClass(){ //Constructor }

    // Some memeber functions that operate on the vector
};

I have overloaded the input operator an I'm taking input from a user that are then pushed into the vector. The problem that I'm having is if the user inputs a number that is out of range of double, the code should append append the long double suffix to the input with out the user having too. This is what I have tried so far:

long double input;
...
input = (long double)(input + "L");
myvec.push_back(input);

I thought of using scanf, but I'm not sure how safe that is to use when overloading the input operator.

Answer 1

Use std::stold to convert input text to long double. There is no need for a suffix; stold will do it right. The suffix is needed in source code to tell the compiler what type the text represents. When you're reading from an external source the compiler isn't involved, so you have to sort out the type yourself.