no matching function to call to “standard constructor”

Question

I get a weird response from my c++ compiler. I searched the internet but came up with nothing usefull or helpfull...

Compiler Response:

Answer 1

First, the error. Your constructor for HexFloatingPoint is not initialising the base class, FloatingPoint. Since you have defined a constructor taking two arguments, and no default constructor (containing no arguments), derived classes must initialise it using the constructor you've defined:

HexFloatingPoint::HexFloatingPoint(int sign_length,int exp_length) :
    FloatingPoint(sign_length, exp_length),  // ADD THIS
    significant_length(sign_length),
    exponent_length(exp_length)
{}

Alternatively, you might want to be able to leave the base-class members uninitialised, or initialise them to default values, in which case you'll need to provide a default constructor:

FloatingPoint() {} // or initialise the members if you want

but this probably isn't what you want to do; you probably want to initialise them properly.

Secondly, the warning. Often when you have a polymorphic base class, you'll want to delete objects of the derived through a pointer to the base class. This is only allowed if the base class declares a virtual destructor; otherwise, such deletion gives undefined behaviour. I suggest you follow the compiler's advice and add one:

virtual ~FloatingPoint() {}

Finally, once you've fixed the compiler errors then (assuming there's no more code than what you posted) you'll get linker errors due to missing definitions of FloatingPoint::set_exponent and FloatingPoint::print. This is because you've declared them virtual but not pure, and haven't implemented them. They probably want to be pure virtual like set_significant:

virtual void set_exponent(string number) = 0;
                                         ^^^