C++ Default values in functions? -

how default values in functions work? question pertains example:

int func(int number, std::string name = "none", int anothernumber);  ..  int func(int number, std::string name, int anothernumber){     ... }  func(1, 2); ^error, name null yet we've defined default value? 

the compiler gives error complaining argument null , should not be. yet i've defined default value it.

why this?

if default parameter @ position k supplied, parameters in positions k+1 end must supplied well. c++ allows omit parameters in end positions, because otherwise has no way of matching parameter expressions formal parameters.

consider example:

int func(int a, int b=2, int c, int d=4); ... foo(10, 20, 30); 

this call ambiguous, because supplies 3 parameters out of four. if declaration above allowed, c++ have choice of calling

func(10, 20, 30, 4); 

or

func(10, 2, 30, 40); 

with defaulted parameters @ end , rule parameters matched position, there no such ambiguity:

int func(int a, int b, int c=2, int d=4); ... foo(10, 20, 30); // means foo(10, 20, 30, 4);