Why should default parameters be added last in C++ functions?

Question

Why should default parameters be added last in C++ functions?

Answer 1

If you define the following function:

void foo( int a, int b = 0, int c );

How would you call the function and supply a value for a and c, but leave b as the default?

foo( 10, ??, 5 );

Unlike some other languages (eg, Python), function arguments in C/C++ can not be qualified by name, like the following:

foo( a = 10, c = 5 );

If that were possible, then the default arguments could be anywhere in the list.