Using in as a parameter qualifier

[Shriramana Sharma]

Hello people.

I have a pair type defined as :

struct pair {
  double x,y ;
  this () {}
  this (double x, double y) { this.x = x ; this.y = y ; }
}

Consider a function that operates on a pair:

double abs2 ( pair a ) { return a.x * a.x + a.y * a.y ; }

In C++ the function signature would be: double abs2 ( const pair & a )

So I thought const ref pair a would be appropriate in D -- is that right?

How about the "in" qualifier? Does it only replace C++'s const in this
case or does it also guarantee that the object will not be copied
(&/ref) ?

Also: does D not require member initializer lists like in C++? In C++
I would write the this(double,double) above as: pair(double x, double
y):x(x),y(y){} -- since that language is supposed to guarantee that
once we enter the { of the constructor, all sub-objects are
initialized.

Thanks!

-- 
Shriramana Sharma ஶ்ரீரமணஶர்மா श्रीरमणशर्मा