references and function calls

[Frits van Bommel]

Neal Becker wrote:
> I've been reading the D specification.  A couple of questions:
> 1. Do I understand correctly that D has no reference type declarations
> (there is no e.b., int& x;)?

Yes. (but see below for parameters)

> 2. Reading the section on functions, unfortunately I don't think it is clear
> on how arguments are passed.  Do I understand correctly that argument
> passing is like java: POD are passed by value but other objects (class
> instances) are passed by reference?

By default:
Everything but objects and arrays are passed by value.
Objects are passed by reference (or perhaps more correctly: the 
reference to the data is passed by value).
Arrays are similar: The data in the array is passed by reference, but 
the reference to it is passed by value. In the case of dynamic arrays, 
the reference also contains the length so this makes a difference.

But this behavior can be changed by specifying 'inout' or 'out'.
Both of those tell the compiler the parameter is to be passed by reference.
In the case of objects and arrays, the reference is passed by reference. 
That means you can change the object or data being referred to and/or 
the length of dynamic arrays.
The difference between 'out' and 'inout' is that 'out' 
default-initializes the parameter at the start of the function, so you 
can't pass in data that way.

You can also specify 'in', but that specifies the default behavior.

There's also 'lazy', which turns the expression passed into a delegate 
that evaluates the expression. The expression is only evaluated if the 
delegate is ever called, but it's re-evaluated every time it's called.