• brad beveridge (15/15) Nov 30 2003 Hi there, I've just started playing with D & am wondering about the
• Russ Lewis (13/27) Nov 30 2003 Although I see your point, I think that the current implementation makes...

brad beveridge <brad nospam.com> writes:

Hi there, I've just started playing with D & am wondering about the 
in/out/inout parameters.
Firstly - the documentation example of
	void foo(out int bar)
	{
	}

	int bar = 3;
	foo(bar);
	// bar is now 0
doesn't work :)  bar is still 3.
so for "out" bar isn't being initialised to 0.

Next, because objects are passed by reference, is there anyway to make 
them "const"?  Or is that an assertation using the design by contract?

Cheers
Brad

Russ Lewis <spamhole-2001-07-16 deming-os.org> writes:

brad beveridge wrote:
 Hi there, I've just started playing with D & am wondering about the 
 in/out/inout parameters.
 Firstly - the documentation example of
     void foo(out int bar)
     {
     }
 
     int bar = 3;
     foo(bar);
     // bar is now 0
 doesn't work :)  bar is still 3.
 so for "out" bar isn't being initialised to 0.

Although I see your point, I think that the current implementation makes 
sense.  If the function does nothing, then really nothing should be 
done.  I could see how people might argue otherwise, but it's really a 
coin toss what to do, IMHO.

 Next, because objects are passed by reference, is there anyway to make 
 them "const"?  Or is that an assertation using the design by contract?

Walter has stated that he won't support const in function parameters 
because they are too problematic.  They force a lot of weird rules on 
the language, apparently.  (I don't remember his posts in enough detail 
to remember exactly what scenarios are problematic.)

'const', in D, is used only for global constants.  It is a clue to the 
compiler that these variables are good ones to locate in the read-only 
section of the linked executable.  (Thus, an attempt to write to them 
should cause a segmentation fault.)