On 20-02-2012 06:53, Chad J wrote:
On 02/19/2012 09:50 PM, Alex Rønne Petersen wrote:
On 20-02-2012 03:35, Chad J wrote:
On 02/19/2012 08:00 PM, Bernard Helyer wrote:
On Monday, 20 February 2012 at 00:55:15 UTC, Alex Rønne Petersen wrote:
Hi,
http://groovy.codehaus.org/Operators#Operators-SafeNavigationOperator
What do you folks think about this? Would it be useful to have in D?
It would make navigating large object graphs with possible null values
much easier.
The traditional counter point to this is that it encourages bad/lazy
design. I don't really agree, but I don't ache for it either.
I wonder then, if this argument has been made:
I think non-nullable types would be /far/ more helpful for this.
As far as I can tell, the intend of having a "better" design would be to
find undesired nulls as close to their origination point as possible. I
really think there have to be more methodical ways to do this (ex:
non-nullable types) that don't rely on fallable human whim. After all,
if I need the ?. and don't have it, I'll just write an if-statement
instead. It'll be the same poor design, and it will be more difficult to
read too.
Or maybe... in debug mode references could be fat pointers that have
both the data ptr and a second integer that points to information about
where the last assignment took place.
struct PhatRef(T)
{
T* data;
AssignmentEntry* lastAssignment;
}
struct AssignmentEntry
{
string fileName;
size_t lineNumber;
}
Then this:
void main()
{
Foo foo;
}
Gets lowered by the compiler into this:
void main()
{
Foo foo;
foo.lastAssignment.fileName = "main.d";
foo.lastAssignment.lineNumber = 2;
}
When the null foo is referenced, the crash handler/debugger/whatever can
traverse the AssignmentEntry structure and display the debugging info.
This would save soooooo much time!
I'd personally have to object to this. My virtual machine code heavily
relies on references being plain pointers. That being said, the idea is
not bad at all! (It would be easily realizable in a managed language.)
It would be nice if D had language-integrated non-nullable types a la
Spec#.
Yeah, I figured the fat pointer would have to be configurable somehow
just because of exactly this sort of thing.
I still wonder what code that breaks with this would look like exactly.
Maybe there is a way to make it work in more possible situations.
Well, in my case, I'm emitting raw machine code that simply uses
references as pointers. I could adjust it to work with fat pointers, but
then that means I have to special-case code generation when using the D
runtime's GC versus any of the built-in GCs, which would be annoying. :/
--
- Alex
