On Thu, 18 Apr 2013 11:26:22 -0400, Maxim Fomin <ma...@maxim-fomin.ru>
wrote:
On Thursday, 18 April 2013 at 13:37:45 UTC, ixid wrote:
I know this will not be changed, I just want to understand why it is as
it is.
My naive thought is that consistency is the best scheme and that
everything should have been passed by value or everything by reference
unless the user specifies otherwise.
Classifying types as passed by value and passed by reference
types is a little bit confusing sometimes)
In D, like in C, everything is passed by value (unless parameter
is specified as ref, also note that in C passing by reference is
a simulation done by pointers). Confusion comes when there is
data which points to another data. Learning how data types are
constructed is better approach than classifying their categories.
The former sometimes can explain what the latter cannot:
http://dpaste.dzfl.pl/7744d11e
AA array behaves like a reference type, but when it is reset to
null, it acts like a value type. Contradiction is caused by
complex data structes with mixed structs and pointers in AA
implementation.
AA's are not passed by reference, they ARE a reference. That reference is
ALWAYS passed by value, unless ref is used.
The problem with AA's is that the special reference null mutates upon
first addition to the AA, and never changes afterwards, unless
reassigned. It is always passed by value.
In fact, if default construction allowed allocating the initial reference
(or null wasn't treated specially), we wouldn't have that problem.
-Steve
