On 26/04/12 12:11, Timon Gehr wrote:
On 04/26/2012 11:46 AM, Don Clugston wrote:
On 26/04/12 11:28, Timon Gehr wrote:
On 04/26/2012 10:51 AM, Don Clugston wrote:
On 26/04/12 05:44, Walter Bright wrote:
A subtle but nasty problem - are default arguments part of the
type, or
part of the declaration?
See http://d.puremagic.com/issues/show_bug.cgi?id=3866
Currently, they are both, which leads to the nasty behavior in the bug
report.
The problem centers around name mangling. If two types mangle the
same,
then they are the same type. But default arguments are not part of the
mangled string. Hence the schizophrenic behavior.
But if we make default arguments solely a part of the function
declaration, then function pointers (and delegates) cannot have
default
arguments. (And maybe this isn't a bad thing?)
I think it is a mistake to allow default arguments in function pointers
and delegates (it's OK for delegate literals, there you have the
declaration).
The parenthesised part is in conflict with your other statement.
No it doesn't. A default argument is a delegate literal is part of the
declaration, not part of the type.
If types cannot specify default arguments, then those will be thrown
away right away, because what is later called is based on the type of
the delegate and not on the implicit function declaration that has its
address taken. What is the point of allowing it if it cannot be used?
Fair point. It could be used in the case where it is called at the point
of declaration (I do that a fair bit), but it's pretty much useless
because it is clearer code to put the default parameter in the call.
int m = (int a, int b = 3){ return a+b;}(7);
Point conceded. So default arguments should be disallowed in delegate
literals as well.
