On Tuesday, 24 July 2012 at 05:30:49 UTC, Ali Çehreli wrote:
The options that I can think of:
- Return a struct (or a class) where one of the members is not
filled-in
- Similarly, return a tuple
This is awkward, and doesn't look good for performance.
- Use an out parameter, which can have a default lvalue:
int g_default_param;
void foo(ref int i = g_default_param)
{
if (&i == &g_param) {
// The caller is not interested in 'i'
} else {
// The caller wants 'i'
i = 42;
}
}
void main()
{
foo();
int i;
foo(i);
assert(i == 42);
}
This is not working inside a class. I'm not sure what default
value I should put when I don't know the type entered:
class a (T) {
T dummy = T.init;
bool foo(int a, out T optional = dummy)
{
return true;
}
}
void main () {
auto c = new a!uint();
c.foo(5);
}
I get the following error:
Error: need 'this' to access member dummy
