On Thursday, 3 April 2014 at 07:16:53 UTC, simendsjo wrote:
On 04/03/2014 09:03 AM, dnspies wrote:
If two dynamic arrays point to the same place in memory, is it
fast to
compare them for equality? or does every element still have to
be compared?
Equals will first check for memory location.
This is from the runtime:
bool opEquals(Object lhs, Object rhs)
{
// If aliased to the same object or both null => equal
if (lhs is rhs) return true;
// If either is null => non-equal
if (lhs is null || rhs is null) return false;
// If same exact type => one call to method opEquals
if (typeid(lhs) is typeid(rhs) ||
typeid(lhs).opEquals(typeid(rhs)))
return lhs.opEquals(rhs);
// General case => symmetric calls to method opEquals
return lhs.opEquals(rhs) && rhs.opEquals(lhs);
}
But this only applies to objects with a class type. A dynamic
array isn't an object with a class type, it's a builtin type.
Does it use this opEquals? Can a dynamic array even be cast to
an Object? I don't see that "lhs is rhs" will return true since
the array startptr-length pairs may still occupy different places
in memory even if the contents of those arrays occupy the same
place.
