I need to user Red-Black trees with non-default sorting.
Here is a minimal example
---- >8
import std.container;
struct CC {
int a;
int b; }
bool less(const ref CC lhs, const ref CC rhs) {
if (lhs.a != rhs.a)
return lhs.a < rhs.a;
else
return lhs.b < rhs.b; }
void main() {
auto t = new RedBlackTree!(CC, "a.a != b.a ? a.a < b.a : a.b
< b.b"); }
8< ----
It works, but I would like to pass the function "less" as
comparison operator since in my real problem the comparison is a
more complex.
I tried this ways:
auto t = new RedBlackTree!(CC, less);
auto t = new RedBlackTree!(CC, CC);
auto t = new RedBlackTree!(CC, &less);
auto t = new RedBlackTree!(CC, "less(a,b)");
auto t = new RedBlackTree!(CC, "what the hell!? just call
less! Is it too much to ask?");
None of them works, I am stuck. The documentation states:
(quote from:
http://dlang.org/phobos/std_container.html#.RedBlackTree )
"""
To use a different comparison than "a < b", pass a different
operator string that can be used by std.functional.binaryFun, or
pass in a function, delegate, functor, or any type where less(a,
b) results in a bool value.
"""
What is wrong? How I am supposed to pass less address to do the
comparison?
Thanks