Refactor Support.

include/Support/Compare.h

@@ -0,0 +1,42 @@
+#pragma once
+
+#include "Struct.h"
+
+namespace clice::support {
+
+constexpr auto equal(const auto& lhs, const auto& rhs) {
+    if constexpr(requires { lhs == rhs; }) {
+        return (lhs == rhs);
+    } else {
+        return support::foreach(lhs, rhs, [](const auto& lhs, const auto& rhs) {
+            return support::equal(lhs, rhs);
+        });
+    }
+}
+
+/// Compare lhs and rhs according to the dictionary order of their members.
+constexpr auto less(const auto& lhs, const auto& rhs) {
+    if constexpr(requires { lhs < rhs; }) {
+        return (lhs < rhs);
+    } else {
+        bool result = false;
+        support::foreach(lhs, rhs, [&result](const auto& lhs, const auto& rhs) {
+            /// if lhs less than rhs, abort the iteration and return true.
+            if(support::less(lhs, rhs)) {
+                result = true;
+                return false;
+            }
+
+            /// if lhs equal to rhs, continue to next member.
+            if(support::equal(lhs, rhs)) {
+                return true;
+            }
+
+            /// if lhs greater than rhs, abort the iteration and return false.
+            return false;
+        });
+        return result;
+    }
+}
+
+}  // namespace clice::support