xo-gc xo-object2 xo-facet: builds w/ ISequence,Dlist

xo-object2/src/object2/DList.cpp

@@ -0,0 +1,54 @@
+/** @file DList.cpp
+ *
+ *  @author Roland Conybeare, Dec 2025
+ **/
+
+#include "DList.hpp"
+#include <xo/indentlog/print/tag.hpp>
+
+namespace xo {
+    namespace scm {
+        auto
+        DList::size() const noexcept -> size_type
+        {
+            const DList * l = this;
+
+            size_type z = 0;
+
+            while (l) {
+                ++z;
+                l = l->rest_;
+            }
+
+            return z;
+        }
+
+        auto
+        DList::at(size_type index) const -> obj<AGCObject>
+        {
+            size_type ix = index;
+            const DList * l = this;
+
+            while (l->rest_ && (ix > 0)) {
+                --ix;
+                l = l->rest_;
+            }
+
+            if (ix > 0) {
+                assert(l == nullptr);
+
+                throw std::runtime_error
+                    (tostr("DList::at: out-of-range index where [0..z) expected",
+                           xtag("index", index),
+                           xtag("z", this->size())));
+            }
+
+            assert(l);
+
+            return l->head_;
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DList.cpp */