xo-interpreter2 stack: modularize nth() primitive setup/install

src/procedure2/ObjectPrimitives.cpp

@@ -0,0 +1,45 @@
+/** @file ObjectPrimitives.cpp
+ *
+ *  @author Roland Conybeare, Mar 2026
+ **/
+
+#include "ObjectPrimitives.hpp"
+#include "Primitive_gco_2_gco_gco.hpp"
+#include <xo/object2/Sequence.hpp>
+#include <xo/object2/Integer.hpp>
+
+namespace xo {
+    using xo::scm::ASequence;
+    using xo::mm::AAllocator;
+    using xo::mm::AGCObject;
+
+    namespace scm {
+
+        // TODO: seq_gc -> obj<ASequence>
+        //       n_gco -> obj<AGCObject,DInteger>
+        //
+        obj<AGCObject>
+        xfer_nth(obj<ARuntimeContext> rcx,
+                 obj<AGCObject> seq_gco,
+                 obj<AGCObject> n_gco)
+        {
+            scope log(XO_DEBUG(true));
+
+            (void)rcx;
+
+            obj<ASequence> seq = seq_gco.to_facet<ASequence>();
+            auto n = obj<AGCObject,DInteger>::from(n_gco);
+
+            return seq.at(n->value());
+        }
+
+        DPrimitive_gco_2_gco_gco *
+        ObjectPrimitives::make_nth_pm(obj<AAllocator> mm)
+        {
+            return DPrimitive_gco_2_gco_gco::_make(mm, "nth", &xfer_nth);
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end ObjectPrimitives.cpp */