From 0d23fa97b8d3a8661a9d6829ea14a310e02250e3 Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Mon, 26 Jan 2026 15:45:40 -0500
Subject: [PATCH] xo-expression2: + DApplyExpr::make

---
 xo-expression2/src/expression2/DApplyExpr.cpp | 32 +++++++++++++++++--
 xo-reader2/src/reader2/DProgressSsm.cpp       | 28 ++++++++++++++--
 2 files changed, 55 insertions(+), 5 deletions(-)

diff --git a/xo-expression2/src/expression2/DApplyExpr.cpp b/xo-expression2/src/expression2/DApplyExpr.cpp
index ce5e1951..ffc6372a 100644
--- a/xo-expression2/src/expression2/DApplyExpr.cpp
+++ b/xo-expression2/src/expression2/DApplyExpr.cpp
@@ -3,8 +3,9 @@
  *  @author Roland Conybeare, Jan 2026
  **/
 
-#include "DApplyExpr.hpp"
 #include "Expression.hpp"
+#include "DApplyExpr.hpp"
+#include "detail/IExpression_DApplyExpr.hpp"
 #include <xo/printable2/Printable.hpp>
 #include <xo/facet/FacetRegistry.hpp>
 
@@ -15,7 +16,34 @@ namespace xo {
     using xo::mm::AGCObject;
 
     namespace scm {
-        /* incomplete! */
+        obj<AExpression,DApplyExpr>
+        DApplyExpr::make2(obj<AAllocator> mm,
+                          TypeRef typeref,
+                          obj<AExpression> fn_expr,
+                          obj<AExpression> arg1,
+                          obj<AExpression> arg2)
+        {
+            return obj<AExpression,DApplyExpr>
+                       (DApplyExpr::_make2(mm, typeref, fn_expr, arg1, arg2));
+        }
+
+        DApplyExpr *
+        DApplyExpr::_make2(obj<AAllocator> mm,
+                           TypeRef typeref,
+                           obj<AExpression> fn_expr,
+                           obj<AExpression> arg1,
+                           obj<AExpression> arg2)
+        {
+            DApplyExpr * result
+                = DApplyExpr::scaffold(mm, typeref, fn_expr, 2 /*n_args*/);
+
+            result->assign_arg(0, arg1);
+            result->assign_arg(1, arg2);
+
+            return result;
+        }
+
+        /* incomplete, in the sense that does not populate args_[] */
         DApplyExpr::DApplyExpr(TypeRef typeref,
                                obj<AExpression> fn_expr,
                                size_type n_args) : typeref_{typeref},
diff --git a/xo-reader2/src/reader2/DProgressSsm.cpp b/xo-reader2/src/reader2/DProgressSsm.cpp
index cfed858f..cc0fc14b 100644
--- a/xo-reader2/src/reader2/DProgressSsm.cpp
+++ b/xo-reader2/src/reader2/DProgressSsm.cpp
@@ -9,9 +9,15 @@
 #include "DExpectExprSsm.hpp"
 #include "ssm/ISyntaxStateMachine_DExpectExprSsm.hpp"
 
+#include <xo/expression2/DApplyExpr.hpp>
+#include <xo/expression2/detail/IExpression_DApplyExpr.hpp>
 
 #include <xo/expression2/DConstant.hpp>
 #include <xo/expression2/detail/IExpression_DConstant.hpp>
+
+#include <xo/procedure2/init_primitives.hpp>  // for xo::scm::Primitives
+#include <xo/procedure2/detail/IGCObject_DPrimitive_gco_2_gco_gco.hpp>
+
 #ifdef NOT_YET
 #include "DApplySsm.hpp"
 #include "ssm/ISyntaxStateMachine_DApplySsm.hpp"
@@ -1179,20 +1185,36 @@ namespace xo {
                 break;
 
             case optype::op_multiply:
-#ifdef NOT_YET
                 {
+                    auto pm_obj = with_facet<AGCObject>::mkobj(&Primitives::s_mul_gco_gco_pm);
+
+                    auto fn_expr = DConstant::make(p_psm->expr_alloc(), pm_obj);
+
                     /* note:
                      * 1. don't assume we know lhs_ / rhs_ value types yet.
                      *    perhaps have expression like
                      *      f(..) * g(..)
                      *    where f is the function that contains current ssm.
+                     *
                      * 2. consequence: we need representation for
                      *    polymorphic multiply on unknown numeric arguments.
+                     *
+                     * 3. TypeRef::dwim(..) is a placeholder.
+                     *    Plan to later provide abstract interpreter
+                     *    (ie compiler pass :) to drive type inference/unification
+                     *
+                     * 4. Alternatively could supply type-annotation syntax
+                     *    so human can assist inference; context here is we want
+                     *    to automate the boring stuff
                      */
 
-                    DApplyExpr::make2();
+                    TypeRef tref = TypeRef::dwim
+                                       (TypeRef::prefix_type::from_chars("_mul_gco"),
+                                        nullptr);
+
+                    return DApplyExpr::make2(p_psm->expr_alloc(),
+                                             tref, fn_expr, lhs_, rhs_);
                 }
-#endif
 
                 break;
             case optype::op_divide: