xo-expression2: + DApplyExpr [WIP]. Builds, not used or tested

include/xo/expression2/DApplyExpr.hpp

@@ -0,0 +1,64 @@
+/** @file DApplyExpr.hpp
+ *
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#pragma once
+
+#include "Expression.hpp"
+#include "TypeRef.hpp"
+#include "exprtype.hpp"
+#include <xo/object2/DArray.hpp>
+#include <xo/reflect/TypeDescr.hpp>
+#include <xo/indentlog/print/pretty.hpp>
+
+namespace xo {
+    namespace scm {
+
+        /** @class DApplyExpr
+         *  @brief syntax for a procedure/function call
+         **/
+        class DApplyExpr {
+        public:
+            using TypeDescr = xo::reflect::TypeDescr;
+            using ppindentinfo = xo::print::ppindentinfo;
+            using size_type = std::size_t;
+
+        public:
+
+            obj<AExpression>  fn() const noexcept { return fn_; }
+            const DArray * args() const noexcept { return args_; }
+
+            size_type n_arg() const noexcept { return args_->size(); }
+            obj<AExpression> arg(size_type i) const;
+
+            /** @defgroup scm-applyexpr-expression-facet **/
+            ///@{
+
+            exprtype extype() const noexcept { return exprtype::apply; }
+            TypeRef typeref() const noexcept { return typeref_; }
+            TypeDescr valuetype() const noexcept { return typeref_.td(); }
+            void assign_valuetype(TypeDescr td) noexcept;
+
+            ///@}
+            /** @defgroup scm-applyexpr-printable-facet **/
+            ///@{
+
+            bool pretty(const ppindentinfo & ppii) const;
+
+            ///@}
+
+        private:
+            /** expression value always has type consistent
+             *  with this description
+             **/
+            TypeRef typeref_;
+            /** expression for function/procedure to invoke **/
+            obj<AExpression> fn_;
+            /** expression for each argument vector **/
+            const DArray * args_;
+        };
+    }
+}
+
+/* end DApplyExpr.hpp */

include/xo/expression2/DVariable.hpp

@@ -15,7 +15,7 @@
 namespace xo {
     namespace scm {
 
-        /** @class DVariable*
+        /** @class DVariable
          *  @brief syntax for a variable reference
          **/
         class DVariable {

include/xo/expression2/exprtype.hpp

@@ -29,8 +29,10 @@ namespace xo {
 #ifdef NOT_YET
             /** variable assignment **/
             assign,
+#endif
             /** function call **/
             apply,
+#ifdef NOT_YET
             /** function definition **/
             lambda,
 #endif
@@ -61,7 +63,9 @@ namespace xo {
             case exprtype::define: return "define";
 #ifdef NOT_YET
             case exprtype::assign: return "assign";
+#endif
             case exprtype::apply: return "apply";
+#ifdef NOT_YET
             case exprtype::lambda: return "lambda";
             case exprtype::variable: return "variable";
             case exprtype::ifexpr: return "if_expr";

src/expression2/CMakeLists.txt

@@ -7,6 +7,7 @@ set(SELF_SRCS
     DConstant.cpp
     DVariable.cpp
     DDefineExpr.cpp
+    DApplyExpr.cpp
 
     TypeRef.cpp
 

src/expression2/DApplyExpr.cpp

@@ -0,0 +1,95 @@
+/** @file DApplyExpr.cpp
+ *
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#include "DApplyExpr.hpp"
+#include "Expression.hpp"
+#include <xo/printable2/Printable.hpp>
+#include <xo/facet/FacetRegistry.hpp>
+
+namespace xo {
+    using xo::print::APrintable;
+    using xo::facet::FacetRegistry;
+    using xo::mm::AGCObject;
+
+    namespace scm {
+        obj<AExpression>
+        DApplyExpr::arg(size_type i) const
+        {
+            if (i >= args_->size()) [[unlikely]] {
+                throw std::runtime_error(tostr("attempt to fetch argument i where [0..n) expected",
+                                               xtag("i", i),
+                                               xtag("n", args_->size()),
+                                               xtag("src", "DApplyExpr::arg")));
+            }
+
+            obj<AGCObject> arg_i = args_->at(i);
+
+            auto expr_i = FacetRegistry::instance().variant<AExpression>(arg_i);
+
+            if (!expr_i) [[unlikely]] {
+                throw std::runtime_error(tostr("expected expression interface on argument i",
+                                               xtag("i", i),
+                                               xtag("arg[i]", arg_i)));
+            }
+
+            return expr_i;
+        }
+
+        void
+        DApplyExpr::assign_valuetype(TypeDescr td) noexcept {
+            typeref_.resolve(td);
+        }
+
+        bool
+        DApplyExpr::pretty(const ppindentinfo & ppii) const {
+            using xo::print::ppstate;
+
+            ppstate * pps = ppii.pps();
+
+            if (ppii.upto()) {
+                /* perhaps print on one line */
+                if (!pps->print_upto("<ApplyExpr"))
+                    return false;
+
+                {
+                    obj<APrintable> fn
+                        = FacetRegistry::instance().variant<APrintable>(fn_);
+                    if (!pps->print_upto(refrtag("fn", fn)))
+                        return false;
+                }
+
+                for (size_t i_arg = 0, n_arg = this->n_arg(); i_arg < n_arg; ++i_arg) {
+                    obj<APrintable> arg_i
+                        = FacetRegistry::instance().variant<APrintable>(this->arg(i_arg));
+
+                    if (!pps->print_upto(refrtag(concat("arg", 1+i_arg), arg_i)))
+                        return false;
+                }
+
+                return true;
+            } else {
+                pps->write("<ApplyExpr");
+
+                obj<APrintable> fn
+                    = FacetRegistry::instance().variant<APrintable>(fn_);
+
+                pps->newline_indent(ppii.ci1());
+                pps->pretty(refrtag("fn", fn));
+
+                for (size_t i_arg = 0, n_arg = this->n_arg(); i_arg < n_arg; ++i_arg) {
+                    obj<APrintable> arg_i
+                        = FacetRegistry::instance().variant<APrintable>(fn_);
+
+                    pps->newline_indent(ppii.ci1());
+                    pps->pretty(refrtag(concat("arg", 1+i_arg), arg_i));
+                }
+                return false;
+            }
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DApplyExpr.cpp */