From d6371ee3694a37aeea9f6b8f2e91d23e87d409f8 Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Thu, 13 Jun 2024 16:20:53 -0400
Subject: [PATCH] xo-expression: + Apply expressions

---
 include/xo/expression/Apply.hpp              | 40 ++++++++++++++++----
 include/xo/expression/Primitive.hpp          |  2 +
 include/xo/expression/PrimitiveInterface.hpp |  1 +
 include/xo/expression/exprtype.hpp           |  9 +++++
 src/expression/Apply.cpp                     | 19 ++++++++++
 src/expression/CMakeLists.txt                |  1 +
 6 files changed, 65 insertions(+), 7 deletions(-)
 create mode 100644 src/expression/Apply.cpp

diff --git a/include/xo/expression/Apply.hpp b/include/xo/expression/Apply.hpp
index 518415f0..56f6b886 100644
--- a/include/xo/expression/Apply.hpp
+++ b/include/xo/expression/Apply.hpp
@@ -11,21 +11,47 @@
 
 namespace xo {
     namespace ast {
+
         /** @class Apply
          *  @brief syntax for a function call.
          *
          *  In general we don't know function to be invoked
          *  until runtime,  depending on the nature of Expression.
-         *
-         *  For first cut,  we'll just handle the case of a Constant
-         *  that refers to a known function
          **/
         class Apply : public Expression {
-            ref::rp<Expression> fn_;
-            std::vector<ref::rp<Expression>> args_;
-        };
-    } /*namespace ast*/
+        public:
+            Apply(const ref::rp<Expression> & fn,
+                  const std::vector<ref::rp<Expression>> & argv)
+                : Expression(exprtype::apply), fn_{fn}, argv_(argv)
+                {}
 
+            /** downcast from Expression **/
+            static ref::brw<Apply> from(ref::brw<Expression> x) {
+                return ref::brw<Apply>::from(x);
+            }
+
+            const ref::rp<Expression> & fn() const { return fn_; }
+            const std::vector<ref::rp<Expression>> & argv() const { return argv_; }
+
+            virtual void display(std::ostream & os) const;
+
+        private:
+            /** function to invoke **/
+            ref::rp<Expression> fn_;
+            /** argument expressions,  in l-to-r order **/
+            std::vector<ref::rp<Expression>> argv_;
+        }; /*Apply*/
+
+        inline ref::rp<Apply>
+        make_apply(const ref::rp<Expression> & fn,
+                              const ref::rp<Expression> & arg1) {
+            std::vector<ref::rp<Expression>> argv;
+            argv.push_back(arg1);
+
+            return new Apply(fn, argv);
+        } /*make_apply*/
+
+    } /*namespace ast*/
 } /*namespace xo*/
 
 
diff --git a/include/xo/expression/Primitive.hpp b/include/xo/expression/Primitive.hpp
index e0de42d7..afae94a9 100644
--- a/include/xo/expression/Primitive.hpp
+++ b/include/xo/expression/Primitive.hpp
@@ -42,6 +42,8 @@ namespace xo {
             // ----- PrimitiveInterface -----
 
             virtual std::string const & name() const { return name_; }
+            /** FIXME for now **/
+            virtual int n_arg() const { return 1; }
 
             // ----- ConstantInterface -----
 
diff --git a/include/xo/expression/PrimitiveInterface.hpp b/include/xo/expression/PrimitiveInterface.hpp
index 54e51451..c294a440 100644
--- a/include/xo/expression/PrimitiveInterface.hpp
+++ b/include/xo/expression/PrimitiveInterface.hpp
@@ -22,6 +22,7 @@ namespace xo {
             }
 
             virtual const std::string & name() const = 0;
+            virtual int n_arg() const = 0;
 
             //virtual TypeDescr value_td() const override = 0;
             //virtual TaggedPtr value_tp() const override = 0;
diff --git a/include/xo/expression/exprtype.hpp b/include/xo/expression/exprtype.hpp
index fe810bb7..1988f7e9 100644
--- a/include/xo/expression/exprtype.hpp
+++ b/include/xo/expression/exprtype.hpp
@@ -5,6 +5,7 @@
 
 #pragma once
 
+#include <ostream>
 #include <cstdint>
 
 namespace xo {
@@ -44,6 +45,14 @@ namespace xo {
 
         /** @brief number of built-in expression types,  repr convenient for array sizing **/
         static constexpr std::size_t n_exprtype = static_cast<std::size_t>(exprtype::n_expr);
+
+        inline std::ostream &
+        operator<<(std::ostream & os,
+                   exprtype x)
+        {
+            os << expr2str(x);
+            return os;
+        }
     } /*namespace ast*/
 } /*namespace xo*/
 
diff --git a/src/expression/Apply.cpp b/src/expression/Apply.cpp
new file mode 100644
index 00000000..781ec170
--- /dev/null
+++ b/src/expression/Apply.cpp
@@ -0,0 +1,19 @@
+/* @file Apply.cpp */
+
+#include "Apply.hpp"
+#include "xo/indentlog/print/vector.hpp"
+
+namespace xo {
+    namespace ast {
+        void
+        Apply::display(std::ostream & os) const {
+            os << "<Apply"
+               << xtag("fn", fn_)
+               << xtag("argv", argv_)
+               << ">";
+        }
+    } /*namespace ast*/
+} /*namespace xo*/
+
+
+/* end Apply.cpp */
diff --git a/src/expression/CMakeLists.txt b/src/expression/CMakeLists.txt
index 94e74d0c..59e754a5 100644
--- a/src/expression/CMakeLists.txt
+++ b/src/expression/CMakeLists.txt
@@ -3,6 +3,7 @@
 set(SELF_LIB xo_expression)
 set(SELF_SRCS
     Expression.cpp
+    Apply.cpp
     #init_reflect.cpp
 )