From 20b23b50fc7c584f386361e0d794b3a9bc5f3b80 Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Thu, 13 Jun 2024 17:05:38 -0400
Subject: [PATCH] xo-expression: + Lambda (function definitions)

---
 include/xo/expression/Lambda.hpp   | 44 ++++++++++++++++++++++++++++++
 include/xo/expression/exprtype.hpp |  3 ++
 src/expression/CMakeLists.txt      |  1 +
 src/expression/Lambda.cpp          | 19 +++++++++++++
 4 files changed, 67 insertions(+)
 create mode 100644 include/xo/expression/Lambda.hpp
 create mode 100644 src/expression/Lambda.cpp

diff --git a/include/xo/expression/Lambda.hpp b/include/xo/expression/Lambda.hpp
new file mode 100644
index 00000000..581ba274
--- /dev/null
+++ b/include/xo/expression/Lambda.hpp
@@ -0,0 +1,44 @@
+/** @file Lambda.hpp
+ *
+ *  Author: Roland Conybeare
+ **/
+
+#pragma once
+
+#include "Expression.hpp"
+#include <vector>
+#include <string>
+//#include <cstdint>
+
+namespace xo {
+    namespace ast {
+        /** @class Lambda
+         *  @brief abstract syntax tree for a function definition
+         *
+         **/
+        class Lambda : public Expression {
+        public:
+            /** @p argv   Formal parameters, in left-to-right order
+             *  @p body   Expression for body of this function
+             **/
+            Lambda(const std::vector<std::string> & argv,
+                   const ref::rp<Expression> & body)
+                : Expression(exprtype::lambda), argv_{argv}, body_{body} {}
+
+            const std::vector<std::string> & argv() const { return argv_; }
+            const ref::rp<Expression> & body() const { return body_; }
+
+            // ----- Expression -----
+
+            virtual void display(std::ostream & os) const override;
+
+        private:
+            /** formal argument names **/
+            std::vector<std::string> argv_;
+            /** function body **/
+            ref::rp<Expression> body_;
+        }; /*Lambda*/
+    } /*namespace ast*/
+} /*namespace xo*/
+
+/** end Lambda.hpp **/
diff --git a/include/xo/expression/exprtype.hpp b/include/xo/expression/exprtype.hpp
index 1988f7e9..7afa8ff3 100644
--- a/include/xo/expression/exprtype.hpp
+++ b/include/xo/expression/exprtype.hpp
@@ -24,6 +24,8 @@ namespace xo {
             primitive,
             /** function call **/
             apply,
+            /** function definition **/
+            lambda,
 
             /** not an expression.  comes last, counts entries **/
             n_expr
@@ -37,6 +39,7 @@ namespace xo {
             case exprtype::constant: return "constant";
             case exprtype::primitive: return "primitive";
             case exprtype::apply: return "apply";
+            case exprtype::lambda: return "lambda";
             default: break;
             }
 
diff --git a/src/expression/CMakeLists.txt b/src/expression/CMakeLists.txt
index 59e754a5..5db806b2 100644
--- a/src/expression/CMakeLists.txt
+++ b/src/expression/CMakeLists.txt
@@ -4,6 +4,7 @@ set(SELF_LIB xo_expression)
 set(SELF_SRCS
     Expression.cpp
     Apply.cpp
+    Lambda.cpp
     #init_reflect.cpp
 )
 
diff --git a/src/expression/Lambda.cpp b/src/expression/Lambda.cpp
new file mode 100644
index 00000000..d228bb2c
--- /dev/null
+++ b/src/expression/Lambda.cpp
@@ -0,0 +1,19 @@
+/* @file Lambda.cpp */
+
+#include "Lambda.hpp"
+#include "xo/indentlog/print/vector.hpp"
+
+namespace xo {
+    namespace ast {
+        void
+        Lambda::display(std::ostream & os) const {
+            os << "<Lambda"
+               << xtag("argv", argv_)
+               << xtag("body", body_)
+               << ">";
+        } /*display*/
+    } /*namespace ast*/
+} /*namespace xo*/
+
+
+/* end Lambda.cpp */