xo-expression: + AssignExpr

include/xo/expression/AssignExpr.hpp

@@ -0,0 +1,61 @@
+/* file AssignExpr.hpp
+ *
+ * author: Roland Conybeare, Aug 2024
+ */
+
+#pragma once
+
+#include "Expression.hpp"
+#include "Variable.hpp"
+
+namespace xo {
+    namespace ast {
+        /** @class AssignExpr
+         *  @brief Provide expression for assigning to a variable
+         *
+         *    def pi = 3.14159265;
+         *    def foo = 0.0;
+         *    foo := pi / 2;
+         **/
+        class AssignExpr : public Expression {
+        public:
+            static rp<AssignExpr> make(const rp<Variable> & lhs,
+                                       const rp<Expression> & rhs);
+
+            static ref::brw<AssignExpr> from(ref::brw<Expression> x) {
+                return ref::brw<AssignExpr>::from(x);
+            }
+
+            const rp<Variable> & lhs() const { return lhs_; }
+            const rp<Expression> & rhs() const { return rhs_; }
+
+            std::set<std::string> calc_free_variables() const;
+
+            // ----- inherited from Expression -----
+
+            virtual std::set<std::string> get_free_variables() const override;
+            virtual std::size_t visit_preorder(VisitFn visitor_fn) override;
+            virtual std::size_t visit_layer(VisitFn visitor_fn) override;
+            virtual rp<Expression> xform_layer(TransformFn xform_fn) override;
+            virtual void attach_envs(ref::brw<Environment> p) override;
+
+            virtual void display(std::ostream & os) const override;
+
+        private:
+            AssignExpr(const rp<Variable> & lhs,
+                       const rp<Expression> & rhs);
+
+        private:
+            /** assign to this variable. **/
+            rp<Variable> lhs_;
+            /** assign value of this expression to variable @p lhs **/
+            rp<Expression> rhs_;
+
+            /** free variables for this assignment **/
+            std::set<std::string> free_var_set_;
+        };
+    } /*namespace ast*/
+} /*namespace xo*/
+
+
+/* end AssignExpr.hpp */

include/xo/expression/exprtype.hpp

@@ -24,6 +24,8 @@ namespace xo {
             primitive,
             /** variable/function definition **/
             define,
+            /** variable assignment **/
+            assign,
             /** function call **/
             apply,
             /** function definition **/
@@ -49,6 +51,7 @@ namespace xo {
             case exprtype::constant: return "constant";
             case exprtype::primitive: return "primitive";
             case exprtype::define: return "define";
+            case exprtype::assign: return "assign";
             case exprtype::apply: return "apply";
             case exprtype::lambda: return "lambda";
             case exprtype::variable: return "variable";