Add 'xo-expression/' from commit '5ac3c03a0c'

git-subtree-dir: xo-expression
git-subtree-mainline: d0f5ccc1ce
git-subtree-split: 5ac3c03a0c

xo-expression/include/xo/expression/Sequence.hpp

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+/** @file Sequence.hpp
+ *
+ *  Author: Roland Conybeare
+ **/
+
+#pragma once
+
+#include "Expression.hpp"
+//#include <cstdint>
+
+namespace xo {
+    namespace ast {
+        class Sequence : public Expression {
+        public:
+            Sequence(const std::vector<rp<Expression>> & xv)
+                : Expression(exprtype::sequence,
+                             xv[xv.size() - 1]->valuetype()),
+                  expr_v_(xv) {}
+
+            static rp<Sequence> make(const std::vector<rp<Expression>> & xv) { return new Sequence(xv); }
+
+            std::size_t size() const { return expr_v_.size(); }
+            const rp<Expression> & operator[](std::size_t i) const { return expr_v_[i]; }
+
+            // ----- from Expression -----
+
+            /** note: broken if .expr_v_ contains any def-exprs
+             *  (will treat references to so-defined vars as free).
+             *  must rewrite these first
+             **/
+            virtual std::set<std::string> get_free_variables() const override;
+            virtual std::size_t visit_preorder(VisitFn visitor_fn) override;
+            /** note: borken if .expr_v_ contains any def-exprs **/
+            virtual std::size_t visit_layer(VisitFn visitor_fn) override;
+            virtual rp<Expression> xform_layer(TransformFn visitor_fn) override;
+            virtual void attach_envs(ref::brw<Environment> parent) override;
+
+            // ----- from GeneralizedExpression ----
+
+            virtual void display(std::ostream & os) const override;
+
+        private:
+            /** sequence of expressions;  evaluate in left-to-right order.
+             **/
+            std::vector<rp<Expression>> expr_v_;
+        };
+    } /*namespace ast*/
+
+} /*namespace xo*/
+
+
+/** end Sequence.hpp **/