init

Prework/visitor.h

@@ -0,0 +1,60 @@
+// 你不可以修改这份代码
+#pragma once
+#include <any>
+
+struct visitor;
+
+struct node {
+    virtual std::any accept(visitor *) = 0;
+    virtual ~node() = default;
+};
+
+struct num_node;
+struct add_node;
+struct sub_node;
+struct mul_node;
+struct div_node;
+
+struct visitor {
+    virtual std::any visit(node *ctx) { return ctx->accept(this); }
+    virtual std::any visit_num(num_node *) = 0;
+    virtual std::any visit_add(add_node *) = 0;
+    virtual std::any visit_sub(sub_node *) = 0;
+    virtual std::any visit_mul(mul_node *) = 0;
+    virtual std::any visit_div(div_node *) = 0;
+    virtual ~visitor() = default;
+};
+
+struct num_node final : node {
+    std::any number;
+    std::any accept(visitor *ctx) override { return ctx->visit_num(this); }
+    ~num_node() override = default;
+};
+
+struct add_node final : node {
+    node *lnode;
+    node *rnode;
+    std::any accept(visitor *ctx) override { return ctx->visit_add(this); }
+    ~add_node() override = default;
+};
+
+struct sub_node final : node {
+    node *lnode;
+    node *rnode;
+    std::any accept(visitor *ctx) override { return ctx->visit_sub(this); }
+    ~sub_node() override = default;
+};
+
+struct mul_node final : node {
+    node *lnode;
+    node *rnode;
+    std::any accept(visitor *ctx) override { return ctx->visit_mul(this); }
+    ~mul_node() override = default;
+};
+
+struct div_node final : node {
+    node *lnode;
+    node *rnode;
+    std::any accept(visitor *ctx) override { return ctx->visit_div(this); }
+    ~div_node() override = default;
+};