prepare to use new ast

ast/nasal_new_ast.cpp

@@ -0,0 +1,19 @@
+#include "nasal_new_ast.h"
+
+bool stmt::accept(ast_visitor* visitor) {
+    visitor->visit_stmt(this);
+    return true;
+}
+
+bool expr::accept(ast_visitor* visitor) {
+    visitor->visit_expr(this);
+    return true;
+}
+
+void ast_visitor::visit_stmt(stmt* node) {
+    node->accept(this);
+}
+
+void ast_visitor::visit_expr(expr* node) {
+    node->accept(this);
+}

ast/nasal_new_ast.h

@@ -0,0 +1,112 @@
+#pragma once
+
+#include "nasal.h"
+#include "nasal_err.h"
+
+enum class ast_node_type:u32 {
+    ast_null=0,      // null node
+    ast_stmt,
+    ast_expr,
+    ast_root,        // mark the root node of ast
+    ast_block,       // expression block 
+    ast_file,        // used to store which file the sub-tree is on, only used in main block
+    ast_nil,         // nil keyword
+    ast_num,         // number, basic value type
+    ast_str,         // string, basic value type
+    ast_id,          // identifier
+    ast_bool,        // bools
+    ast_func,        // func keyword
+    ast_hash,        // hash, basic value type
+    ast_vec,         // vector, basic value type
+    ast_pair,        // pair of key and value in hashmap
+    ast_call,        // mark a sub-tree of calling an identifier
+    ast_callh,       // id.name
+    ast_callv,       // id[index]
+    ast_callf,       // id()
+    ast_subvec,      // id[index:index]
+    ast_params,      // mark a sub-tree of function parameters
+    ast_default,     // default parameter
+    ast_dynamic,     // dynamic parameter
+    ast_and,         // and keyword
+    ast_or,          // or keyword
+    ast_equal,       // =
+    ast_addeq,       // +=
+    ast_subeq,       // -=
+    ast_multeq,      // *=
+    ast_diveq,       // /=
+    ast_lnkeq,       // ~=
+    ast_btandeq,     // &=
+    ast_btoreq,      // |=
+    ast_btxoreq,     // ^=
+    ast_cmpeq,       // ==
+    ast_neq,         // !=
+    ast_less,        // <
+    ast_leq,         // <=
+    ast_grt,         // >
+    ast_geq,         // >=
+    ast_add,         // +
+    ast_sub,         // -
+    ast_mult,        // *
+    ast_div,         // /
+    ast_link,        // ~
+    ast_neg,         // unary -
+    ast_lnot,        // unary !
+    ast_bnot,        // unary ~ bitwise not
+    ast_bitor,       // bitwise or
+    ast_bitxor,      // bitwise xor
+    ast_bitand,      // bitwise and
+    ast_trino,       // ?:
+    ast_for,         // for keyword
+    ast_forindex,    // forindex keyword
+    ast_foreach,     // foreach keyword
+    ast_while,       // while
+    ast_iter,        // iterator, used in forindex/foreach
+    ast_cond,        // mark a sub-tree of conditional expression
+    ast_if,          // if keyword
+    ast_elsif,       // elsif keyword
+    ast_else,        // else keyword
+    ast_multi_id,    // multi identifiers sub-tree
+    ast_tuple,       // tuple, only used in multiple assignment
+    ast_def,         // definition
+    ast_multi_assign,// multi assignment sub-tree
+    ast_continue,    // continue keyword, only used in loop
+    ast_break,       // break keyword, only used in loop
+    ast_ret          // return keyword, only used in function block
+};
+
+class ast_visitor;
+
+class ast_node {
+private:
+    span nd_loc;
+    ast_node_type nd_type;
+public:
+    ast_node(const span& location,ast_node_type node_type):
+        nd_loc(location), nd_type(node_type) {}
+    ~ast_node() = default;
+    virtual bool accept(ast_visitor*) = 0;
+};
+
+class stmt:public ast_node {
+public:
+    stmt(const span& location,ast_node_type node_type):
+        ast_node(location, node_type) {}
+    ~stmt() = default;
+    virtual bool accept(ast_visitor*);
+};
+
+class expr:public ast_node {
+private:
+
+public:
+    expr(const span& location,ast_node_type node_type):
+        ast_node(location, node_type) {}
+    ~expr() = default;
+    virtual bool accept(ast_visitor*);
+};
+
+class ast_visitor {
+public:
+    virtual void visit_stmt(stmt*);
+    virtual void visit_expr(expr*);
+};