change code structure

nasal_ast.h

@@ -4,32 +4,63 @@
 enum ast_node
 {
     ast_null=0,
-    ast_root,
-    ast_block,
-    ast_file, // ast_file is only used to store which file the subtree is on,codegen will generate nothing
-    ast_nil,ast_num,ast_str,ast_id,ast_func,ast_hash,ast_vec,
-    ast_hashmember,
-    ast_call,ast_callh,ast_callv,ast_callf,
-    ast_subvec,
-    ast_args,ast_default,ast_dynamic,
-    ast_and,ast_or,
-    ast_equal,
-    ast_addeq,ast_subeq,
-    ast_multeq,ast_diveq,
-    ast_lnkeq,
-    ast_cmpeq,ast_neq,
-    ast_less,ast_leq,
-    ast_grt,ast_geq,
-    ast_add,ast_sub,
-    ast_mult,ast_div,
-    ast_link,
-    ast_neg,ast_not,
-    ast_trino,
-    ast_for,ast_forindex,ast_foreach,ast_while,ast_new_iter,
-    ast_conditional,ast_if,ast_elsif,ast_else,
-    ast_multi_id,ast_multi_scalar,
-    ast_def,ast_multi_assign,
-    ast_continue,ast_break,ast_ret
+    ast_root,    // mark the root node of ast
+    ast_block,   // expression block 
+    ast_file,    // used to store which file the sub-tree is on
+    ast_nil,     // nil keyword
+    ast_num,     // number, basic value type
+    ast_str,     // string, basic value type
+    ast_id,      // identifier
+    ast_func,    // func keyword
+    ast_hash,    // hash, basic value type
+    ast_vec,     // vector, basic value type
+    ast_hashmember,// elements 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_args,    // 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_cmpeq,   // ==
+    ast_neq,     // !=
+    ast_less,    // <
+    ast_leq,     // <=
+    ast_grt,     // >
+    ast_geq,     // >=
+    ast_add,     // +
+    ast_sub,     // -
+    ast_mult,    // *
+    ast_div,     // /
+    ast_link,    // ~
+    ast_neg,     // -
+    ast_not,     // ~
+    ast_trino,   // ?:
+    ast_for,     // for keyword
+    ast_forindex,// forindex keyword
+    ast_foreach, // foreach keyword
+    ast_while,   // while
+    ast_new_iter,// iterator, used in forindex/foreach
+    ast_conditional,// 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_multi_scalar,// multi value sub-tree
+    ast_def,     // definition
+    ast_multi_assign,// multi assignment sub-tree
+    ast_continue,// continue keyword
+    ast_break,   // break keyword
+    ast_ret      // return keyword
 };
 
 const char* ast_name[]=
@@ -38,29 +69,61 @@ const char* ast_name[]=
     "root",
     "block",
     "file",
-    "nil","num","str","id","func","hash","vec",
+    "nil",
+    "num",
+    "str",
+    "id",
+    "func",
+    "hash",
+    "vec",
     "hashmember",
-    "call","callh","callv","callf",
+    "call",
+    "callh",
+    "callv",
+    "callf",
     "subvec",
-    "args","default","dynamic",
-    "and","or",
+    "args",
+    "default",
+    "dynamic",
+    "and",
+    "or",
     "=",
-    "+=","-=",
-    "*=","/=",
+    "+=",
+    "-=",
+    "*=",
+    "/=",
     "~=",
-    "==","!=",
-    "<","<=",
-    ">",">=",
-    "+","-",
-    "*","/",
+    "==",
+    "!=",
+    "<",
+    "<=",
+    ">",
+    ">=",
+    "+",
+    "-",
+    "*",
+    "/",
     "~",
-    "unary-","unary!",
+    "unary-",
+    "unary!",
     "trino",
-    "for","forindex","foreach","while","iter",
-    "conditional","if","elsif","else",
-    "multi_id","multi_scalar",
-    "def","multi_assign",
-    "continue","break","return"
+    "for",
+    "forindex",
+    "foreach",
+    "while",
+    "iter",
+    "conditional",
+    "if",
+    "elsif",
+    "else",
+    "multi_id",
+    "multi_scalar",
+    "def",
+    "multi_assign",
+    "continue",
+    "break",
+    "return",
+    nullptr
 };
 
 class nasal_ast