跟踪AST节点在编译器(ocaml)中的源位置 [英] Tracking source position of AST nodes in a compiler (ocaml)

问题描述

我正在使用ocamllex/yacc用ocaml编写编译器.一切进展顺利，但我遇到了设计问题.对于我创建的每个AST节点，最好在源代码中包含有关该节点的行/字符位置的信息.这对于以后向用户提供错误消息很有用.

I'm writing a compiler in ocaml, using ocamllex/yacc. Things are going well, but I've a design problem. For each AST node I create, it'd be good to have information about line/character position of that node in the source code. That would be useful for providing error messages to the user later.

现在，我可以向节点添加某种元类型:

Now, I can add some kind of meta type to my nodes:

type node = Node1 of ... * meta | Node2 of ... * meta

但这似乎是多余的.稍后，当我完成对AST的验证后，我将不得不写

but that seems redundant. Later, when I'm done with verifying the AST, I'll have to write

match n with 
| NodeX(..., _) -> ...

每个match中的

都是浪费空间.

in every match which is a waste of space.

解决此问题的最佳方法是什么?

What's the best way to solve this?

推荐答案

解决此问题的常用方法是使用记录保存元信息和节点表达式:

The usual way to solve this is to use a record to hold the meta-information and the node expression:

type node_exp = Node1 of ... | Node2 of ...
and node = { exp: node_exp; meta: meta }

然后:

match n.exp with
  | NodeX ... -> ...

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