CODEWITHSUNDEEP
compiler-constructionocamlyacclexabstract-syntax-tree
pbp
pbp

Reputation: 1481

Tracking source position of AST nodes in a compiler (ocaml)

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.

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

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

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

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

in every match which is a waste of space.

What's the best way to solve this?

Upvotes: 4

Views: 523

Answers (1)

Thomas
Thomas

Reputation: 5048

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 }

and then:

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

Upvotes: 5

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