“Eval” a string in OCaml

Question

I'm trying to "eval" a string representing an OCaml expression in OCaml. I'm looking to do something equivalent to Python's eval.

So far I've not been able to find much. The Parsing module looks like it could be helpful, but I was not able to find a way to just eval a string.

Edgar Aroutiounian Edgar Aroutiounian · Accepted Answer · 2015-10-23T00:44:17

Here is how to do it, but I didn't tell you. (Also the Parsing module is about Parsing, not executing code)

#require "compiler-libs" (* Assuming you're using utop, if compiling then this is the package you need *)
let eval code =
  let as_buf = Lexing.from_string code in
  let parsed = !Toploop.parse_toplevel_phrase as_buf in
  ignore (Toploop.execute_phrase true Format.std_formatter parsed)

example:

eval "let () = print_endline \"hello\";;"

Notice the trailing ;; in the code sample.

To use ocamlbuild, you will need to use both compiler-libs and compiler-libs.toplevel.

“Eval” a string in OCaml

2 Answers