I'm learning OCaml these days by some basic material and a project written in OCaml. But I don't understand some symbols in OCaml. For example:
open Batteries
type char_token = [
| `Char of int
| `Escape of char list
]
what's these things with symbol ` mean?
And also other symbols are hard for me to understand:
I can't find anything in the OCaml Manual. Can somebody explain more details about the symbols above? Or just recommend some material to me ?
`Foo and [> are polymorphic variants (http://caml.inria.fr/pub/docs/manual-ocaml-4.00/manual006.html#toc36). They are probably not worth it for a beginner, but you could look at one of my old answers (Extending an existing type in OCaml) to see how to use them.
_ is a pattern that matches anything:
let head l = match l with
| x :: _ -> x
| _ -> failwith "empty list"
Both _ there are used to say to the compiler "something I don't care about".