Question

In case I have to disassemble a data type as its variable size, can I still use the “match and with, and if the answer is yes you could help me figure out how (I’m a beginner with this language), or do I or use other methods.

the type defined is this :

type 'state formula = 
  | And      of 'state formula list
  | Or       of 'state formula list
  | Literal  of bool
  | Variable of 'state  

from the examples I’ve seen the “match and with” is used when the structure of the static type was, in my case as I do?

Answer 1

So here’s an example which uses match to work with your formula type:

type 'state formula = | And of 'state formula list | Or of 'state formula list | Literal of bool | Variable of 'state

let rec count_vars form = match form with
| And forms 
| Or forms -> List.fold_left (+) 0 (List.map count_vars forms)
| Literal _ -> 0
| Variable _ -> 1

let formula = And [ Variable "q0"; Or[ Variable "q1";Variable "q2"]; Variable "q3"]

let vars_in_formula = count_vars formula (* 4 *)