functional programming - How to shorten this OCaml code? -

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i wondering how shorten these code suspect redundant

let ename doc =    try (stringmap.find ename doc) not_found -> none;;  let get_double ename doc =    let element = ename doc in   match element     | none -> none     | (double v) -> v     | _ -> raise wrong_bson_type;;  let get_string ename doc =    let element = ename doc in   match element     | none -> none     | (string v) -> v     | _ -> raise wrong_bson_type;;  let get_doc ename doc =    let element = ename doc in   match element     | none -> none     | (document v) -> v     | _ -> raise wrong_bson_type;;

so, basically, have different types of values, , put kinds of values map.

the code above getting according type of values out of map. each type, have get. 1 type of value, have see a). whether there or not; b). whether type indeed, if not, raise exception.

but code above seems redundant can see. diff between each type's type itself.

how can shorten code?

you can this:

let get_generic extract ename doc =   let element = ename doc in   match element     | none -> none     | v -> (extract v)  let get_double = get_generic (function double v -> v | _ -> raise wrong_bson_type) let get_string = get_generic (function string v -> v | _ -> raise wrong_bson_type) let get_doc = get_generic (function document v -> v | _ -> raise wrong_bson_type)

edit: remove redundant raise wrong_bson_type (but ugly):

let get_generic extract ename doc = try   let element = ename doc in   match element     | none -> none     | v -> (extract v) match_failure _ -> raise wrong_bson_type  let get_double = get_generic (fun (double v) -> v) let get_string = get_generic (fun (string v) -> v) let get_doc = get_generic (fun (document v)-> v)

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