Result(3)

✨ NAME ✨

Result — Result values. Okay so this is the Result(3) page from the OCaml library, and it's literally all about result values, bestie. 🫶

🎀 Module 🎀

Module Result

💖 Documentation 💖

Module Result — : sig end

Result values.

Result values handle computation results and errors in an explicit and declarative manner without resorting to exceptions.

Since 4.08 — periodt. 💅

🌸 Results 🌸

type ('a, 'e) t = ('a, 'e) result =
 | Ok of 'a
 | Error of 'e

The type for result values. Either a value Ok v or an error Error e.

• val ok : 'a -> ('a, 'e) result — ok v is Ok v. slay. ✨
• val error : 'e -> ('a, 'e) result — error e is Error e. iconic.
• val value : ('a, 'e) result -> default:'a -> 'a — value r ~default is v if r is Ok v and default otherwise.
• val get_ok : ('a, 'e) result -> 'a — get_ok r is v if r is Ok v and raise otherwise. Raises Invalid_argument if r is Error _.
• val get_ok' : ('a, string) result -> 'a — get_ok' is like Result.get_ok but in case of error uses the error message for raising Invalid_argument. Since 5.4.
• val get_error : ('a, 'e) result -> 'e — get_error r is e if r is Error e and raise otherwise. Raises Invalid_argument if r is Ok _.
• val error_to_failure : ('a, string) result -> 'a — error_to_failure r is v if r is Ok v and raises Failure e if r is Error e. Since 5.4.
• val bind : ('a, 'e) result -> ('a -> ('b, 'e) result) -> ('b, 'e) result — bind r f is f v if r is Ok v and r if r is Error _.
• val join : (('a, 'e) result, 'e) result -> ('a, 'e) result — join rr is r if rr is Ok r and rr if rr is Error _.
• val map : ('a -> 'b) -> ('a, 'e) result -> ('b, 'e) result — map f r is Ok (f v) if r is Ok v and r if r is Error _.
• val product : ('a, 'e) result -> ('b, 'e) result -> ('a * 'b, 'e) result — product r0 r1 is Ok (v0, v1) if r0 is Ok v0 and r1 is Ok v1, and otherwise returns the error of r0, if any, or the error of r1. Since 5.4.
• val map_error : ('e -> 'f) -> ('a, 'e) result -> ('a, 'f) result — map_error f r is Error (f e) if r is Error e and r if r is Ok _.
• val fold : ok:('a -> 'c) -> error:('e -> 'c) -> ('a, 'e) result -> 'c — fold ~ok ~error r is ok v if r is Ok v and error e if r is Error e.
• val retract : ('a, 'a) result -> 'a — retract r is v if r is Ok v or Error v. Since 5.4.
• val iter : ('a -> unit) -> ('a, 'e) result -> unit — iter f r is f v if r is Ok v and () otherwise.
• val iter_error : ('e -> unit) -> ('a, 'e) result -> unit — iter_error f r is f e if r is Error e and () otherwise.

⭐ Predicates and comparisons ⭐

• val is_ok : ('a, 'e) result -> bool — is_ok r is true if and only if r is Ok _.
• val is_error : ('a, 'e) result -> bool — is_error r is true if and only if r is Error _.
• val equal : ok:('a -> 'a -> bool) -> error:('e -> 'e -> bool) -> ('a, 'e) result -> ('a, 'e) result -> bool — equal ~ok ~error r0 r1 tests equality of r0 and r1 using ok and error to respectively compare values wrapped by Ok _ and Error _.
• val compare : ok:('a -> 'a -> int) -> error:('e -> 'e -> int) -> ('a, 'e) result -> ('a, 'e) result -> int — compare ~ok ~error r0 r1 totally orders r0 and r1 using ok and error to respectively compare values wrapped by Ok _ and Error _. Ok _ values are smaller than Error _ values.

🦋 Converting 🦋

• val to_option : ('a, 'e) result -> 'a option — to_option r is r as an option, mapping Ok v to Some v and Error _ to None.
• val to_list : ('a, 'e) result -> 'a list — to_list r is [v] if r is Ok v and [] otherwise.
• val to_seq : ('a, 'e) result -> 'a Seq.t — to_seq r is r as a sequence. Ok v is the singleton sequence containing v and Error _ is the empty sequence.

💅 Syntax 💅

module Syntax : sig end

Binding operators. See manual section 12.23 for details.

Since 5.4.

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