Monadic results of computations that can raise exceptions
The type of a result. A result is either Ok x carrying the normal return value x or is Error e carrying some indication of an error. The value associated with a bad result is usually an exception (exn) that can be raised.
val ok : 'a -> ('a, 'b) tok v is Ok v.
val error : 'e -> ('a, 'e) terror e is Error e.
val value : ('a, 'e) t -> default:'a -> 'avalue r ~default is v if r is Ok v and default otherwise.
val default : 'a -> ('a, _) t -> 'adefault d r evaluates to d if r is Error else x when r is Ok x.
value or a slightly different signature.
val get_ok : ('a, 'e) t -> 'aget_ok r is v if r is Ok v and
Invalid_argument otherwise.
val get_error : ('a, 'e) t -> 'eget_error r is e if r is Error e and
Invalid_argument otherwise.
val get : ('a, exn) t -> 'aget (Ok x) returns x, and get (Error e) raises e. This function is, in a way, the opposite of the catch function
val catch : ('a -> 'e) -> 'a -> ('e, exn) tExecute a function and catch any exception as a result. This function encapsulates code that could throw an exception and returns that exception as a value.
val catch2 : ('a -> 'b -> 'c) -> 'a -> 'b -> ('c, exn) tAs catch but two parameters. This saves a closure construction
val catch3 : ('a -> 'b -> 'c -> 'd) -> 'a -> 'b -> 'c -> ('d, exn) tAs catch but three parameters. This saves a closure construction
bind r f is f v if r is Ok v and r if r is Error _.
join rr is r if rr is Ok r and rr if rr is Error _.
map f r is Ok (f v) if r is Ok v and r if r is Error _.
map_error f r is Error (f e) if r is Error e and r if r is Ok _.
map_both f g (Ok x) returns Ok (f x) and map_both f g (Error e) returns Error (g e).
val map_default : 'b -> ('a -> 'b) -> ('a, _) t -> 'bmap_default d f r evaluates to d if r is Error else f x when r is Ok x
val fold : ok:('a -> 'c) -> error:('e -> 'c) -> ('a, 'e) t -> 'cfold ~ok ~error r is ok v if r is Ok v and error e if r is Error e.
val iter : ('a -> unit) -> ('a, 'e) t -> unititer f r is f v if r is Ok v and () otherwise.
val iter_error : ('e -> unit) -> ('a, 'e) t -> unititer_error f r is f e if r is Error e and () otherwise.
val is_ok : ('a, 'e) t -> boolis_ok (Ok _) is true, otherwise false.
val is_error : ('a, 'e) t -> boolis_error r is true iff r is Error _.
val is_bad : ('a, 'e) t -> boolSame as is_error.
val is_exn : exn -> ('a, exn) t -> boolis_exn e1 r is true iff r is Error e2 with e1=e2
equal ~ok ~error r0 r1 tests equality of r0 and r1 using ok and error to respectively compare values wrapped by Ok _ and Error _.
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.
val to_option : ('a, _) t -> 'a optionto_option r is r as an option, mapping Ok v to Some v and Error _ to None.
val of_option : 'a option -> ('a, unit) tConvert an option to a result
val to_list : ('a, 'e) t -> 'a listto_list r is [v] if r is Ok v and [] otherwise.
to_seq r is r as a sequence. Ok v is the singleton sequence containing v and Error _ is the empty sequence.
This monad is very similar to the option monad, but instead of being None when an error occurs, the first error in the sequence is preserved as the return value.
module Monad : sig ... endmodule Infix : sig ... endThis infix module provides the operator (>>=)
val print :
('b BatInnerIO.output -> 'a -> unit) ->
'b BatInnerIO.output ->
('a, exn) t ->
unitPrint a result as Ok(x) or Error(exn)