Base.Or_error
Type for tracking errors in an Error.t
. This is a specialization of the Result
type, where the Error
constructor carries an Error.t
.
A common idiom is to wrap a function that is not implemented on all platforms, e.g.,
val do_something_linux_specific : (unit -> unit) Or_error.t
Serialization and comparison of an Error
force the error's lazy message.
val hash_fold_t :
(Hash.state -> 'a -> Hash.state) ->
Hash.state ->
'a t ->
Hash.state
include Sexplib0.Sexpable.S1 with type 'a t := 'a t
val t_of_sexp : (Sexplib0.Sexp.t -> 'a) -> Sexplib0.Sexp.t -> 'a t
val sexp_of_t : ('a -> Sexplib0.Sexp.t) -> 'a t -> Sexplib0.Sexp.t
val t_sexp_grammar : 'a Sexplib0.Sexp_grammar.t -> 'a t Sexplib0.Sexp_grammar.t
Applicative
functions don't have quite the same semantics as Applicative.Of_Monad(Or_error)
would give -- apply (Error e1) (Error e2)
returns the combination of e1
and e2
, whereas it would only return e1
if it were defined using bind
.
include Applicative.S_local with type 'a t := 'a t
module Applicative_infix : sig ... end
include Invariant.S1 with type 'a t := 'a t
val invariant : ('a -> unit) -> 'a t -> unit
include Monad.S_local with type 'a t := 'a t
t >>= f
returns a computation that sequences the computations represented by two monad elements. The resulting computation first does t
to yield a value v
, and then runs the computation returned by f v
.
module Monad_infix : sig ... end
val return : 'a -> 'a t
return v
returns the (trivial) computation that returns v.
ignore_m t
is map t ~f:(fun _ -> ())
. ignore_m
used to be called ignore
, but we decided that was a bad name, because it shadowed the widely used Stdlib.ignore
. Some monads still do let ignore = ignore_m
for historical reasons.
Like all
, but ensures that every monadic value in the list produces a unit value, all of which are discarded rather than being collected into a list.
module Let_syntax : sig ... end
These are convenient to have in scope when programming with a monad:
val is_ok : _ t -> bool
val is_error : _ t -> bool
val try_with : ?backtrace:bool -> (unit -> 'a) -> 'a t
try_with f
catches exceptions thrown by f
and returns them in the Result.t
as an Error.t
. try_with_join
is like try_with
, except that f
can throw exceptions or return an Error
directly, without ending up with a nested error; it is equivalent to Result.join (try_with f)
.
val ok : 'ok t -> 'ok option
ok t
returns None
if t
is an Error
, and otherwise returns the contents of the Ok
constructor.
val ok_exn : 'a t -> 'a
ok_exn t
throws an exception if t
is an Error
, and otherwise returns the contents of the Ok
constructor.
val of_exn : ?backtrace:[ `Get | `This of string ] -> exn -> _ t
of_exn ?backtrace exn
is Error (Error.of_exn ?backtrace exn)
.
of_exn_result ?backtrace (Ok a) = Ok a
of_exn_result ?backtrace (Error exn) = of_exn ?backtrace exn
val error :
?here:Lexing.position ->
?strict:unit ->
string ->
'a ->
('a -> Sexp.t) ->
_ t
error
is a wrapper around Error.create
:
error ?strict message a sexp_of_a
= Error (Error.create ?strict message a sexp_of_a)
As with Error.create
, sexp_of_a a
is lazily computed when the info is converted to a sexp. So, if a
is mutated in the time between the call to create
and the sexp conversion, those mutations will be reflected in the sexp. Use ~strict:()
to force sexp_of_a a
to be computed immediately.
val error_string : string -> _ t
error_string message
is Error (Error.of_string message)
.
errorf format arg1 arg2 ...
is Error (sprintf format arg1 arg2 ...)
. Note that it calculates the string eagerly, so when performance matters you may want to use error
instead.
tag_arg
is like tag
, with a tag that has a sexpable argument.
val unimplemented : string -> _ t
For marking a given value as unimplemented. Typically combined with conditional compilation, where on some platforms the function is defined normally, and on some platforms it is defined as unimplemented. The supplied string should be the name of the function that is unimplemented.
val iter : 'a t -> f:('a -> unit) -> unit
combine_errors ts
returns Ok
if every element in ts
is Ok
, else it returns Error
with all the errors in ts
. More precisely:
combine_errors [Ok a1; ...; Ok an] = Ok [a1; ...; an]
combine_errors [...; Error e1; ...; Error en; ...]
= Error (Error.of_list [e1; ...; en])
combine_errors_unit ts
returns Ok
if every element in ts
is Ok ()
, else it returns Error
with all the errors in ts
, like combine_errors
.
filter_ok_at_least_one ts
returns all values in ts
that are Ok
if there is at least one, otherwise it returns the same error as combine_errors ts
.
find_ok ts
returns the first value in ts
that is Ok
, otherwise it returns the same error as combine_errors ts
.