package tezos-lwt-result-stdlib

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package tezos-lwt-result-stdlib
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Parameters

Signature

include Bare_sigs.List.S

Trivial values

type 'a t = 'a List.t =
  1. | []
  2. | :: of 'a * 'a list

in-monad, preallocated nil

val nil : 'a list

nil is []

val nil_e : ('a list, 'trace) result

nil is Ok []

val nil_s : 'a list Lwt.t

nil is Lwt.return_nil

val nil_es : ('a list, 'trace) result Lwt.t

nil is Lwt.return (Ok [])

Safe wrappers

Shadowing unsafe functions to avoid all exceptions.

Safe lookups, scans, retrievals

Return option rather than raise Not_found, Failure _, or Invalid_argument _

val hd : 'a list -> 'a option

hd xs is the head (first element) of the list or None if the list is empty.

val tl : 'a list -> 'a list option

tl xs is the tail of the list (the whole list except the first element) or None if the list is empty.

val nth : 'a list -> int -> 'a option

nth xs n is the nth element of the list or None if the list has fewer than n elements.

nth xs 0 = tl xs

val nth_opt : 'a list -> int -> 'a option

nth_opt is an alias for nth provided for backwards compatibility.

val last : 'a -> 'a list -> 'a

last x xs is the last element of the list xs or x if xs is empty.

The primary intended use for last is after destructing a list: match l with | None -> … | Some x :: xs -> last x xs but it can also be used for a default value: last default_value_if_empty xs.

val last_opt : 'a list -> 'a option

last_opt xs is the last element of the list xs or None if the list xs is empty.

val find : ('a -> bool) -> 'a list -> 'a option

find predicate xs is the first element x of the list xs such that predicate x is true or None if the list xs has no such element.

val find_opt : ('a -> bool) -> 'a list -> 'a option

find_opt is an alias for find provided for backwards compatibility.

val mem : equal:('a -> 'a -> bool) -> 'a -> 'a list -> bool

mem ~equal a l is true iff there is an element e of l such that equal a e.

val assoc : equal:('a -> 'a -> bool) -> 'a -> ('a * 'b) list -> 'b option

assoc ~equal k kvs is Some v such that (k', v) is the first pair in the list such that equal k' k or None if the list contains no such pair.

val assoc_opt : equal:('a -> 'a -> bool) -> 'a -> ('a * 'b) list -> 'b option

assoc_opt is an alias for assoc provided for backwards compatibility.

val assq : 'a -> ('a * 'b) list -> 'b option

assq k kvs is the same as assoc ~equal:Stdlib.( == ) k kvs: it uses the physical equality.

val assq_opt : 'a -> ('a * 'b) list -> 'b option

assq_opt is an alias for assq provided for backwards compatibility.

val mem_assoc : equal:('a -> 'a -> bool) -> 'a -> ('a * 'b) list -> bool

mem_assoc ~equal k l is equivalent to Option.is_some @@ assoc ~equal k l.

val mem_assq : 'a -> ('a * 'b) list -> bool

mem_assq k l is mem_assoc ~equal:Stdlib.( == ) k l.

val remove_assoc : equal:('a -> 'a -> bool) -> 'a -> ('a * 'b) list -> ('a * 'b) list

remove_assoc ~equal k l is l without the first element (k', _) such that equal k k'.

val remove_assq : 'a -> ('a * 'b) list -> ('a * 'b) list

remove_assoq k l is remove_assoc ~equal:Stdlib.( == ) k l.

Initialisation
val init : when_negative_length:'trace -> int -> (int -> 'a) -> ('a list, 'trace) result

init ~when_negative_length n f is Error when_negative_length if n is strictly negative and Ok (Stdlib.List.init n f) otherwise.

Basic traversal
val length : 'a list -> int
val rev : 'a list -> 'a list
val concat : 'a list list -> 'a list
val append : 'a list -> 'a list -> 'a list
val rev_append : 'a list -> 'a list -> 'a list
val flatten : 'a list list -> 'a list
Double-list traversals

These safe-wrappers take an explicit value to handle the case of lists of unequal length.

val combine : when_different_lengths:'trace -> 'a list -> 'b list -> (('a * 'b) list, 'trace) result

combine ~when_different_lengths l1 l2 is either

  • Error when_different_lengths if List.length l1 <> List.length l2
  • a list of pairs of elements from l1 and l2

E.g., combine ~when_different_lengths [] [] = Ok []

E.g., combine ~when_different_lengths [1; 2] ['a'; 'b'] = Ok [(1,'a'); (2, 'b')]

E.g., combine ~when_different_lengths:() [1] [] = Error ()

Note: combine ~when_different_lengths l1 l2 is equivalent to try Ok (Stdlib.List.combine l1 l2) with Invalid_argument _ -> when_different_lengths

The same equivalence almost holds for the other double traversors below. The notable difference is if the functions passed as argument to the traversors raise the Invalid_argument _ exception.

val rev_combine : when_different_lengths:'trace -> 'a list -> 'b list -> (('a * 'b) list, 'trace) result

rev_combine ~when_different_lengths xs ys is rev (combine ~when_different_lengths xs ys) but more efficient.

val split : ('a * 'b) list -> 'a list * 'b list
val iter2 : when_different_lengths:'trace -> ('a -> 'b -> unit) -> 'a list -> 'b list -> (unit, 'trace) result
val map2 : when_different_lengths:'trace -> ('a -> 'b -> 'c) -> 'a list -> 'b list -> ('c list, 'trace) result
val rev_map2 : when_different_lengths:'trace -> ('a -> 'b -> 'c) -> 'a list -> 'b list -> ('c list, 'trace) result
val fold_left2 : when_different_lengths:'trace -> ('a -> 'b -> 'c -> 'a) -> 'a -> 'b list -> 'c list -> ('a, 'trace) result
val fold_right2 : when_different_lengths:'trace -> ('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> 'c -> ('c, 'trace) result

This function is not tail-recursive

val for_all2 : when_different_lengths:'trace -> ('a -> 'b -> bool) -> 'a list -> 'b list -> (bool, 'trace) result
val exists2 : when_different_lengths:'trace -> ('a -> 'b -> bool) -> 'a list -> 'b list -> (bool, 'trace) result

Monad-aware variants

The functions below are strict extensions of the standard Stdlib.List module. It is for result-, lwt- and lwt-result-aware variants. The meaning of the suffix is as described above, in Lwtreslib, and in Sigs.Seq.

Initialisation variants

Note that for asynchronous variants (_s, _es, _p, and _ep), if the length parameter is negative, then the promise is returned already fulfilled with Error when_different_lengths.

val init_e : when_negative_length:'trace -> int -> (int -> ('a, 'trace) result) -> ('a list, 'trace) result
val init_s : when_negative_length:'trace -> int -> (int -> 'a Lwt.t) -> ('a list, 'trace) result Lwt.t
val init_es : when_negative_length:'trace -> int -> (int -> ('a, 'trace) result Lwt.t) -> ('a list, 'trace) result Lwt.t
val init_p : when_negative_length:'trace -> int -> (int -> 'a Lwt.t) -> ('a list, 'trace) result Lwt.t
Query variants
val find_e : ('a -> (bool, 'trace) result) -> 'a list -> ('a option, 'trace) result
val find_s : ('a -> bool Lwt.t) -> 'a list -> 'a option Lwt.t
val find_es : ('a -> (bool, 'trace) result Lwt.t) -> 'a list -> ('a option, 'trace) result Lwt.t
val filter : ('a -> bool) -> 'a list -> 'a list
val rev_filter : ('a -> bool) -> 'a list -> 'a list

rev_filter f l is rev (filter f l) but more efficient.

val rev_filter_some : 'a option list -> 'a list
val filter_some : 'a option list -> 'a list
val rev_filter_ok : ('a, 'b) result list -> 'a list
val filter_ok : ('a, 'b) result list -> 'a list
val rev_filter_error : ('a, 'b) result list -> 'b list
val filter_error : ('a, 'b) result list -> 'b list
val rev_filter_e : ('a -> (bool, 'trace) result) -> 'a list -> ('a list, 'trace) result
val filter_e : ('a -> (bool, 'trace) result) -> 'a list -> ('a list, 'trace) result
val rev_filter_s : ('a -> bool Lwt.t) -> 'a list -> 'a list Lwt.t
val filter_s : ('a -> bool Lwt.t) -> 'a list -> 'a list Lwt.t
val rev_filter_es : ('a -> (bool, 'trace) result Lwt.t) -> 'a list -> ('a list, 'trace) result Lwt.t
val filter_es : ('a -> (bool, 'trace) result Lwt.t) -> 'a list -> ('a list, 'trace) result Lwt.t
val filter_p : ('a -> bool Lwt.t) -> 'a list -> 'a list Lwt.t
val rev_partition : ('a -> bool) -> 'a list -> 'a list * 'a list
val partition : ('a -> bool) -> 'a list -> 'a list * 'a list
val rev_partition_result : ('a, 'b) result list -> 'a list * 'b list
val partition_result : ('a, 'b) result list -> 'a list * 'b list
val rev_partition_e : ('a -> (bool, 'trace) result) -> 'a list -> ('a list * 'a list, 'trace) result
val partition_e : ('a -> (bool, 'trace) result) -> 'a list -> ('a list * 'a list, 'trace) result
val rev_partition_s : ('a -> bool Lwt.t) -> 'a list -> ('a list * 'a list) Lwt.t
val partition_s : ('a -> bool Lwt.t) -> 'a list -> ('a list * 'a list) Lwt.t
val rev_partition_es : ('a -> (bool, 'trace) result Lwt.t) -> 'a list -> ('a list * 'a list, 'trace) result Lwt.t
val partition_es : ('a -> (bool, 'trace) result Lwt.t) -> 'a list -> ('a list * 'a list, 'trace) result Lwt.t
val partition_p : ('a -> bool Lwt.t) -> 'a list -> ('a list * 'a list) Lwt.t
val iter : ('a -> unit) -> 'a list -> unit

Traversal variants

val iter_e : ('a -> (unit, 'trace) result) -> 'a list -> (unit, 'trace) result
val iter_s : ('a -> unit Lwt.t) -> 'a list -> unit Lwt.t
val iter_es : ('a -> (unit, 'trace) result Lwt.t) -> 'a list -> (unit, 'trace) result Lwt.t
val iter_p : ('a -> unit Lwt.t) -> 'a list -> unit Lwt.t
val iteri : (int -> 'a -> unit) -> 'a list -> unit
val iteri_e : (int -> 'a -> (unit, 'trace) result) -> 'a list -> (unit, 'trace) result
val iteri_s : (int -> 'a -> unit Lwt.t) -> 'a list -> unit Lwt.t
val iteri_es : (int -> 'a -> (unit, 'trace) result Lwt.t) -> 'a list -> (unit, 'trace) result Lwt.t
val iteri_p : (int -> 'a -> unit Lwt.t) -> 'a list -> unit Lwt.t
val map : ('a -> 'b) -> 'a list -> 'b list
val map_e : ('a -> ('b, 'trace) result) -> 'a list -> ('b list, 'trace) result
val map_s : ('a -> 'b Lwt.t) -> 'a list -> 'b list Lwt.t
val map_es : ('a -> ('b, 'trace) result Lwt.t) -> 'a list -> ('b list, 'trace) result Lwt.t
val map_p : ('a -> 'b Lwt.t) -> 'a list -> 'b list Lwt.t
val mapi : (int -> 'a -> 'b) -> 'a list -> 'b list
val mapi_e : (int -> 'a -> ('b, 'trace) result) -> 'a list -> ('b list, 'trace) result
val mapi_s : (int -> 'a -> 'b Lwt.t) -> 'a list -> 'b list Lwt.t
val mapi_es : (int -> 'a -> ('b, 'trace) result Lwt.t) -> 'a list -> ('b list, 'trace) result Lwt.t
val mapi_p : (int -> 'a -> 'b Lwt.t) -> 'a list -> 'b list Lwt.t
val rev_map : ('a -> 'b) -> 'a list -> 'b list
val rev_mapi : (int -> 'a -> 'b) -> 'a list -> 'b list
val rev_map_e : ('a -> ('b, 'trace) result) -> 'a list -> ('b list, 'trace) result
val rev_map_s : ('a -> 'b Lwt.t) -> 'a list -> 'b list Lwt.t
val rev_map_es : ('a -> ('b, 'trace) result Lwt.t) -> 'a list -> ('b list, 'trace) result Lwt.t
val rev_map_p : ('a -> 'b Lwt.t) -> 'a list -> 'b list Lwt.t
val rev_mapi_e : (int -> 'a -> ('b, 'trace) result) -> 'a list -> ('b list, 'trace) result
val rev_mapi_s : (int -> 'a -> 'b Lwt.t) -> 'a list -> 'b list Lwt.t
val rev_mapi_es : (int -> 'a -> ('b, 'trace) result Lwt.t) -> 'a list -> ('b list, 'trace) result Lwt.t
val rev_mapi_p : (int -> 'a -> 'b Lwt.t) -> 'a list -> 'b list Lwt.t
val rev_filter_map : ('a -> 'b option) -> 'a list -> 'b list
val rev_filter_map_e : ('a -> ('b option, 'trace) result) -> 'a list -> ('b list, 'trace) result
val filter_map_e : ('a -> ('b option, 'trace) result) -> 'a list -> ('b list, 'trace) result
val rev_filter_map_s : ('a -> 'b option Lwt.t) -> 'a list -> 'b list Lwt.t
val filter_map : ('a -> 'b option) -> 'a list -> 'b list
val filter_map_s : ('a -> 'b option Lwt.t) -> 'a list -> 'b list Lwt.t
val rev_filter_map_es : ('a -> ('b option, 'trace) result Lwt.t) -> 'a list -> ('b list, 'trace) result Lwt.t
val filter_map_es : ('a -> ('b option, 'trace) result Lwt.t) -> 'a list -> ('b list, 'trace) result Lwt.t
val filter_map_p : ('a -> 'b option Lwt.t) -> 'a list -> 'b list Lwt.t
val fold_left : ('a -> 'b -> 'a) -> 'a -> 'b list -> 'a
val fold_left_e : ('a -> 'b -> ('a, 'trace) result) -> 'a -> 'b list -> ('a, 'trace) result
val fold_left_s : ('a -> 'b -> 'a Lwt.t) -> 'a -> 'b list -> 'a Lwt.t
val fold_left_es : ('a -> 'b -> ('a, 'trace) result Lwt.t) -> 'a -> 'b list -> ('a, 'trace) result Lwt.t
val fold_right : ('a -> 'b -> 'b) -> 'a list -> 'b -> 'b

This function is not tail-recursive

val fold_right_e : ('a -> 'b -> ('b, 'trace) result) -> 'a list -> 'b -> ('b, 'trace) result

This function is not tail-recursive

val fold_right_s : ('a -> 'b -> 'b Lwt.t) -> 'a list -> 'b -> 'b Lwt.t

This function is not tail-recursive

val fold_right_es : ('a -> 'b -> ('b, 'trace) result Lwt.t) -> 'a list -> 'b -> ('b, 'trace) result Lwt.t

This function is not tail-recursive

Double-traversal variants

As mentioned above, there are no _p and _ep double-traversors. Use combine (and variants) to circumvent this.

val iter2_e : when_different_lengths:'trace -> ('a -> 'b -> (unit, 'trace) result) -> 'a list -> 'b list -> (unit, 'trace) result
val iter2_s : when_different_lengths:'trace -> ('a -> 'b -> unit Lwt.t) -> 'a list -> 'b list -> (unit, 'trace) result Lwt.t
val iter2_es : when_different_lengths:'trace -> ('a -> 'b -> (unit, 'trace) result Lwt.t) -> 'a list -> 'b list -> (unit, 'trace) result Lwt.t
val map2_e : when_different_lengths:'trace -> ('a -> 'b -> ('c, 'trace) result) -> 'a list -> 'b list -> ('c list, 'trace) result
val map2_s : when_different_lengths:'trace -> ('a -> 'b -> 'c Lwt.t) -> 'a list -> 'b list -> ('c list, 'trace) result Lwt.t
val map2_es : when_different_lengths:'trace -> ('a -> 'b -> ('c, 'trace) result Lwt.t) -> 'a list -> 'b list -> ('c list, 'trace) result Lwt.t
val rev_map2_e : when_different_lengths:'trace -> ('a -> 'b -> ('c, 'trace) result) -> 'a list -> 'b list -> ('c list, 'trace) result
val rev_map2_s : when_different_lengths:'trace -> ('a -> 'b -> 'c Lwt.t) -> 'a list -> 'b list -> ('c list, 'trace) result Lwt.t
val rev_map2_es : when_different_lengths:'trace -> ('a -> 'b -> ('c, 'trace) result Lwt.t) -> 'a list -> 'b list -> ('c list, 'trace) result Lwt.t
val fold_left2_e : when_different_lengths:'trace -> ('a -> 'b -> 'c -> ('a, 'trace) result) -> 'a -> 'b list -> 'c list -> ('a, 'trace) result
val fold_left2_s : when_different_lengths:'trace -> ('a -> 'b -> 'c -> 'a Lwt.t) -> 'a -> 'b list -> 'c list -> ('a, 'trace) result Lwt.t
val fold_left2_es : when_different_lengths:'trace -> ('a -> 'b -> 'c -> ('a, 'trace) result Lwt.t) -> 'a -> 'b list -> 'c list -> ('a, 'trace) result Lwt.t
val fold_right2_e : when_different_lengths:'trace -> ('a -> 'b -> 'c -> ('c, 'trace) result) -> 'a list -> 'b list -> 'c -> ('c, 'trace) result

This function is not tail-recursive

val fold_right2_s : when_different_lengths:'trace -> ('a -> 'b -> 'c -> 'c Lwt.t) -> 'a list -> 'b list -> 'c -> ('c, 'trace) result Lwt.t

This function is not tail-recursive

val fold_right2_es : when_different_lengths:'trace -> ('a -> 'b -> 'c -> ('c, 'trace) result Lwt.t) -> 'a list -> 'b list -> 'c -> ('c, 'trace) result Lwt.t

This function is not tail-recursive

Scanning variants
val for_all : ('a -> bool) -> 'a list -> bool
val for_all_e : ('a -> (bool, 'trace) result) -> 'a list -> (bool, 'trace) result
val for_all_s : ('a -> bool Lwt.t) -> 'a list -> bool Lwt.t
val for_all_es : ('a -> (bool, 'trace) result Lwt.t) -> 'a list -> (bool, 'trace) result Lwt.t
val for_all_p : ('a -> bool Lwt.t) -> 'a list -> bool Lwt.t
val exists : ('a -> bool) -> 'a list -> bool
val exists_e : ('a -> (bool, 'trace) result) -> 'a list -> (bool, 'trace) result
val exists_s : ('a -> bool Lwt.t) -> 'a list -> bool Lwt.t
val exists_es : ('a -> (bool, 'trace) result Lwt.t) -> 'a list -> (bool, 'trace) result Lwt.t
val exists_p : ('a -> bool Lwt.t) -> 'a list -> bool Lwt.t
Double-scanning variants

As mentioned above, there are no _p and _ep double-scanners. Use combine (and variants) to circumvent this.

val for_all2_e : when_different_lengths:'trace -> ('a -> 'b -> (bool, 'trace) result) -> 'a list -> 'b list -> (bool, 'trace) result
val for_all2_s : when_different_lengths:'trace -> ('a -> 'b -> bool Lwt.t) -> 'a list -> 'b list -> (bool, 'trace) result Lwt.t
val for_all2_es : when_different_lengths:'trace -> ('a -> 'b -> (bool, 'trace) result Lwt.t) -> 'a list -> 'b list -> (bool, 'trace) result Lwt.t
val exists2_e : when_different_lengths:'trace -> ('a -> 'b -> (bool, 'trace) result) -> 'a list -> 'b list -> (bool, 'trace) result
val exists2_s : when_different_lengths:'trace -> ('a -> 'b -> bool Lwt.t) -> 'a list -> 'b list -> (bool, 'trace) result Lwt.t
val exists2_es : when_different_lengths:'trace -> ('a -> 'b -> (bool, 'trace) result Lwt.t) -> 'a list -> 'b list -> (bool, 'trace) result Lwt.t

Combine variants

These are primarily intended to be used for preprocessing before applying a traversor to the resulting list of pairs. They give alternatives to the when_different_lengths mechanism of the immediate double-traversors above.

In case the semantic of, say, map2_es was unsatisfying, one can use map_es on a combine-preprocessed pair of lists. The different variants of combine give different approaches to different-length handling.

val combine_drop : 'a list -> 'b list -> ('a * 'b) list

combine_drop ll lr is a list l of pairs of elements taken from the common-length prefix of ll and lr. The suffix of whichever list is longer (if any) is dropped.

More formally nth l n is:

  • None if n >= min (length ll) (length lr)
  • Some (Option.get @@ nth ll n, Option.get @@ nth lr n) otherwise
val combine_with_leftovers : 'a list -> 'b list -> ('a * 'b) list * [ `Left of 'a list | `Right of 'b list ] option

combine_with_leftovers ll lr is a tuple (combined, leftover) where combined is combine_drop ll lr and leftover is either `Left lsuffix or `Right rsuffix depending on which of ll or lr is longer. leftover is None if the two lists have the same length.

compare / equal

val compare : ('a -> 'a -> int) -> 'a list -> 'a list -> int
val equal : ('a -> 'a -> bool) -> 'a list -> 'a list -> bool

Sorting

val sort : ('a -> 'a -> int) -> 'a list -> 'a list
val stable_sort : ('a -> 'a -> int) -> 'a list -> 'a list
val fast_sort : ('a -> 'a -> int) -> 'a list -> 'a list
val sort_uniq : ('a -> 'a -> int) -> 'a list -> 'a list

conversion

val to_seq : 'a t -> 'a Seq.t
val of_seq : 'a Seq.t -> 'a list
val init_ep : when_negative_length:'error -> int -> (int -> ('a, 'error Monad.trace) result Lwt.t) -> ('a list, 'error Monad.trace) result Lwt.t
val filter_ep : ('a -> (bool, 'error Monad.trace) result Lwt.t) -> 'a list -> ('a list, 'error Monad.trace) result Lwt.t
val partition_ep : ('a -> (bool, 'error Monad.trace) result Lwt.t) -> 'a list -> ('a list * 'a list, 'error Monad.trace) result Lwt.t
val iter_ep : ('a -> (unit, 'error Monad.trace) result Lwt.t) -> 'a list -> (unit, 'error Monad.trace) result Lwt.t
val iteri_ep : (int -> 'a -> (unit, 'error Monad.trace) result Lwt.t) -> 'a list -> (unit, 'error Monad.trace) result Lwt.t
val map_ep : ('a -> ('b, 'error Monad.trace) result Lwt.t) -> 'a list -> ('b list, 'error Monad.trace) result Lwt.t
val mapi_ep : (int -> 'a -> ('b, 'error Monad.trace) result Lwt.t) -> 'a list -> ('b list, 'error Monad.trace) result Lwt.t
val rev_map_ep : ('a -> ('b, 'error Monad.trace) result Lwt.t) -> 'a list -> ('b list, 'error Monad.trace) result Lwt.t
val rev_mapi_ep : (int -> 'a -> ('b, 'error Monad.trace) result Lwt.t) -> 'a list -> ('b list, 'error Monad.trace) result Lwt.t
val filter_map_ep : ('a -> ('b option, 'error Monad.trace) result Lwt.t) -> 'a list -> ('b list, 'error Monad.trace) result Lwt.t
val for_all_ep : ('a -> (bool, 'error Monad.trace) result Lwt.t) -> 'a list -> (bool, 'error Monad.trace) result Lwt.t
val exists_ep : ('a -> (bool, 'error Monad.trace) result Lwt.t) -> 'a list -> (bool, 'error Monad.trace) result Lwt.t
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