Module `Core_kernel.Heap`

Heap implementation based on a pairing-heap.

This heap implementations supports an arbitrary element type via a comparison function.

type 'a t: of_sexp and bin_io functions aren't supplied for heaps due to the difficulties in reconstructing the correct comparison function when de-serializing.

val sexp_of_t : ('a -> Ppx_sexp_conv_lib.Sexp.t) -> 'a t -> Ppx_sexp_conv_lib.Sexp.t

Mutation of the heap during iteration is not supported, but there is no check to prevent it. The behavior of a heap that is mutated during iteration is undefined.

include Container.S1 with type 'a t := 'a t

type 'a t

val mem : 'a t -> 'a -> equal:('a -> 'a -> bool) -> bool: Checks whether the provided element is there, using equal.

val length : 'a t -> int
val is_empty : 'a t -> bool
val iter : 'a t -> f:('a -> unit) -> unit
val fold : 'a t -> init:'accum -> f:('accum -> 'a -> 'accum) -> 'accum: fold t ~init ~f returns f (... f (f (f init e1) e2) e3 ...) en, where e1..en are the elements of t

val fold_result : 'a t -> init:'accum -> f:('accum -> 'a -> ('accum, 'e) Base.Result.t) -> ('accum, 'e) Base.Result.t: fold_result t ~init ~f is a short-circuiting version of fold that runs in the Result monad. If f returns an Error _, that value is returned without any additional invocations of f.

val fold_until : 'a t -> init:'accum -> f:('accum -> 'a -> ('accum, 'final) Base__.Container_intf.Continue_or_stop.t) -> finish:('accum -> 'final) -> 'final

fold_until t ~init ~f ~finish is a short-circuiting version of fold. If f returns Stop _ the computation ceases and results in that value. If f returns Continue _, the fold will proceed. If f never returns Stop _, the final result is computed by finish.

Example:

type maybe_negative =
  | Found_negative of int
  | All_nonnegative of { sum : int }

(** [first_neg_or_sum list] returns the first negative number in [list], if any,
    otherwise returns the sum of the list. *)
let first_neg_or_sum =
  List.fold_until ~init:0
    ~f:(fun sum x ->
      if x < 0
      then Stop (Found_negative x)
      else Continue (sum + x))
    ~finish:(fun sum -> All_nonnegative { sum })
;;

let x = first_neg_or_sum [1; 2; 3; 4; 5]
val x : maybe_negative = All_nonnegative {sum = 15}

let y = first_neg_or_sum [1; 2; -3; 4; 5]
val y : maybe_negative = Found_negative -3

val exists : 'a t -> f:('a -> bool) -> bool: Returns true if and only if there exists an element for which the provided function evaluates to true. This is a short-circuiting operation.

val for_all : 'a t -> f:('a -> bool) -> bool: Returns true if and only if the provided function evaluates to true for all elements. This is a short-circuiting operation.

val count : 'a t -> f:('a -> bool) -> int: Returns the number of elements for which the provided function evaluates to true.

val sum : (module Base__.Container_intf.Summable with type t = 'sum) -> 'a t -> f:('a -> 'sum) -> 'sum: Returns the sum of f i for all i in the container.

val find : 'a t -> f:('a -> bool) -> 'a option: Returns as an option the first element for which f evaluates to true.

val find_map : 'a t -> f:('a -> 'b option) -> 'b option: Returns the first evaluation of f that returns Some, and returns None if there is no such element.

val to_list : 'a t -> 'a list
val to_array : 'a t -> 'a array
val min_elt : 'a t -> compare:('a -> 'a -> int) -> 'a option: Returns a minimum (resp maximum) element from the collection using the provided compare function, or None if the collection is empty. In case of a tie, the first element encountered while traversing the collection is returned. The implementation uses fold so it has the same complexity as fold.

val max_elt : 'a t -> compare:('a -> 'a -> int) -> 'a option

include Core_kernel__.Import.Invariant.S1 with type 'a t := 'a t

type 'a t

val invariant : 'a Base__.Invariant_intf.inv -> 'a t Base__.Invariant_intf.inv

val min_elt : 'a t -> compare:('a -> 'a -> Core_kernel__.Import.int) -> 'a Core_kernel__.Import.option

val max_elt : 'a t -> compare:('a -> 'a -> Core_kernel__.Import.int) -> 'a Core_kernel__.Import.option

val create : ?⁠min_size:Core_kernel__.Import.int -> cmp:('a -> 'a -> Core_kernel__.Import.int) -> Core_kernel__.Import.unit -> 'a t

create ?min_size ~cmp returns a new min-heap that can store min_size elements without reallocations, using ordering function cmp.

The top of the heap is the smallest element as determined by the provided comparison function. In particular, if cmp x y < 0 then x will be "on top of" y in the heap.

Memory use can be surprising in that the underlying pool never shrinks, so current memory use will at least be proportional to the largest number of elements that the heap has ever held.

val of_array : 'a Core_kernel__.Import.array -> cmp:('a -> 'a -> Core_kernel__.Import.int) -> 'a t: min_size (see create) will be set to the size of the input array or list.

val of_list : 'a Core_kernel__.Import.list -> cmp:('a -> 'a -> Core_kernel__.Import.int) -> 'a t
val top : 'a t -> 'a Core_kernel__.Import.option: Returns the top (i.e., smallest) element of the heap.

val top_exn : 'a t -> 'a
val add : 'a t -> 'a -> Core_kernel__.Import.unit
val remove_top : _ t -> Core_kernel__.Import.unit: remove_top t does nothing if t is empty.

val pop : 'a t -> 'a Core_kernel__.Import.option: pop removes and returns the top (i.e. least) element.

val pop_exn : 'a t -> 'a
val pop_if : 'a t -> ('a -> Core_kernel__.Import.bool) -> 'a Core_kernel__.Import.option: pop_if t cond returns Some top_element of t if it satisfies condition cond, removing it, or None in any other case.

val copy : 'a t -> 'a t: copy t returns a shallow copy.

module Elt : sig ... end

val add_removable : 'a t -> 'a -> 'a Elt.t

add_removable t v adds v to t, returning a token that can be used to delete v from t in lg(n) amortized time.

Note that while add doesn't allocate unless the underlying pool needs to be resized, add_removable always allocates. The Unsafe module has a non-allocating alternative.

val remove : 'a t -> 'a Elt.t -> Core_kernel__.Import.unit: If t and token are mismatched then behavior is undefined. Trying to remove an already removed token (by an earlier call to remove or pop for instance) is a no-op, but keeping token around after it has been removed may lead to memory leaks since it has a reference to the heap.

val update : 'a t -> 'a Elt.t -> 'a -> 'a Elt.t: update t token v is shorthand for remove t token; add_removable t v.

val find_elt : 'a t -> f:('a -> Core_kernel__.Import.bool) -> 'a Elt.t Core_kernel__.Import.option: find_elt t ~f. If f is true for some element in t, return an Elt.t for that element. This operation is O(n).

module Unsafe : sig ... end