package core_kernel

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package core_kernel
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Heap implementation based on a pairing-heap.

This heap implementations supports an arbitrary element type via a comparison function. If you need a heap with elements ordered by integers, then it may be more efficient to use a Timing_wheel.Priority_queue, which is a heap implementation specialized to integer keys, and with some other performance differences and usage restrictions.

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.

include sig ... end
val sexp_of_t : ('a -> Sexplib.Sexp.t) -> 'a t -> Sexplib.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.

val mem : 'a t -> 'a -> equal:('a -> 'a -> bool) -> bool
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
val fold_result : 'a t -> init:'accum -> f:('accum -> 'a -> ('accum, 'e) Base__.Result.t) -> ('accum, 'e) Base__.Result.t
val fold_until : 'a t -> init:'accum -> f:('accum -> 'a -> ('accum, 'stop) Base.Container_intf.Continue_or_stop.t) -> ('accum, 'stop) Base.Container_intf.Finished_or_stopped_early.t
val exists : 'a t -> f:('a -> bool) -> bool
val for_all : 'a t -> f:('a -> bool) -> bool
val count : 'a t -> f:('a -> bool) -> int
val sum : (module Base__.Commutative_group.S with type t = 'sum) -> 'a t -> f:('a -> 'sum) -> 'sum
val find : 'a t -> f:('a -> bool) -> 'a option
val find_map : 'a t -> f:('a -> 'b option) -> 'b option
val to_list : 'a t -> 'a list
val to_array : 'a t -> 'a array

Even though these two functions min_elt and max_elt are part of Container.S1, they are documented separately to make sure there is no confusion. They are independent of the comparison function used to order the heap. Instead, a traversal of the entire structure is done using the provided cmp function to find a min or max.

If you want to access the smallest element of the heap according to the heap's comparison function in constant time, you should use top.

val min_elt : 'a t -> cmp:('a -> 'a -> Base.Int.t) -> 'a Base.Option.t
val max_elt : 'a t -> cmp:('a -> 'a -> Base.Int.t) -> 'a Base.Option.t
val create : ?min_size:Base.Int.t -> cmp:('a -> 'a -> Base.Int.t) -> Base.Unit.t -> '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 Base.Array.t -> cmp:('a -> 'a -> Base.Int.t) -> 'a t

min_size (see create) will be set to the size of the input array or list.

val of_list : 'a Base.List.t -> cmp:('a -> 'a -> Base.Int.t) -> 'a t
val top : 'a t -> 'a Base.Option.t

Returns the top (i.e., smallest) element of the heap.

val top_exn : 'a t -> 'a
val add : 'a t -> 'a -> Base.Unit.t
val remove_top : _ t -> Base.Unit.t

remove_top t does nothing if t is empty.

val pop : 'a t -> 'a Base.Option.t

pop removes and returns the top (i.e. least) element.

val pop_exn : 'a t -> 'a
val pop_if : 'a t -> ('a -> Base.Bool.t) -> 'a Base.Option.t

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 -> Base.Unit.t

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 -> Base.Bool.t) -> 'a Elt.t Base.Option.t

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

Unsafe functions provide faster alternatives to regular functions with the same name. They don't allocate but the behavior is unspecified and could be memory unsafe in certain cases where regular functions would fail with informative exceptions.

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