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.

include Container.S1 with type 'a t := '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, 'stop) Base.Container_intf.Continue_or_stop.t) -> ('accum, 'stop) Base.Container_intf.Finished_or_stopped_early.t

fold_until t ~init ~f 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.

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.Commutative_group.S with type t = 'sum) -> 'a t -> f:('a -> 'sum) -> 'sum

Returns the sum of f i for 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 -> cmp:('a -> 'a -> Base.Int.t) -> 'a Base.Option.t

Even though these two functions 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 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 is surprising in two ways:

1. 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.

2. Not all the memory is freed upon remove, but rather after some number of subsequent pop operations. Alternating add and remove operations can therefore use unbounded memory.

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

This 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 Removable : sig ... end

Removable augments a heap with the ability to remove elements from the heap in lg(n) (amortized) time at any point after they have been added. Elements within a Removable heap consume 4 words more memory and all heap operations will be somewhat slower.

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