52 lines
1.5 KiB
OCaml
52 lines
1.5 KiB
OCaml
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(** Element ordering *)
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type t =
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| Lt (** Lesser than *)
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| Eq (** Equal *)
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| Gt (** Greater than *)
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val of_int : int -> t
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val to_int : t -> int
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(** returns the string representation. one of: "<", "=", ">" *)
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val to_string : t -> string
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val is_eq : t -> bool
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val min : ('a -> 'a -> t) -> 'a -> 'a -> 'a
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val max : ('a -> 'a -> t) -> 'a -> 'a -> 'a
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(** [reverse cmp] takes a comparison function [cmp] and returns a new comparison
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function whose comparisons are the opposite of that of [cmp]. *)
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val reverse : ('a -> 'a -> t) -> 'a -> 'a -> t
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module O : sig
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(** A convenient operator for efficiently chaining multiple comparisons
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together. For example, you can write
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{v
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let compare { x; y; z } t =
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let open Ordering.O in
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let= () = compare_x x t.x in
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let= () = compare_y y t.y in
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compare_z z t.z
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v}
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or, a bit less compactly but more symmetrically
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{v
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let compare { x; y; z } t =
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let open Ordering.O in
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let= () = compare_x x t.x in
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let= () = compare_y y t.y in
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let= () = compare_z z t.z in
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Eq
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v}
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to chain three comparisons instead of the usual triply nested [match].
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Note that the resulting code can be up to 2x slower than nested [match]ing
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due to extra allocations that we are unable to eliminate (as of Nov 2021),
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so you should use [let=] only where appropriate. *)
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val ( let= ) : t -> (unit -> t) -> t
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end
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