(* This file is free software, part of containers. See file "license" for more details. *)

open CCShims_

type t = float
type fpclass = Stdlib.fpclass =
  | FP_normal
  | FP_subnormal
  | FP_zero
  | FP_infinite
  | FP_nan

module Infix = struct
  let (=) : t -> t -> bool = Stdlib.(=)
  let (<>) : t -> t -> bool = Stdlib.(<>)
  let (<) : t -> t -> bool = Stdlib.(<)
  let (>) : t -> t -> bool = Stdlib.(>)
  let (<=) : t -> t -> bool = Stdlib.(<=)
  let (>=) : t -> t -> bool = Stdlib.(>=)
  let (~-) : t -> t = Stdlib.(~-.)
  let (+) : t -> t -> t = Stdlib.(+.)
  let (-) : t -> t -> t = Stdlib.(-.)
  let ( * ) : t -> t -> t = Stdlib.( *. )
  let (/) : t -> t -> t = Stdlib.(/.)
end
include Infix

let nan = Stdlib.nan

let infinity = Stdlib.infinity
let neg_infinity = Stdlib.neg_infinity

let max_value = infinity
let min_value = neg_infinity

let max_finite_value = Stdlib.max_float

let epsilon = Stdlib.epsilon_float

let pi = 0x1.921fb54442d18p+1

let is_nan x = Stdlib.(classify_float x = Stdlib.FP_nan)

let add = (+.)
let sub = (-.)
let mul = ( *. )
let div = (/.)
let neg = (~-.)
let abs = Stdlib.abs_float
let scale = ( *. )

let min (x : t) y =
  match Stdlib.classify_float x, Stdlib.classify_float y with
    | FP_nan, _ -> y
    | _, FP_nan -> x
    | _ -> if x < y then x else y

let max (x : t) y =
  match Stdlib.classify_float x, Stdlib.classify_float y with
    | FP_nan, _ -> y
    | _, FP_nan -> x
    | _ -> if x > y then x else y

(*$T
  max nan 1. = 1.
  min nan 1. = 1.
  max 1. nan = 1.
  min 1. nan = 1.
*)

(*$Q
  Q.(pair float float) (fun (x,y) -> \
    is_nan x || is_nan y || (min x y <= x && min x y <= y))
  Q.(pair float float) (fun (x,y) -> \
    is_nan x || is_nan y || (max x y >= x && max x y >= y))
  *)

let equal (a:float) b = a=b

let hash : t -> int = Hashtbl.hash
let compare (a:float) b = Stdlib.compare a b

type 'a printer = Format.formatter -> 'a -> unit
type 'a random_gen = Random.State.t -> 'a

let pp = Format.pp_print_float

let fsign a =
  if is_nan a then nan
  else if a = 0. then a
  else Stdlib.copysign 1. a

exception TrapNaN of string

let sign_exn (a:float) =
  if is_nan a then raise (TrapNaN "sign_exn")
  else compare a 0.

let round x =
  let low = floor x in
  let high = ceil x in
  if x-.low > high-.x then high else low

(*$=
  2. (round 1.6)
  1. (round 1.4)
  0. (round 0.)
*)

let to_int (a:float) = Stdlib.int_of_float a
let of_int (a:int) = Stdlib.float_of_int a

let to_string (a:float) = Stdlib.string_of_float a
let of_string_exn (a:string) = Stdlib.float_of_string a
let of_string_opt (a:string) =
  try Some (Stdlib.float_of_string a)
  with Failure _ -> None


let random n st = Random.State.float st n
let random_small = random 100.0
let random_range i j st = i +. random (j-.i) st

let equal_precision ~epsilon a b = abs_float (a-.b) < epsilon

let classify = Stdlib.classify_float