package interval_base

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Module type Interval.TSource

Basic signature for interval arithmetic packages.

Sourcetype number

Numbers type on which intervals are defined.

Sourcetype t

The type of intervals.

Sourceval zero : t

Neutral element for addition.

Sourceval one : t

Neutral element for multiplication.

Sourceval pi : t

π with bounds properly rounded.

Sourceval two_pi : t

2π with bounds properly rounded.

Sourceval half_pi : t

π/2 with bounds properly rounded.

Sourceval e : t

e (Euler's constant) with bounds properly rounded.

Sourceval entire : t

The entire set of numbers.

  • since 1.5
Sourceval v : number -> number -> t

v a b returns the interval [a, b]. BEWARE that, unless you take care, if you use v a b with literal values for a and/or b, the resulting interval may not contain these values because the compiler will round them to binary numbers before passing them to v.

  • raises Invalid_argument

    if the interval [a, b] is equal to [-∞,-∞] or [+∞,+∞] or one of the bounds is NaN.

Sourceval low : t -> number

low t returns the lower bound of the interval.

Sourceval high : t -> number

high t returns the higher bound of the interval.

Sourceval of_int : int -> t

Returns the interval containing the conversion of an integer to the number type.

Sourceval to_string : ?fmt:(number -> 'b, 'a, 'b) format -> t -> string

to_string i return a string representation of the interval i.

  • parameter fmt

    is the format used to print the two bounds of i. Default: "%g" for float numbers.

Sourceval pr : out_channel -> t -> unit

Print the interval to the channel. To be used with Printf format "%a".

Sourceval pp : Format.formatter -> t -> unit

Print the interval to the formatter. To be used with Format format "%a".

Sourceval fmt : (number -> 'b, 'a, 'b) format -> (t -> 'c, 'd, 'e, 'c) format4

fmt number_fmt returns a format to print intervals where each component is printed with number_fmt.

Example: Printf.printf ("%s = " ^^ fmt "%.10f" ^^ "\n") name i.

Boolean functions

Sourceval compare_f : t -> number -> int

compare_f a x returns

  • 1 if high(a) < x,
  • 0 if low(a) ≤ x ≤ high(a), i.e., if x ∈ a, and
  • -1 if x < low(a).
Sourceval is_bounded : t -> bool

is_bounded x says whether the interval is bounded, i.e., -∞ < low(x) and high(x) < ∞.

  • since 1.5
Sourceval is_entire : t -> bool

is_entire x says whether x is the entire interval.

  • since 1.5
Sourceval equal : t -> t -> bool

equal a b says whether the two intervals are the same.

  • since 1.5
Sourceval (=) : t -> t -> bool

Synonym for equal.

  • since 1.5
Sourceval subset : t -> t -> bool

subset x y returns true iff x ⊆ y.

  • since 1.5
Sourceval (<=) : t -> t -> bool

x <= y says whether x is weakly less than y i.e., ∀ξ ∈ x, ∃η ∈ y, ξ ≤ η and ∀η ∈ y, ∃ξ ∈ x, ξ ≤ η.

  • since 1.5
Sourceval (>=) : t -> t -> bool

x >= y says whether x is weakly greater than y i.e., ∀ξ ∈ x, ∃η ∈ y, ξ ≥ η and ∀η ∈ y, ∃ξ ∈ x, ξ ≥ η.

  • since 1.5
Sourceval precedes : t -> t -> bool

precedes x y returns true iff x is to the left but may touch y.

  • since 1.5
Sourceval interior : t -> t -> bool

interior x y returns true if x is interior to y in the topological sense. For example interior entire entire is true.

  • since 1.5
Sourceval (<) : t -> t -> bool

x < y says whether x is strictly weakly less than y i.e., ∀ξ ∈ x, ∃η ∈ y, ξ < η and ∀η ∈ y, ∃ξ ∈ x, ξ < η.

  • since 1.5
Sourceval (>) : t -> t -> bool

x > y iff y < x.

  • since 1.5
Sourceval strict_precedes : t -> t -> bool

strict_precedes x y returns true iff x is to the left and does not touch y.

  • since 1.5
Sourceval disjoint : t -> t -> bool

disjoint x y returns true iff x ∩ y = ∅.

  • since 1.5

Operations

Sourceval width : t -> t

size a returns an interval containing the true width of the interval high a - low a.

Sourceval width_high : t -> number

size_high a returns the width of the interval high a - low a rounded up.

Sourceval width_low : t -> number

size_low a returns the width of the interval high a - low a rounded down.

Sourceval mag : t -> number

mag x returns the magnitude of x, that is sup{ |x| : x ∈ x }.

Sourceval mig : t -> number

mig x returns the mignitude of x, that is inf{ |x| : x ∈ x }.

Sourceval sgn : t -> t

sgn a returns the sign of each bound, e.g., for floats [float (compare (low a) 0.), float (compare (high a) 0.)].

Sourceval truncate : t -> t

truncate a returns the integer interval containing a, that is [floor(low a), ceil(high a)].

Sourceval abs : t -> t

abs a returns the absolute value of the interval, that is

  • a if low a ≥ 0.,
  • ~- a if high a ≤ 0., and
  • [0, max (- low a) (high a)] otherwise.
Sourceval hull : t -> t -> t

hull a b returns the smallest interval containing a and b, that is [min (low a) (low b), max (high a) (high b)].

Sourceval inter_exn : t -> t -> t

inter_exn x y returns the intersection of x and y.

  • since 1.5
Sourceval inter : t -> t -> t option

inter_exn x y returns Some z where z is the intersection of x and y if it is not empty and None if the intersection is empty.

  • since 1.5
Sourceval max : t -> t -> t

max a b returns the "maximum" of the intervals a and b, that is [max (low a) (low b), max (high a) (high b)].

Sourceval min : t -> t -> t

min a b returns the "minimum" of the intervals a and b, that is [min (low a) (low b), min (high a) (high b)].

Sourceval (+) : t -> t -> t

a + b returns [low a +. low b, high a +. high b] properly rounded.

Sourceval (+.) : t -> number -> t

a +. x returns [low a +. x, high a +. x] properly rounded.

Sourceval (+:) : number -> t -> t

x +: a returns [a +. low a, x +. high a] properly rounded.

Sourceval (-) : t -> t -> t

a - b returns [low a -. high b, high a -. low b] properly rounded.

Sourceval (-.) : t -> number -> t

a -. x returns [low a -. x, high a -. x] properly rounded.

Sourceval (-:) : number -> t -> t

x -: a returns [x -. high a, x -. low a] properly rounded.

Sourceval (~-) : t -> t

~- a is the unary negation, it returns [-high a, -low a].

Sourceval (*) : t -> t -> t

a * b multiplies a by b according to interval arithmetic and returns the proper result. If a=zero or b=zero then zero is returned.

Sourceval (*.) : number -> t -> t

x *. a multiplies a by x according to interval arithmetic and returns the proper result. If x=0. then zero is returned.

Sourceval (*:) : t -> number -> t

a *. x multiplies a by x according to interval arithmetic and returns the proper result. If x=0. then zero is returned.

Sourceval (/) : t -> t -> t

a / b divides the first interval by the second according to interval arithmetic and returns the proper result. Raise Interval.Division_by_zero if b=zero.

Sourceval (/.) : t -> number -> t

a /. x divides a by x according to interval arithmetic and returns the proper result. Raise Interval.Division_by_zero if x=0.0.

Sourceval (/:) : number -> t -> t

x /: a divides x by a according to interval arithmetic and returns the result. Raise Interval.Division_by_zero if a=zero.

Sourceval inv : t -> t

inv a returns 1. /: a but is more efficient. Raise Interval.Division_by_zero if a=zero.

Sourcetype 'a one_or_two =
  1. | One of 'a
  2. | Two of 'a * 'a
Sourceval invx : t -> t one_or_two

invx a is the extended division. When 0 ∉ a, the result is One(inv a). If 0 ∈ a, then the two natural intervals (properly rounded) Two([-∞, 1/(low a)], [1/(high a), +∞]) are returned. Raise Interval.Division_by_zero if a=zero.

Sourceval cancelminus : t -> t -> t

cancelminus x y returns the tightest interval z such that x ⊆ z + y. If no such z exists, it returns entire.

  • since 1.5
Sourceval cancelplus : t -> t -> t

cancelplus x y returns the tightest interval z such that x ⊆ z - y. If no such z exists, it returns entire.

  • since 1.5
Sourceval (**) : t -> int -> t

a**n returns interval a raised to nth power according to interval arithmetic. If n=0 then one is returned.