Module Js.Float

Bindings to functions in JavaScript's Number that deal with floats

Provides functions for inspecting and manipulating floats

type t = float;

let _NaN: t;

The special value "Not a Number"

see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/NaN MDN

let isNaN: t => bool;

Tests if the given value is _NaN

Note that both _NaN = _NaN and _NaN == _NaN will return false. isNaN is therefore necessary to test for _NaN.

Returns true if the given value is _NaN, false otherwise

see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isNaN MDN

let isFinite: t => bool;

Tests if the given value is finite

Returns true if the given value is a finite number, false otherwise

(* returns [false] *)
let _ = Js.Float.isFinite infinity

(* returns [false] *)
let _ = Js.Float.isFinite neg_infinity

(* returns [false] *)
let _ = Js.Float.isFinite _NaN

(* returns [true] *)
let _ = Js.Float.isFinite 1234

see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isFinite MDN

let toExponential: ?digits:int => t => string;

Formats a float using exponential (scientific) notation

digits specifies how many digits should appear after the decimal point. The value must be in the range [0, 20] (inclusive).

Returns a string representing the given value in exponential notation

The output will be rounded or padded with zeroes if necessary.

raises RangeError if digits is not in the range [0, 20] (inclusive)

  Js.Float.toExponential 77.1234 = "7.71234e+1"
  Js.Float.toExponential 77. = "7.7e+1"
  Js.Float.toExponential ~digits:2 77.1234 = "7.71e+1"

see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toExponential MDN

let toFixed: ?digits:int => t => string;

Formats a float using fixed point notation

digits specifies how many digits should appear after the decimal point. The value must be in the range [0, 20] (inclusive). Defaults to 0.

Returns a string representing the given value in fixed-point notation (usually)

The output will be rounded or padded with zeroes if necessary.

raises RangeError if digits is not in the range [0, 20] (inclusive)

  Js.Float.toFixed 12345.6789 = "12346"
  Js.Float.toFixed 1.2e21 = "1.2e+21"
  Js.Float.toFixed ~digits:1 12345.6789 = "12345.7"
  Js.Float.toFixed ~digits:2 0. = "0.00"

see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toFixed MDN

let toPrecision: ?digits:int => t => string;

Formats a float using some fairly arbitrary rules

digits specifies how many digits should appear in total. The value must between 0 and some arbitrary number that's hopefully at least larger than 20 (for Node it's 21. Why? Who knows).

Returns a string representing the given value in fixed-point or scientific notation

The output will be rounded or padded with zeroes if necessary.

toPrecision differs from toFixed in that the former will count all digits against the precision, while the latter will count only the digits after the decimal point. toPrecision will also use scientific notation if the specified precision is less than the number for digits before the decimal point.

raises RangeError if digits is not in the range accepted by this function (what do you mean "vague"?)

  Js.Float.toPrecision 12345.6789 = "12345.6789"
  Js.Float.toPrecision 1.2e21 = "1.2e+21"
  Js.Float.toPrecision ~digits:1 12345.6789 = "1e+4"
  Js.Float.toPrecision ~digits:2 0. = "0.0"

see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toPrecision MDN

let toString: ?radix:int => t => string;

Formats a float as a string

radix specifies the radix base to use for the formatted number. The value must be in the range [2, 36] (inclusive).

Returns a string representing the given value in fixed-point (usually)

raises RangeError if radix is not in the range [2, 36] (inclusive)

  Js.Float.toString 12345.6789 = "12345.6789"
  Js.Float.toString ~radix:2 6. = "110"
  Js.Float.toString ~radix:2 3.14 = "11.001000111101011100001010001111010111000010100011111"
  Js.Float.toString ~radix:16 3735928559. = "deadbeef"
  Js.Float.toString ~radix:36 123.456 = "3f.gez4w97ry0a18ymf6qadcxr"

see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toString MDN

let fromString: string => t;

Parses the given string into a float using JavaScript semantics

Returns the number as a float if successfully parsed, _NaN otherwise.

Js.Float.fromString "123" = 123.
Js.Float.fromString "12.3" = 12.3
Js.Float.fromString "" = 0.
Js.Float.fromString "0x11" = 17.
Js.Float.fromString "0b11" = 3.
Js.Float.fromString "0o11" = 9.
Js.Float.fromString "foo" = _NaN
Js.Float.fromString "100a" = _NaN