Module Js_float

Provides functions for inspecting and manipulating floats

val _NaN : float

The special value "Not a Number"

val isNaN : float -> 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

val isFinite : float -> 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
val toExponential : float -> string

Formats a float using exponential (scientific) notation

Returns a string representing the given value in exponential notation

  • raises RangeError

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

    (* prints "7.71234e+1" *)
let _ = Js.log (Js.Float.toExponential 77.1234)

(* prints "7.7e+1" *)
let _ = Js.log (Js.Float.toExponential 77.)
val toExponentialWithPrecision : float -> digits:int -> 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)

    ```
(* prints "7.71e+1" *)
let _ = Js.log (Js.Float.toExponentialWithPrecision 77.1234 ~digits:2)
val toFixed : float -> string

Formats a float using fixed point notation

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

  • raises RangeError

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

    (* prints "12346" (note the rounding) *)
let _ = Js.log (Js.Float.toFixed 12345.6789)

(* print "1.2e+21" *)
let _ = Js.log (Js.Float.toFixed 1.2e21)
val toFixedWithPrecision : float -> digits:int -> 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)

    (* prints "12345.7" (note the rounding) *)
let _ = Js.log (Js.Float.toFixedWithPrecision 12345.6789 ~digits:1)

(* prints "0.00" (note the added zeroes) *)
let _ = Js.log (Js.Float.toFixedWithPrecision 0. ~digits:2)
val toPrecision : float -> string

Formats a float using some fairly arbitrary rules

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

toPrecision differs from toFixed in that the former will format the number with full precision, while the latter will not output any digits after the decimal point.

  • raises RangeError

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

    (* prints "12345.6789" *)
let _ = Js.log (Js.Float.toPrecision 12345.6789)

(* print "1.2e+21" *)
let _ = Js.log (Js.Float.toPrecision 1.2e21)
val toPrecisionWithPrecision : float -> digits:int -> 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.

toPrecisionWithPrecision differs from toFixedWithPrecision in that the former will count all digits against the precision, while the latter will count only the digits after the decimal point. toPrecisionWithPrecision 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"?)

    (* prints "1e+4" *)
let _ = Js.log (Js.Float.toPrecisionWithPrecision 12345.6789 ~digits:1)

(* prints "0.0" *)
let _ = Js.log (Js.Float.toPrecisionWithPrecision 0. ~digits:2)
val toString : float -> string

Formats a float as a string

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

(* prints "12345.6789" *)
let _ = Js.log (Js.Float.toString 12345.6789)
val toStringWithRadix : float -> radix:int -> 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)

    (* prints "110" *)
let _ = Js.log (Js.Float.toStringWithRadix 6. ~radix:2)

(* prints "11.001000111101011100001010001111010111000010100011111" *)
let _ = Js.log (Js.Float.toStringWithRadix 3.14 ~radix:2)

(* prints "deadbeef" *)
let _ = Js.log (Js.Float.toStringWithRadix 3735928559. ~radix:16)

(* prints "3f.gez4w97ry0a18ymf6qadcxr" *)
let _ = Js.log (Js.Float.toStringWithRadix 123.456 ~radix:36)
val fromString : string -> float

Parses the given string into a float using JavaScript semantics

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

(* returns 123 *)
let _ = Js.Float.fromString "123"

(* returns 12.3 *)
let _ = Js.Float.fromString "12.3"

(* returns 0 *)
let _ = Js.Float.fromString ""

(* returns 17 *)
let _ = Js.Float.fromString "0x11"

(* returns 3 *)
let _ = Js.Float.fromString "0b11"

(* returns 9 *)
let _ = Js.Float.fromString "0o11"

(* returns [_NaN] *)
let _ = Js.Float.fromString "foo"

(* returns [_NaN] *)
let _ = Js.Float.fromString "100a"