Float

Double precision (64-bit) floating-point numbers in IEEE 754 representation.

This module contains common floating-point constants and utility functions.

Notation for special values in the documentation below: +inf: Positive infinity -inf: Negative infinity NaN: "not a number" (can have different sign bit values, but NaN != NaN regardless of the sign).

Note: Floating point numbers have limited precision and operations may inherently result in numerical errors.

Examples of numerical errors:

0.1 + 0.1 + 0.1 == 0.3 // => false

1e16 + 1.0 != 1e16 // => false

(and many more cases)

Advice:

Floating point number comparisons by == or != are discouraged. Instead, it is better to compare floating-point numbers with a numerical tolerance, called epsilon.

Example:

import Float "mo:base/Float";
let x = 0.1 + 0.1 + 0.1;
let y = 0.3;

let epsilon = 1e-6; // This depends on the application case (needs a numerical error analysis).
Float.equalWithin(x, y, epsilon) // => true

For absolute precision, it is recommened to encode the fraction number as a pair of a Nat for the base and a Nat for the exponent (decimal point).

NaN sign:

The NaN sign is only applied by abs, neg, and copySign. Other operations can have an arbitrary sign bit for NaN results.

Type `Float`

type Float = Prim.Types.Float

64-bit floating point number type.

Value `pi`

let pi : Float

Ratio of the circumference of a circle to its diameter. Note: Limited precision.

Value `e`

let e : Float

Base of the natural logarithm. Note: Limited precision.

Function `isNaN`

func isNaN(number : Float) : Bool

Determines whether the number is a NaN ("not a number" in the floating point representation). Notes:

Equality test of NaN with itself or another number is always false.
There exist many internal NaN value representations, such as positive and negative NaN, signalling and quiet NaNs, each with many different bit representations.

Example:

import Float "mo:base/Float";

Float.isNaN(0.0/0.0) // => true

Value `abs`

let abs : (x : Float) -> Float

Returns the absolute value of x.

Special cases:

abs(+inf) => +inf
abs(-inf) => +inf
abs(-NaN)  => +NaN
abs(-0.0) => 0.0

Example:

import Float "mo:base/Float";

Float.abs(-1.2) // => 1.2

Value `sqrt`

let sqrt : (x : Float) -> Float

Returns the square root of x.

Special cases:

sqrt(+inf) => +inf
sqrt(-0.0) => -0.0
sqrt(x)    => NaN if x < 0.0
sqrt(NaN)  => NaN

Example:

import Float "mo:base/Float";

Float.sqrt(6.25) // => 2.5

Value `ceil`

let ceil : (x : Float) -> Float

Returns the smallest integral float greater than or equal to x.

Special cases:

ceil(+inf) => +inf
ceil(-inf) => -inf
ceil(NaN)  => NaN
ceil(0.0)  => 0.0
ceil(-0.0) => -0.0

Example:

import Float "mo:base/Float";

Float.ceil(1.2) // => 2.0

Value `floor`

let floor : (x : Float) -> Float

Returns the largest integral float less than or equal to x.

Special cases:

floor(+inf) => +inf
floor(-inf) => -inf
floor(NaN)  => NaN
floor(0.0)  => 0.0
floor(-0.0) => -0.0

Example:

import Float "mo:base/Float";

Float.floor(1.2) // => 1.0

Value `trunc`

let trunc : (x : Float) -> Float

Returns the nearest integral float not greater in magnitude than x. This is equilvent to returning x with truncating its decimal places.

Special cases:

trunc(+inf) => +inf
trunc(-inf) => -inf
trunc(NaN)  => NaN
trunc(0.0)  => 0.0
trunc(-0.0) => -0.0

Example:

import Float "mo:base/Float";

Float.trunc(2.75) // => 2.0

Value `nearest`

let nearest : (x : Float) -> Float

Returns the nearest integral float to x. A decimal place of exactly .5 is rounded up for x > 0 and rounded down for x < 0

Special cases:

nearest(+inf) => +inf
nearest(-inf) => -inf
nearest(NaN)  => NaN
nearest(0.0)  => 0.0
nearest(-0.0) => -0.0

Example:

import Float "mo:base/Float";

Float.nearest(2.75) // => 3.0

Value `copySign`

let copySign : (x : Float, y : Float) -> Float

Returns x if x and y have same sign, otherwise x with negated sign.

The sign bit of zero, infinity, and NaN is considered.

Example:

import Float "mo:base/Float";

Float.copySign(1.2, -2.3) // => -1.2

Value `min`

let min : (x : Float, y : Float) -> Float

Returns the smaller value of x and y.

Special cases:

min(NaN, y) => NaN for any Float y
min(x, NaN) => NaN for any Float x

Example:

import Float "mo:base/Float";

Float.min(1.2, -2.3) // => -2.3 (with numerical imprecision)

Value `max`

let max : (x : Float, y : Float) -> Float

Returns the larger value of x and y.

Special cases:

max(NaN, y) => NaN for any Float y
max(x, NaN) => NaN for any Float x

Example:

import Float "mo:base/Float";

Float.max(1.2, -2.3) // => 1.2

Value `sin`

let sin : (x : Float) -> Float

Returns the sine of the radian angle x.

Special cases:

sin(+inf) => NaN
sin(-inf) => NaN
sin(NaN) => NaN

Example:

import Float "mo:base/Float";

Float.sin(Float.pi / 2) // => 1.0

Value `cos`

let cos : (x : Float) -> Float

Returns the cosine of the radian angle x.

Special cases:

cos(+inf) => NaN
cos(-inf) => NaN
cos(NaN)  => NaN

Example:

import Float "mo:base/Float";

Float.cos(Float.pi / 2) // => 0.0 (with numerical imprecision)

Value `tan`

let tan : (x : Float) -> Float

Returns the tangent of the radian angle x.

Special cases:

tan(+inf) => NaN
tan(-inf) => NaN
tan(NaN)  => NaN

Example:

import Float "mo:base/Float";

Float.tan(Float.pi / 4) // => 1.0 (with numerical imprecision)

Value `arcsin`

let arcsin : (x : Float) -> Float

Returns the arc sine of x in radians.

Special cases:

arcsin(x)   => NaN if x > 1.0
arcsin(x)   => NaN if x < -1.0
arcsin(NaN) => NaN

Example:

import Float "mo:base/Float";

Float.arcsin(1.0) // => Float.pi / 2

Value `arccos`

let arccos : (x : Float) -> Float

Returns the arc cosine of x in radians.

Special cases:

arccos(x)  => NaN if x > 1.0
arccos(x)  => NaN if x < -1.0
arcos(NaN) => NaN

Example:

import Float "mo:base/Float";

Float.arccos(1.0) // => 0.0

Value `arctan`

let arctan : (x : Float) -> Float

Returns the arc tangent of x in radians.

Special cases:

arctan(+inf) => pi / 2
arctan(-inf) => -pi / 2
arctan(NaN)  => NaN

Example:

import Float "mo:base/Float";

Float.arctan(1.0) // => Float.pi / 4

Value `arctan2`

let arctan2 : (y : Float, x : Float) -> Float

Given (y,x), returns the arc tangent in radians of y/x based on the signs of both values to determine the correct quadrant.

Special cases:

arctan2(0.0, 0.0)   => 0.0
arctan2(-0.0, 0.0)  => -0.0
arctan2(0.0, -0.0)  => pi
arctan2(-0.0, -0.0) => -pi
arctan2(+inf, +inf) => pi / 4
arctan2(+inf, -inf) => 3 * pi / 4
arctan2(-inf, +inf) => -pi / 4
arctan2(-inf, -inf) => -3 * pi / 4
arctan2(NaN, x)     => NaN for any Float x
arctan2(y, NaN)     => NaN for any Float y

Example:

import Float "mo:base/Float";

let sqrt2over2 = Float.sqrt(2) / 2;
Float.arctan2(sqrt2over2, sqrt2over2) // => Float.pi / 4

Value `exp`

let exp : (x : Float) -> Float

Returns the value of e raised to the x-th power.

Special cases:

exp(+inf) => +inf
exp(-inf) => 0.0
exp(NaN)  => NaN

Example:

import Float "mo:base/Float";

Float.exp(1.0) // => Float.e

Value `log`

let log : (x : Float) -> Float

Returns the natural logarithm (base-e) of x.

Special cases:

log(0.0)  => -inf
log(-0.0) => -inf
log(x)    => NaN if x < 0.0
log(+inf) => +inf
log(NaN)  => NaN

Example:

import Float "mo:base/Float";

Float.log(Float.e) // => 1.0

Function `format`

func format(fmt : {#fix : Nat8; #exp : Nat8; #gen : Nat8; #hex : Nat8; #exact}, x : Float) : Text

Formatting. format(fmt, x) formats x to Text according to the formatting directive fmt, which can take one of the following forms:

#fix prec as fixed-point format with prec digits
#exp prec as exponential format with prec digits
#gen prec as generic format with prec digits
#hex prec as hexadecimal format with prec digits
#exact as exact format that can be decoded without loss.

-0.0 is formatted with negative sign bit. Positive infinity is formatted as inf. Negative infinity is formatted as -inf. NaN is formatted as NaN or -NaN depending on its sign bit.

Example:

import Float "mo:base/Float";

Float.format(#exp 3, 123.0) // => "1.230e+02"

Value `toText`

let toText : Float -> Text

Conversion to Text. Use format(fmt, x) for more detailed control.

-0.0 is formatted with negative sign bit. Positive infinity is formatted as inf. Negative infinity is formatted as -inf. NaN is formatted as NaN or -NaN depending on its sign bit.

Example:

import Float "mo:base/Float";

Float.toText(0.12) // => "0.12"

Value `toInt64`

let toInt64 : Float -> Int64

Conversion to Int64 by truncating Float, equivalent to toInt64(trunc(f))

Traps if the floating point number is larger or smaller than the representable Int64. Also traps for inf, -inf, and NaN.

Example:

import Float "mo:base/Float";

Float.toInt64(-12.3) // => -12

Value `fromInt64`

let fromInt64 : Int64 -> Float

Conversion from Int64.

Note: The floating point number may be imprecise for large or small Int64.

Example:

import Float "mo:base/Float";

Float.fromInt64(-42) // => -42.0

Value `toInt`

let toInt : Float -> Int

Conversion to Int.

Traps for inf, -inf, and NaN.

Example:

import Float "mo:base/Float";

Float.toInt(1.2e6) // => +1_200_000

Value `fromInt`

let fromInt : Int -> Float

Conversion from Int. May result in Inf.

Note: The floating point number may be imprecise for large or small Int values. Returns inf if the integer is greater than the maximum floating point number. Returns -inf if the integer is less than the minimum floating point number.

Example:

import Float "mo:base/Float";

Float.fromInt(-123) // => -123.0

Function `equal`

func equal(x : Float, y : Float) : Bool

Returns x == y. @deprecated Use Float.equalWithin() as this function does not consider numerical errors.

Function `notEqual`

func notEqual(x : Float, y : Float) : Bool

Returns x != y. @deprecated Use Float.notEqualWithin() as this function does not consider numerical errors.

Function `equalWithin`

func equalWithin(x : Float, y : Float, epsilon : Float) : Bool

Determines whether x is equal to y within the defined tolerance of epsilon. The epsilon considers numerical erros, see comment above. Equivalent to Float.abs(x - y) <= epsilon for a non-negative epsilon.

Traps if epsilon is negative or NaN.

Special cases:

equalWithin(+0.0, -0.0, epsilon) => true for any `epsilon >= 0.0`
equalWithin(-0.0, +0.0, epsilon) => true for any `epsilon >= 0.0`
equalWithin(+inf, +inf, epsilon) => true for any `epsilon >= 0.0`
equalWithin(-inf, -inf, epsilon) => true for any `epsilon >= 0.0`
equalWithin(x, NaN, epsilon)     => false for any x and `epsilon >= 0.0`
equalWithin(NaN, y, epsilon)     => false for any y and `epsilon >= 0.0`

Example:

import Float "mo:base/Float";

let epsilon = 1e-6;
Float.equalWithin(-12.3, -1.23e1, epsilon) // => true

Function `notEqualWithin`

func notEqualWithin(x : Float, y : Float, epsilon : Float) : Bool

Determines whether x is not equal to y within the defined tolerance of epsilon. The epsilon considers numerical erros, see comment above. Equivalent to not equal(x, y, epsilon).

Traps if epsilon is negative or NaN.

Special cases:

notEqualWithin(+0.0, -0.0, epsilon) => false for any `epsilon >= 0.0`
notEqualWithin(-0.0, +0.0, epsilon) => false for any `epsilon >= 0.0`
notEqualWithin(+inf, +inf, epsilon) => false for any `epsilon >= 0.0`
notEqualWithin(-inf, -inf, epsilon) => false for any `epsilon >= 0.0`
notEqualWithin(x, NaN, epsilon)     => true for any x and `epsilon >= 0.0`
notEqualWithin(NaN, y, epsilon)     => true for any y and `epsilon >= 0.0`

Example:

import Float "mo:base/Float";

let epsilon = 1e-6;
Float.notEqualWithin(-12.3, -1.23e1, epsilon) // => false

Function `less`

func less(x : Float, y : Float) : Bool

Returns x < y.

Special cases:

less(+0.0, -0.0) => false
less(-0.0, +0.0) => false
less(NaN, y)     => false for any Float y
less(x, NaN)     => false for any Float x

Example:

import Float "mo:base/Float";

Float.less(Float.e, Float.pi) // => true

Function `lessOrEqual`

func lessOrEqual(x : Float, y : Float) : Bool

Returns x <= y.

Special cases:

lessOrEqual(+0.0, -0.0) => true
lessOrEqual(-0.0, +0.0) => true
lessOrEqual(NaN, y)     => false for any Float y
lessOrEqual(x, NaN)     => false for any Float x

Example:

import Float "mo:base/Float";

Float.lessOrEqual(0.123, 0.1234) // => true

Function `greater`

func greater(x : Float, y : Float) : Bool

Returns x > y.

Special cases:

greater(+0.0, -0.0) => false
greater(-0.0, +0.0) => false
greater(NaN, y)     => false for any Float y
greater(x, NaN)     => false for any Float x

Example:

import Float "mo:base/Float";

Float.greater(Float.pi, Float.e) // => true

Function `greaterOrEqual`

func greaterOrEqual(x : Float, y : Float) : Bool

Returns x >= y.

Special cases:

greaterOrEqual(+0.0, -0.0) => true
greaterOrEqual(-0.0, +0.0) => true
greaterOrEqual(NaN, y)     => false for any Float y
greaterOrEqual(x, NaN)     => false for any Float x

Example:

import Float "mo:base/Float";

Float.greaterOrEqual(0.1234, 0.123) // => true

Function `compare`

func compare(x : Float, y : Float) : {#less; #equal; #greater}

Defines a total order of x and y for use in sorting.

Note: Using this operation to determine equality or inequality is discouraged for two reasons:

It does not consider numerical errors, see comment above. Use equalWithin(x, y, espilon) or notEqualWithin(x, y, epsilon) to test for equality or inequality, respectively.
NaN are here considered equal if their sign matches, which is different to the standard equality by == or when using equal() or notEqual().

Total order:

negative NaN (no distinction between signalling and quiet negative NaN)
negative infinity
negative numbers (including negative subnormal numbers in standard order)
negative zero (-0.0)
positive zero (+0.0)
positive numbers (including positive subnormal numbers in standard order)
positive infinity
positive NaN (no distinction between signalling and quiet positive NaN)

Example:

import Float "mo:base/Float";

Float.compare(0.123, 0.1234) // => #less

Function `neg`

func neg(x : Float) : Float

Returns the negation of x, -x .

Changes the sign bit for infinity.

Special cases:

neg(+inf) => -inf
neg(-inf) => +inf
neg(+NaN) => -NaN
neg(-NaN) => +NaN
neg(+0.0) => -0.0
neg(-0.0) => +0.0

Example:

import Float "mo:base/Float";

Float.neg(1.23) // => -1.23

Function `add`

func add(x : Float, y : Float) : Float

Returns the sum of x and y, x + y.

Note: Numerical errors may occur, see comment above.

Special cases:

add(+inf, y)    => +inf if y is any Float except -inf and NaN
add(-inf, y)    => -inf if y is any Float except +inf and NaN
add(+inf, -inf) => NaN
add(NaN, y)     => NaN for any Float y

The same cases apply commutatively, i.e. for add(y, x).

Example:

import Float "mo:base/Float";

Float.add(1.23, 0.123) // => 1.353

Function `sub`

func sub(x : Float, y : Float) : Float

Returns the difference of x and y, x - y.

Note: Numerical errors may occur, see comment above.

Special cases:

sub(+inf, y)    => +inf if y is any Float except +inf or NaN
sub(-inf, y)    => -inf if y is any Float except -inf and NaN
sub(x, +inf)    => -inf if x is any Float except +inf and NaN
sub(x, -inf)    => +inf if x is any Float except -inf and NaN
sub(+inf, +inf) => NaN
sub(-inf, -inf) => NaN
sub(NaN, y)     => NaN for any Float y
sub(x, NaN)     => NaN for any Float x

Example:

import Float "mo:base/Float";

Float.sub(1.23, 0.123) // => 1.107

Function `mul`

func mul(x : Float, y : Float) : Float

Returns the product of x and y, x * y.

Note: Numerical errors may occur, see comment above.

Special cases:

mul(+inf, y) => +inf if y > 0.0
mul(-inf, y) => -inf if y > 0.0
mul(+inf, y) => -inf if y < 0.0
mul(-inf, y) => +inf if y < 0.0
mul(+inf, 0.0) => NaN
mul(-inf, 0.0) => NaN
mul(NaN, y) => NaN for any Float y

The same cases apply commutatively, i.e. for mul(y, x).

Example:

import Float "mo:base/Float";

Float.mul(1.23, 1e2) // => 123.0

Function `div`

func div(x : Float, y : Float) : Float

Returns the division of x by y, x / y.

Note: Numerical errors may occur, see comment above.

Special cases:

div(0.0, 0.0) => NaN
div(x, 0.0)   => +inf for x > 0.0
div(x, 0.0)   => -inf for x < 0.0
div(x, +inf)  => 0.0 for any x except +inf, -inf, and NaN
div(x, -inf)  => 0.0 for any x except +inf, -inf, and NaN
div(+inf, y)  => +inf if y >= 0.0
div(+inf, y)  => -inf if y < 0.0
div(-inf, y)  => -inf if y >= 0.0
div(-inf, y)  => +inf if y < 0.0
div(NaN, y)   => NaN for any Float y
div(x, NaN)   => NaN for any Float x

Example:

import Float "mo:base/Float";

Float.div(1.23, 1e2) // => 0.0123

Function `rem`

func rem(x : Float, y : Float) : Float

Returns the floating point division remainder x % y, which is defined as x - trunc(x / y) * y.

Note: Numerical errors may occur, see comment above.

Special cases:

rem(0.0, 0.0) => NaN
rem(x, y)     => +inf if sign(x) == sign(y) for any x and y not being +inf, -inf, or NaN
rem(x, y)     => -inf if sign(x) != sign(y) for any x and y not being +inf, -inf, or NaN
rem(x, +inf)  => x for any x except +inf, -inf, and NaN
rem(x, -inf)  => x for any x except +inf, -inf, and NaN
rem(+inf, y)  => NaN for any Float y
rem(-inf, y)  => NaN for any Float y
rem(NaN, y)   => NaN for any Float y
rem(x, NaN)   => NaN for any Float x

Example:

import Float "mo:base/Float";

Float.rem(7.2, 2.3) // => 0.3 (with numerical imprecision)

Function `pow`

func pow(x : Float, y : Float) : Float

Returns x to the power of y, x ** y.

Note: Numerical errors may occur, see comment above.

Special cases:

pow(+inf, y)    => +inf for any y > 0.0 including +inf
pow(+inf, 0.0)  => 1.0
pow(+inf, y)    => 0.0 for any y < 0.0 including -inf
pow(x, +inf)    => +inf if x > 0.0 or x < 0.0
pow(0.0, +inf)  => 0.0
pow(x, -inf)    => 0.0 if x > 0.0 or x < 0.0
pow(0.0, -inf)  => +inf
pow(x, y)       => NaN if x < 0.0 and y is a non-integral Float
pow(-inf, y)    => +inf if y > 0.0 and y is a non-integral or an even integral Float
pow(-inf, y)    => -inf if y > 0.0 and y is an odd integral Float
pow(-inf, 0.0)  => 1.0
pow(-inf, y)    => 0.0 if y < 0.0
pow(-inf, +inf) => +inf
pow(-inf, -inf) => 1.0
pow(NaN, y)     => NaN if y != 0.0
pow(NaN, 0.0)   => 1.0
pow(x, NaN)     => NaN for any Float x

Example:

import Float "mo:base/Float";

Float.pow(2.5, 2.0) // => 6.25

Float

Type Float​

Value pi​

Value e​

Function isNaN​

Value abs​

Value sqrt​

Value ceil​

Value floor​

Value trunc​

Value nearest​

Value copySign​

Value min​

Value max​

Value sin​

Value cos​

Value tan​

Value arcsin​

Value arccos​

Value arctan​

Value arctan2​

Value exp​

Value log​

Function format​

Value toText​

Value toInt64​

Value fromInt64​

Value toInt​

Value fromInt​

Function equal​

Function notEqual​

Function equalWithin​

Function notEqualWithin​

Function less​

Function lessOrEqual​

Function greater​

Function greaterOrEqual​

Function compare​

Function neg​

Function add​

Function sub​

Function mul​

Function div​

Function rem​

Function pow​

Type `Float`

Value `pi`

Value `e`

Function `isNaN`

Value `abs`

Value `sqrt`

Value `ceil`

Value `floor`

Value `trunc`

Value `nearest`

Value `copySign`

Value `min`

Value `max`

Value `sin`

Value `cos`

Value `tan`

Value `arcsin`

Value `arccos`

Value `arctan`

Value `arctan2`

Value `exp`

Value `log`

Function `format`

Value `toText`

Value `toInt64`

Value `fromInt64`

Value `toInt`

Value `fromInt`

Function `equal`

Function `notEqual`

Function `equalWithin`

Function `notEqualWithin`

Function `less`

Function `lessOrEqual`

Function `greater`

Function `greaterOrEqual`

Function `compare`

Function `neg`

Function `add`

Function `sub`

Function `mul`

Function `div`

Function `rem`

Function `pow`