# Math

Mathematical operations as known from JavaScript.

The Math API is very much like JavaScript's (MDN (opens new window)), with the notable exceptions stated above and rest parameters not being supported yet.

# Variants

Math in AssemblyScript is available in multiple variants.

Variant Description
NativeMath WebAssembly implementation for f64
NativeMathf WebAssembly implementation for f32
JSMath JavaScript implementation for f64 (imported from the host)

By default, the global Math object is an alias of NativeMath and Mathf is an alias of NativeMathf .

# Using NativeMath

This is the default, so no additional configuration options are required. Note, however, that Math.random needs a way to seed the random number generator in this scenario, which WebAssembly alone cannot do, hence a function env.seed() is imported from the host (see also) that must return an f64 value (the seed). The loader and import "WASI" automatically take care of providing the seed function in this scenario, but one can always implement their own, for example to make the PRNG deterministic by returning a fixed seed value.

# Using JSMath

Where small module size is more important than performance, one can opt to override the default by adding --use Math=JSMath on the command line, essentially aliasing Math with JSMath instead, which maps to an import of the browser's math implementation. Naturally, this option requires importing the browser's Math object as a whole, but does not require seeding / is not seedable. The loader automatically takes care of importing the browser's math in this scenario.

# Static members

The type T below substitutes either f32 or f64 depending on the implementation used. Note that Math is not actually generic, but concrete implementations like Math and Mathf have an identical interface that only differs in the implementation's floating-point precision denoted by T.

# Constants

  • const E: T

    The base of natural logarithms, e, approximately 2.718.

  • const LN2: T

    The natural logarithm of 2, approximately 0.693.

  • const LN10: T

    The natural logarithm of 10, approximately 2.302.

  • const LOG2E: T

    The base 2 logarithm of e, approximately 1.442.

  • const LOG10E: T

    The base 10 logarithm of e, approximately 0.434.

  • const PI: T

    The ratio of the circumference of a circle to its diameter, approximately 3.14159.

  • const SQRT1_2: T

    The square root of 1/2, approximately 0.707.

  • const SQRT2: T

    The square root of 2, approximately 1.414.

# Functions

  • function abs(x: T): T

    Returns the absolute value of x.

  • function acos(x: T): T

    Returns the arccosine (in radians) of x.

  • function acosh(x: T): T

    Returns the hyperbolic arc-cosine of x.

  • function asin(x: T): T

    Returns the arcsine (in radians) of x.

  • function asinh(x: T): T

    Returns the hyperbolic arcsine of x.

  • function atan(x: T): T

    Returns the arctangent (in radians) of x.

  • function atan2(y: T, x: T): T

    Returns the arctangent of the quotient of its arguments.

  • function atanh(x: T): T

    Returns the hyperbolic arctangent of x.

  • function cbrt(x: T): T

    Returns the cube root of x.

  • function ceil(x: T): T

    Returns the smallest integer greater than or equal to x.

  • function clz32(x: T): T

    Returns the number of leading zero bits in the 32-bit binary representation of x.

  • function cos(x: T): T

    Returns the cosine (in radians) of x.

  • function cosh(x: T): T

    Returns the hyperbolic cosine of x.

  • function exp(x: T): T

    Returns e to the power of x.

  • function expm1(x: T): T

    Returns e to the power of x, minus 1.

  • function floor(x: T): T

    Returns the largest integer less than or equal to x.

  • function fround(x: T): T

    Returns the nearest 32-bit single precision float representation of x.

  • function hypot(value1: T, value2: T): T

    Returns the square root of the sum of squares of its arguments.

  • function imul(a: T, b: T): T

    Returns the result of the C-like 32-bit multiplication of a and b.

  • function log(x: T): T

    Returns the natural logarithm (base e) of x.

  • function log10(x: T): T

    Returns the base 10 logarithm of x.

  • function log1p(x: T): T

    Returns the natural logarithm (base e) of 1 + x.

  • function log2(x: T): T

    Returns the base 2 logarithm of x.

  • function max(value1: T, value2: T): T

    Returns the largest-valued number of its arguments.

  • function min(value1: T, value2: T): T

    Returns the lowest-valued number of its arguments.

  • function pow(base: T, exponent: T): T

    Returns base to the power of exponent.

  • function random(): T

    Returns a pseudo-random number in the range from 0.0 inclusive up to but not including 1.0.


    Seeding happens automatically in common scenarios. See the notes on using NativeMath above if it doesn't.

  • function round(x: T): T

    Returns the value of x rounded to the nearest integer.

  • function sign(x: T): T

    Returns the sign of x, indicating whether the number is positive, negative or zero.

  • function signbit(x: T): bool

    Returns whether the sign bit of x is set.

  • function sin(x: T): T

    Returns the sine of x.

  • function sinh(x: T): T

    Returns the hyperbolic sine of x.

  • function sqrt(x: T): T

    Returns the square root of x.

  • function tan(x: T): T

    Returns the tangent of x.

  • function tanh(x: T): T

    Returns the hyperbolic tangent of x.

  • function trunc(x: T): T

    Returns the integer part of x by removing any fractional digits.

# Considerations

The Math implementations are meant as a drop-in replacement for JavaScript's Math so sometimes mimic special JavaScript semantics, like Math.round always rounding towards +Infinity. Also, functions like Math.fround or Math.imul do not return an f32 respectively an i32 as some might expect for the same reason. Hence, depending on the use case, using WebAssembly's math instructions directly can be a worthwhile alternative where portability is not a concern.