128 and 256 bits integer and fixed point arithmetics for AssemblyScript. Also support checking overflow/underflow

Usage no npm install needed!

<script type="module">
  import asBignum from '';


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WebAssembly fixed length big numbers written on AssemblyScript

Status: Work in progress

Provide wide numeric types such as u128, u256, i128, i256 and fixed points and also its arithmetic operations.

Namespace safe contain equivalents with overflow/underflow traps.

All kind of types pretty useful for economical and cryptographic usages and provide deterministic behavior.


yarn add as-bignum


npm i as-bignum

Usage via AssemblyScript

import { u128 } from "as-bignum";

declare function logF64(value: f64): void;
declare function logU128(hi: u64, lo: u64): void;

var a = u128.One;
var b = u128.from(-32); // same as u128.from<i32>(-32)
var c = new u128(0x1, -0xF);
var d = u128.from(0x0123456789ABCDEF); // same as u128.from<i64>(0x0123456789ABCDEF)
var e = u128.from('0x0123456789ABCDEF01234567');
var f = u128.fromString('11100010101100101', 2); // same as u128.from('0b11100010101100101')
var r = d / c + (b << 5) + e;

logU128(r.hi, r.lo);

Usage via JavaScript/Typescript


List of types

  • u128 unsigned type (tested)
  • u256 unsigned type (very basic)
  • i128 signed type
  • i256 signed type

  • safe.u128 unsigned type (tested)

  • safe.u256 unsigned type

  • safe.i128 signed type

  • safe.i256 signed type

  • fp128<Q> generic fixed point signed type٭ (very basic for now)
  • fp256<Q> generic fixed point signed type٭

  • safe.fp128<Q> generic fixed point signed type٭
  • safe.fp256<Q> generic fixed point signed type٭

٭ typename Q is a type representing count of fractional bits