paulrberg / evm-bn

Convert fixed-point numbers to ethers big numbers and vice-versa.

Evm Bn

Evm Bn is a utility for converting between stringified fixed-point numbers and Ethers.js BigNumbers, as well as the reverse process. It is particularly useful for projects based on the Ethereum Virtual Machine (EVM), given that 1 ETH is equivalent to 1e18 wei.

• Accepts scientific notation.
• Limits the precision to 78 digits.
• Enforces 60 integer digits and 18 fractional digits.
• Designed to be used alongside @ethersproject/bignumber.
• Slices the fractional digits automatically at position n + 1 and above, with n the number of decimals, rounding down in the process.

Install

$ pnpm add evm-bn

Usage

To Bn

import type { BigNumber } from "@ethersproject/bignumber";
import { toBn } from "evm-bn";

// 3141500000000000000
const foo: BigNumber = toBn("3.1415");

// 115792089237316195423570985008687907853269984665640564039457584007913129639935
const bar: BigNumber = toBn("115792089237316195423570985008687907853269984665640564039457.584007913129639935");

// 100000000000000
const baz: BigNumber = toBn("100e6", 6);

From Bn

import type { BigNumber } from "@ethersproject/bignumber";
import { fromBn } from "evm-bn";

// 3.1415
const foo: BigNumber = fromBn(BigNumber.from("3141500000000000000"));

// 115792089237316195423570985008687907853269984665640564039457.584007913129639935
const bar: BigNumber = fromBn(
  BigNumber.from("115792089237316195423570985008687907853269984665640564039457584007913129639935"),
);

// 100000000
const baz: BigNumber = fromBn(BigNumber.from("100000000000000"), 6);

Contributing

Feel free to dive in! Open an issue, start a discussion or submit a PR.

Set Up

Clone the repositories and install the dependencies:

$ pnpm install

Now you can start making changes.

License

This project is licensed under MIT.

evm-bn's Issues

Some issues with negative exponential numbers (scientific e notation)

I noticed that when representing very small numbers like 10 * 10^-18 (10 with 0 decimals), the following line works: fp("1e-17"), while the following line doesn't fp("10e-18"). Apparently, fp("10e-18") is internally interpreted to be equal to 1 * 10^-18, so does fp("100e-19") and fp("1000e-20").

Feature request: decimals as optional second argument

Make it possible to provide the number of decimals as an optional second argument. The minimum value permitted should be 1, and the maximum 77.

Feature request: ability to change decimals from it's default value (18)

It would make it easier to represent values in certain contexts. E.g., fp("1", 8) for the following example.
In this feature, 18 would be the default number of decimals (e.g., fp("1") is the same as fp("1", 18)).

Run coverage and track it via Coveralls

Add a function that can unwind the conversion

Turn the current default export into a toBn function, and add a new function fromBn that converts from a BigNumber to a string.

Feature request: support ability to write more readable decimal number literals

E.g., fp("10,000,000.256") is a lot easier to read than fp("10000000.256").

Let "decimals" be zero

migrate BigNumber to BigInt

Hi @PaulRBerg, would like to open a PR for this, if you think it's a good idea to migrate as ethers now use bigint in v6.

BigNumber percentage with calculation with evm-bn

Hello, I'm trying to write some TypeScript versions of functions using PRBMath Solidity Library. One thing I am having trouble with is modeling TypeScript functions the same way as the Solidity ones.

For example, in Solidity you can do something like .25e18 to model 25% out as a Big Number, and multiple X by .25e18 to get 25% of X.

uint256 twentyFivePercent = X.mul(.25e18);

With TypeScript, I have not been able to find an equivalent, even with these wonderful libraries like evm-bn. I believe I'm just doing something wrong here, and would love an example for how I can achieve the above using evm-bn.

Thanks!