aave-protocol-v2/test/helpers/utils/math.ts

import BigNumber from "bignumber.js";
import {
  RAY,
  WAD,
  HALF_RAY,
  HALF_WAD,
  WAD_RAY_RATIO,
} from "../../../helpers/constants";

declare module "bignumber.js" {
  interface BigNumber {
    ray: () => BigNumber;
    wad: () => BigNumber;
    halfRay: () => BigNumber;
    halfWad: () => BigNumber;
    wadMul: (a: BigNumber) => BigNumber;
    wadDiv: (a: BigNumber) => BigNumber;
    rayMul: (a: BigNumber) => BigNumber;
    rayDiv: (a: BigNumber) => BigNumber;
    rayToWad: () => BigNumber;
    wadToRay: () => BigNumber;
    rayPow: (n: BigNumber) => BigNumber;
  }
}

BigNumber.prototype.ray = (): BigNumber => {
  return new BigNumber(RAY).decimalPlaces(0);
};
BigNumber.prototype.wad = (): BigNumber => {
  return new BigNumber(WAD).decimalPlaces(0);
};

BigNumber.prototype.halfRay = (): BigNumber => {
  return new BigNumber(HALF_RAY).decimalPlaces(0, BigNumber.ROUND_DOWN);
};

BigNumber.prototype.halfWad = (): BigNumber => {
  return new BigNumber(HALF_WAD).decimalPlaces(0, BigNumber.ROUND_DOWN);
};

BigNumber.prototype.wadMul = function (b: BigNumber): BigNumber {
  return this.halfWad()
    .plus(this.multipliedBy(b))
    .div(WAD)
    .decimalPlaces(0, BigNumber.ROUND_DOWN);
};

BigNumber.prototype.wadDiv = function (a: BigNumber): BigNumber {
  const halfA = a.div(2).decimalPlaces(0, BigNumber.ROUND_DOWN);

  return halfA
    .plus(this.multipliedBy(WAD))
    .div(a)
    .decimalPlaces(0, BigNumber.ROUND_DOWN);
};

BigNumber.prototype.rayMul = function (a: BigNumber): BigNumber {
  return this.halfRay()
    .plus(this.multipliedBy(a))
    .div(RAY)
    .decimalPlaces(0, BigNumber.ROUND_DOWN);
};

BigNumber.prototype.rayDiv = function (a: BigNumber): BigNumber {
  const halfA = a.div(2).decimalPlaces(0, BigNumber.ROUND_DOWN);

  return halfA
    .plus(this.multipliedBy(RAY))
    .decimalPlaces(0, BigNumber.ROUND_DOWN)
    .div(a)
    .decimalPlaces(0, BigNumber.ROUND_DOWN);
};

BigNumber.prototype.rayToWad = function (): BigNumber {
  const halfRatio = new BigNumber(WAD_RAY_RATIO).div(2);

  return halfRatio
    .plus(this)
    .div(WAD_RAY_RATIO)
    .decimalPlaces(0, BigNumber.ROUND_DOWN);
};

BigNumber.prototype.wadToRay = function (): BigNumber {
  return this.multipliedBy(WAD_RAY_RATIO).decimalPlaces(
    0,
    BigNumber.ROUND_DOWN
  );
};

BigNumber.prototype.rayPow = function (n: BigNumber): BigNumber {
  let z = !n.modulo(2).eq(0) ? this : new BigNumber(RAY);
  let x = new BigNumber(this);

  for (n = n.div(2); !n.eq(0); n = n.div(2)) {
    x = x.rayMul(x);

    if (!n.modulo(2).eq(0)) {
      z = z.rayMul(x);
    }
  }
  return z;
};