Function to compute nth root

contracts/staking/contracts/src/libs/LibMath.sol

@@ -0,0 +1,75 @@
+
+
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.5.5;
+
+
+
+library LibMath {
+    
+    function _nthRoot(uint256 base, uint256 n) internal pure returns (uint256 root) {
+        assembly {
+            ///// Implements Newton's Approximation, derived from Newton's nth Root Algorithm /////
+            // See https://en.wikipedia.org/wiki/Nth_root#nth_root_algorithm
+            // 1. Find greatest power-of-2 <= `value`
+            let m := 0
+            for {let v := base}
+                gt(v, 0)
+                {v := shr(1, v)}
+            {
+                m := add(m, 1)
+            }
+            m := sub(m, 1)
+
+            // 2. Find greatest power-of-2 that, when raised to the power of `n`,
+            //    is <= `value`
+            let x := exp(2, div(m, n))
+
+            // 3. Find y such that `x` + `y` = `value`
+            let y := xor(base, exp(2, mul(div(m, n), n)))
+
+            // 4. Run Newton's Approximation to find the root
+            root := add(x, div(y, mul(n, exp(2, mul(div(m, n), sub(n, 1))))))
+
+            /**
+             * Note 1:
+             * On some clients (like ganache), execution freezes when running exponentiation
+             * with a dynamically generated base. Because of this, all exponentiation above
+             * is done base-2.
+             * Example:
+             * Call the solidity function below with `n >= 1` and execution will timeout.
+             *
+             *      function repro(uint256 n) public pure returns (uint256) {
+             *          uint256 m = 2**n;
+             *          return m**n;
+             *      }
+             *
+             * Call a similar function with the same input _does not_ timeout:
+             *
+             *  function fix(uint256 n) public pure returns (uint256) {
+             *      uint256 m = 2**(n*n);
+             *       return m;
+             *   }
+             */
+        }
+    }
+}
+
+

contracts/staking/contracts/test/LibMathTest.sol

@@ -0,0 +1,33 @@
+
+
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity ^0.5.5;
+
+import "../src/libs/LibMath.sol";
+
+
+contract LibMathTest {
+    
+    function nthRoot(uint256 base, uint256 n) public pure returns (uint256 root) {
+        return LibMath._nthRoot(base, n);
+    }
+}
+
+

contracts/staking/package.json

@@ -35,7 +35,7 @@
         "compile:truffle": "truffle compile"
     },
     "config": {
-        "abis": "./generated-artifacts/@(LibZrxToken|MixinStake|MixinVaultCore|Staking|ZrxVault).json",
+        "abis": "./generated-artifacts/@(LibMathTest|LibZrxToken|MixinStake|MixinVaultCore|Staking|ZrxVault).json",
         "abis:comment": "This list is auto-generated by contracts-gen. Don't edit manually."
     },
     "repository": {

contracts/staking/src/artifacts.ts

@@ -5,6 +5,7 @@
  */
 import { ContractArtifact } from 'ethereum-types';
 
+import * as LibMathTest from '../generated-artifacts/LibMathTest.json';
 import * as LibZrxToken from '../generated-artifacts/LibZrxToken.json';
 import * as MixinStake from '../generated-artifacts/MixinStake.json';
 import * as MixinVaultCore from '../generated-artifacts/MixinVaultCore.json';
@@ -16,4 +17,5 @@ export const artifacts = {
     LibZrxToken: LibZrxToken as ContractArtifact,
     MixinVaultCore: MixinVaultCore as ContractArtifact,
     ZrxVault: ZrxVault as ContractArtifact,
+    LibMathTest: LibMathTest as ContractArtifact,
 };

contracts/staking/src/wrappers.ts

@@ -3,6 +3,7 @@
  * Warning: This file is auto-generated by contracts-gen. Don't edit manually.
  * -----------------------------------------------------------------------------
  */
+export * from '../generated-wrappers/lib_math_test';
 export * from '../generated-wrappers/lib_zrx_token';
 export * from '../generated-wrappers/mixin_stake';
 export * from '../generated-wrappers/mixin_vault_core';

contracts/staking/test/core_test.ts

@@ -108,6 +108,13 @@ describe('Staking Core', () => {
                 expect(zrxTokenBalanceOfStakerAfterStaking).to.be.bignumber.equal(zrxTokenBalanceOfStakerBeforeStaking.minus(amountToStake).plus(amountToUnstake));
             }
         });
+
+        it('nth root', async () => {
+            const base = new BigNumber(1419857);
+            const n = new BigNumber(5);
+            const root = await stakingWrapper.nthRoot(base, n);
+            expect(root).to.be.bignumber.equal(17);
+        });
     });
 });
 // tslint:enable:no-unnecessary-type-assertion

contracts/staking/test/utils/staking_wrapper.ts

@@ -8,7 +8,7 @@ import { DummyERC20TokenContract } from '@0x/contracts-erc20';
 import { ERC20ProxyContract } from '@0x/contracts-asset-proxy';
 import * as _ from 'lodash';
 
-import { artifacts, StakingContract, ZrxVaultContract } from '../../src';
+import { artifacts, StakingContract, ZrxVaultContract, LibMathTestContract } from '../../src';
 
 const expect = chai.expect;
 
@@ -21,6 +21,7 @@ export class StakingWrapper {
     private readonly _zrxTokenContract: DummyERC20TokenContract;
     private _stakingContractIfExists?: StakingContract;
     private _zrxVaultContractIfExists?: ZrxVaultContract;
+    private _libMathTestContractIfExists?: LibMathTestContract;
 
     constructor(provider: Provider, ownerAddres: string, erc20ProxyContract: ERC20ProxyContract, zrxTokenContract: DummyERC20TokenContract) {
         this._web3Wrapper = new Web3Wrapper(provider);
@@ -38,6 +39,10 @@ export class StakingWrapper {
         this._validateDeployedOrThrow();
         return this._zrxVaultContractIfExists as ZrxVaultContract;
     }
+    public getLibMathTestContract(): LibMathTestContract {
+        this._validateDeployedOrThrow();
+        return this._libMathTestContractIfExists as LibMathTestContract;
+    }
     public async deployAndConfigureContracts(): Promise<void> {
         // deploy zrx vault
         const zrxAssetData = assetDataUtils.encodeERC20AssetData(this._zrxTokenContract.address);
@@ -59,7 +64,13 @@ export class StakingWrapper {
             (this._zrxVaultContractIfExists as ZrxVaultContract).address
         );
         // set staking contract in zrx vault
-        await this.getZrxVaultContract().setStakingContractAddrsess.awaitTransactionSuccessAsync((this._stakingContractIfExists as StakingContract).address);
+        await (this._zrxVaultContractIfExists as ZrxVaultContract).setStakingContractAddrsess.awaitTransactionSuccessAsync((this._stakingContractIfExists as StakingContract).address);
+        // deploy libmath test
+        this._libMathTestContractIfExists = await LibMathTestContract.deployFrom0xArtifactAsync(
+            artifacts.LibMathTest,
+            this._provider,
+            txDefaults,
+        );
     }
     public async stake(holder: string, amount: BigNumber): Promise<BigNumber> {
         const stakeMinted = await this.getStakingContract().stake.callAsync(amount, {from: holder});
@@ -87,6 +98,10 @@ export class StakingWrapper {
         const balance = await this._zrxTokenContract.balanceOf.callAsync(this.getZrxVaultContract().address);
         return balance;
     }
+    public async nthRoot(value: BigNumber, n: BigNumber): Promise<BigNumber> {
+        const output = await this.getLibMathTestContract().nthRoot.callAsync(value, n);
+        return output;
+    }
     public toBaseUnitAmount(amount: BigNumber | number): BigNumber {
         const decimals = 18;
         const amountAsBigNumber = typeof(amount)  === 'number' ? new BigNumber(amount) : amount;
@@ -97,6 +112,8 @@ export class StakingWrapper {
             throw new Error('Staking contract not deployed. Call `deployStakingContracts`');
         } else if (this._zrxVaultContractIfExists === undefined) {
             throw new Error('ZRX Vault contract not deployed. Call `deployStakingContracts`');
+        } else if (this._libMathTestContractIfExists === undefined) {
+            throw new Error('LibMathTest contract not deployed. Call `deployStakingContracts`');
         }
     }
 }

contracts/staking/tsconfig.json

@@ -3,6 +3,7 @@
     "compilerOptions": { "outDir": "lib", "rootDir": ".", "resolveJsonModule": true },
     "include": ["./src/**/*", "./test/**/*", "./generated-wrappers/**/*"],
     "files": [
+        "generated-artifacts/LibMathTest.json",
         "generated-artifacts/LibZrxToken.json",
         "generated-artifacts/MixinStake.json",
         "generated-artifacts/MixinVaultCore.json",