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pragma solidity ^0.4.0; |
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// SPDX-License-Identifier: GPL-3.0 |
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/// @title Voting with delegation. |
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pragma solidity >=0.7.0 <0.9.0; |
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/** |
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* @title Ballot |
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* @dev Implements voting process along with vote delegation |
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*/ |
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contract Ballot { |
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// This declares a new complex type which will |
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// be used for variables later. |
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// It will represent a single voter. |
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struct Voter { |
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uint weight; // weight is accumulated by delegation |
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bool voted; // if true, that person already voted |
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@ -12,33 +15,31 @@ contract Ballot { |
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uint vote; // index of the voted proposal |
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} |
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// This is a type for a single proposal. |
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struct Proposal { |
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// If you can limit the length to a certain number of bytes, |
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// always use one of bytes1 to bytes32 because they are much cheaper |
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bytes32 name; // short name (up to 32 bytes) |
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uint voteCount; // number of accumulated votes |
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} |
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address public chairperson; |
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// This declares a state variable that |
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// stores a \`Voter\` struct for each possible address. |
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mapping(address => Voter) public voters; |
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// A dynamically-sized array of \`Proposal\` structs. |
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Proposal[] public proposals; |
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/// Create a new ballot to choose one of \`proposalNames\`. |
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function Ballot(bytes32[] proposalNames) { |
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/** |
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* @dev Create a new ballot to choose one of 'proposalNames'. |
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* @param proposalNames names of proposals |
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*/ |
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constructor(bytes32[] memory proposalNames) { |
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chairperson = msg.sender; |
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voters[chairperson].weight = 1; |
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// For each of the provided proposal names, |
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// create a new proposal object and add it |
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// to the end of the array. |
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for (uint i = 0; i < proposalNames.length; i++) { |
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// \`Proposal({...})\` creates a temporary |
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// Proposal object and \`proposals.push(...)\` |
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// appends it to the end of \`proposals\`. |
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// 'Proposal({...})' creates a temporary |
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// Proposal object and 'proposals.push(...)' |
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// appends it to the end of 'proposals'. |
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proposals.push(Proposal({ |
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name: proposalNames[i], |
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voteCount: 0 |
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@ -46,98 +47,92 @@ contract Ballot { |
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} |
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} |
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// Give \`voter\` the right to vote on this ballot. |
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// May only be called by \`chairperson\`. |
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function giveRightToVote(address voter) { |
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if (msg.sender != chairperson || voters[voter].voted) { |
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// \`throw\` terminates and reverts all changes to |
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// the state and to Ether balances. It is often |
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// a good idea to use this if functions are |
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// called incorrectly. But watch out, this |
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// will also consume all provided gas. |
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throw; |
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} |
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/** |
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* @dev Give 'voter' the right to vote on this ballot. May only be called by 'chairperson'. |
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* @param voter address of voter |
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*/ |
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function giveRightToVote(address voter) public { |
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require( |
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msg.sender == chairperson, |
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"Only chairperson can give right to vote." |
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); |
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require( |
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!voters[voter].voted, |
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"The voter already voted." |
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); |
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require(voters[voter].weight == 0); |
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voters[voter].weight = 1; |
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} |
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/// Delegate your vote to the voter \`to\`. |
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function delegate(address to) { |
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// assigns reference |
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Voter sender = voters[msg.sender]; |
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if (sender.voted) |
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throw; |
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// Forward the delegation as long as |
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// \`to\` also delegated. |
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// In general, such loops are very dangerous, |
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// because if they run too long, they might |
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// need more gas than is available in a block. |
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// In this case, the delegation will not be executed, |
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// but in other situations, such loops might |
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// cause a contract to get "stuck" completely. |
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while ( |
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voters[to].delegate != address(0) && |
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voters[to].delegate != msg.sender |
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) { |
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/** |
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* @dev Delegate your vote to the voter 'to'. |
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* @param to address to which vote is delegated |
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*/ |
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function delegate(address to) public { |
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Voter storage sender = voters[msg.sender]; |
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require(!sender.voted, "You already voted."); |
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require(to != msg.sender, "Self-delegation is disallowed."); |
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while (voters[to].delegate != address(0)) { |
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to = voters[to].delegate; |
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} |
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// We found a loop in the delegation, not allowed. |
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if (to == msg.sender) { |
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throw; |
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// We found a loop in the delegation, not allowed. |
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require(to != msg.sender, "Found loop in delegation."); |
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} |
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// Since \`sender\` is a reference, this |
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// modifies \`voters[msg.sender].voted\` |
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sender.voted = true; |
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sender.delegate = to; |
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Voter delegate = voters[to]; |
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if (delegate.voted) { |
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Voter storage delegate_ = voters[to]; |
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if (delegate_.voted) { |
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// If the delegate already voted, |
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// directly add to the number of votes |
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proposals[delegate.vote].voteCount += sender.weight; |
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proposals[delegate_.vote].voteCount += sender.weight; |
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} else { |
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// If the delegate did not vote yet, |
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// add to her weight. |
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delegate.weight += sender.weight; |
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delegate_.weight += sender.weight; |
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} |
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} |
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/// Give your vote (including votes delegated to you) |
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/// to proposal \`proposals[proposal].name\`. |
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function vote(uint proposal) { |
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Voter sender = voters[msg.sender]; |
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if (sender.voted) |
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throw; |
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/** |
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* @dev Give your vote (including votes delegated to you) to proposal 'proposals[proposal].name'. |
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* @param proposal index of proposal in the proposals array |
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*/ |
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function vote(uint proposal) public { |
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Voter storage sender = voters[msg.sender]; |
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require(sender.weight != 0, "Has no right to vote"); |
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require(!sender.voted, "Already voted."); |
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sender.voted = true; |
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sender.vote = proposal; |
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// If \`proposal\` is out of the range of the array, |
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// If 'proposal' is out of the range of the array, |
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// this will throw automatically and revert all |
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// changes. |
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proposals[proposal].voteCount += sender.weight; |
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} |
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/// @dev Computes the winning proposal taking all |
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/// previous votes into account. |
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function winningProposal() constant |
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returns (uint winningProposal) |
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/** |
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* @dev Computes the winning proposal taking all previous votes into account. |
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* @return winningProposal_ index of winning proposal in the proposals array |
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*/ |
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function winningProposal() public view |
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returns (uint winningProposal_) |
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{ |
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uint winningVoteCount = 0; |
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for (uint p = 0; p < proposals.length; p++) { |
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if (proposals[p].voteCount > winningVoteCount) { |
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winningVoteCount = proposals[p].voteCount; |
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winningProposal = p; |
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winningProposal_ = p; |
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} |
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} |
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} |
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// Calls winningProposal() function to get the index |
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// of the winner contained in the proposals array and then |
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// returns the name of the winner |
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function winnerName() constant |
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returns (bytes32 winnerName) |
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/** |
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* @dev Calls winningProposal() function to get the index of the winner contained in the proposals array and then |
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* @return winnerName_ the name of the winner |
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*/ |
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function winnerName() public view |
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returns (bytes32 winnerName_) |
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{ |
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winnerName = proposals[winningProposal()].name; |
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winnerName_ = proposals[winningProposal()].name; |
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} |
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} |
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} |
bunsenstraat
2 years ago
committed by
GitHub