diff options
| -rw-r--r-- | docs/contracts.rst | 58 | ||||
| -rw-r--r-- | docs/frequently-asked-questions.rst | 52 | ||||
| -rw-r--r-- | docs/solidity-by-example.rst | 156 | ||||
| -rw-r--r-- | docs/structure-of-a-contract.rst | 2 | ||||
| -rw-r--r-- | docs/style-guide.rst | 24 | ||||
| -rw-r--r-- | docs/types.rst | 6 |
6 files changed, 208 insertions, 90 deletions
diff --git a/docs/contracts.rst b/docs/contracts.rst index 9923b1d2..68905fa4 100644 --- a/docs/contracts.rst +++ b/docs/contracts.rst @@ -67,6 +67,7 @@ This means that cyclic creation dependencies are impossible. TokenCreator creator; address owner; bytes32 name; + // This is the constructor which registers the // creator and the assigned name. function OwnedToken(bytes32 _name) { @@ -78,12 +79,14 @@ This means that cyclic creation dependencies are impossible. creator = TokenCreator(msg.sender); name = _name; } + function changeName(bytes32 newName) { // Only the creator can alter the name -- // the comparison is possible since contracts // are implicitly convertible to addresses. if (msg.sender == creator) name = newName; } + function transfer(address newOwner) { // Only the current owner can transfer the token. if (msg.sender != owner) return; @@ -107,11 +110,13 @@ This means that cyclic creation dependencies are impossible. // the ABI. return new OwnedToken(name); } + function changeName(OwnedToken tokenAddress, bytes32 name) { // Again, the external type of "tokenAddress" is // simply "address". tokenAddress.changeName(name); } + function isTokenTransferOK( address currentOwner, address newOwner @@ -222,8 +227,7 @@ The next example is a bit more complex: It will generate a function of the following form:: - function data(uint arg1, bool arg2, uint arg3) returns (uint a, bytes3 b) - { + function data(uint arg1, bool arg2, uint arg3) returns (uint a, bytes3 b) { a = data[arg1][arg2][arg3].a; b = data[arg1][arg2][arg3].b; } @@ -258,6 +262,8 @@ inheritable properties of contracts and may be overridden by derived contracts. // thrown. modifier onlyowner { if (msg.sender != owner) throw; _ } } + + contract mortal is owned { // This contract inherits the "onlyowner"-modifier from // "owned" and applies it to the "close"-function, which @@ -267,10 +273,14 @@ inheritable properties of contracts and may be overridden by derived contracts. selfdestruct(owner); } } + + contract priced { // Modifiers can receive arguments: modifier costs(uint price) { if (msg.value >= price) _ } } + + contract Register is priced, owned { mapping (address => bool) registeredAddresses; uint price; @@ -339,13 +349,15 @@ possible. uint x; } + // This contract rejects any Ether sent to it. It is good // practise to include such a function for every contract - // in order not to loose Ether. + // in order not to lose Ether. contract Rejector { function() { throw; } } + contract Caller { function callTest(address testAddress) { Test(testAddress).call(0xabcdef01); // hash does not exist @@ -406,6 +418,7 @@ All non-indexed arguments will be stored in the data part of the log. bytes32 indexed _id, uint _value ); + function deposit(bytes32 _id) { // Any call to this function (even deeply nested) can // be detected from the JavaScript API by filtering @@ -497,6 +510,7 @@ Details are given in the following example. address owner; } + // Use "is" to derive from another contract. Derived // contracts can access all non-private members including // internal functions and state variables. These cannot be @@ -507,6 +521,7 @@ Details are given in the following example. } } + // These abstract contracts are only provided to make the // interface known to the compiler. Note the function // without body. If a contract does not implement all @@ -514,11 +529,14 @@ Details are given in the following example. contract Config { function lookup(uint id) returns (address adr); } + + contract NameReg { function register(bytes32 name); function unregister(); } + // Multiple inheritance is possible. Note that "owned" is // also a base class of "mortal", yet there is only a single // instance of "owned" (as for virtual inheritance in C++). @@ -542,6 +560,7 @@ Details are given in the following example. } } + // If a constructor takes an argument, it needs to be // provided in the header (or modifier-invocation-style at // the constructor of the derived contract (see below)). @@ -564,12 +583,18 @@ seen in the following example:: if (msg.sender == owner) selfdestruct(owner); } } + + contract Base1 is mortal { function kill() { /* do cleanup 1 */ mortal.kill(); } } + + contract Base2 is mortal { function kill() { /* do cleanup 2 */ mortal.kill(); } } + + contract Final is Base1, Base2 { } @@ -583,12 +608,18 @@ derived override, but this function will bypass if (msg.sender == owner) selfdestruct(owner); } } + + contract Base1 is mortal { function kill() { /* do cleanup 1 */ super.kill(); } } + + contract Base2 is mortal { function kill() { /* do cleanup 2 */ super.kill(); } } + + contract Final is Base2, Base1 { } @@ -615,6 +646,8 @@ the base constructors. This can be done at two places:: uint x; function Base(uint _x) { x = _x; } } + + contract Derived is Base(7) { function Derived(uint _y) Base(_y * _y) { } @@ -721,6 +754,7 @@ more advanced example to implement a set). // We define a new struct datatype that will be used to // hold its data in the calling contract. struct Data { mapping(uint => bool) flags; } + // Note that the first parameter is of type "storage // reference" and thus only its storage address and not // its contents is passed as part of the call. This is a @@ -735,6 +769,7 @@ more advanced example to implement a set). self.flags[value] = true; return true; } + function remove(Data storage self, uint value) returns (bool) { @@ -743,14 +778,18 @@ more advanced example to implement a set). self.flags[value] = false; return true; } + function contains(Data storage self, uint value) returns (bool) { return self.flags[value]; } } + + contract C { Set.Data knownValues; + function register(uint value) { // The library functions can be called without a // specific instance of the library, since the @@ -783,12 +822,14 @@ custom types without the overhead of external function calls: library bigint { struct bigint { - uint[] limbs; + uint[] limbs; } + function fromUint(uint x) internal returns (bigint r) { r.limbs = new uint[](1); r.limbs[0] = x; } + function add(bigint _a, bigint _b) internal returns (bigint r) { r.limbs = new uint[](max(_a.limbs.length, _b.limbs.length)); uint carry = 0; @@ -820,6 +861,7 @@ custom types without the overhead of external function calls: } } + contract C { using bigint for bigint.bigint; function f() { @@ -882,6 +924,7 @@ Let us rewrite the set example from the // This is the same code as before, just without comments library Set { struct Data { mapping(uint => bool) flags; } + function insert(Data storage self, uint value) returns (bool) { @@ -890,6 +933,7 @@ Let us rewrite the set example from the self.flags[value] = true; return true; } + function remove(Data storage self, uint value) returns (bool) { @@ -898,6 +942,7 @@ Let us rewrite the set example from the self.flags[value] = false; return true; } + function contains(Data storage self, uint value) returns (bool) { @@ -905,9 +950,11 @@ Let us rewrite the set example from the } } + contract C { using Set for Set.Data; // this is the crucial change Set.Data knownValues; + function register(uint value) { // Here, all variables of type Set.Data have // corresponding member functions. @@ -928,12 +975,15 @@ It is also possible to extend elementary types in that way:: } } + contract C { using Search for uint[]; uint[] data; + function append(uint value) { data.push(value); } + function replace(uint _old, uint _new) { // This performs the library function call uint index = data.find(_old); diff --git a/docs/frequently-asked-questions.rst b/docs/frequently-asked-questions.rst index fc7d7b7f..ea8b6a67 100644 --- a/docs/frequently-asked-questions.rst +++ b/docs/frequently-asked-questions.rst @@ -24,7 +24,7 @@ Solidity contracts can be compiled a few different ways (see below) and the resulting output can be cut/pasted into a geth console to deploy them to the Ethereum blockchain. -There are some `contract examples <https://github.com/fivedogit/solidity-baby-steps/tree/master/contracts/>`_ by fivedogit and +There are some `contract examples <https://github.com/fivedogit/solidity-baby-steps/tree/master/contracts/>`_ by fivedogit and there should be a `test contract <https://github.com/ethereum/solidity/blob/develop/test/libsolidity/SolidityEndToEndTest.cpp>`_ for every single feature of Solidity. How do I compile contracts? @@ -76,7 +76,7 @@ Does selfdestruct() free up space in the blockchain? It removes the contract bytecode and storage from the current block into the future, but since the blockchain stores every single block (i.e. -all history), this will not actually free up space on full/achive nodes. +all history), this will not actually free up space on full/archive nodes. Create a contract that can be killed and return funds ===================================================== @@ -85,7 +85,7 @@ First, a word of warning: Killing contracts sounds like a good idea, because "cl is always good, but as seen above, it does not really clean up. Furthermore, if Ether is sent to removed contracts, the Ether will be forever lost. -If you want to deactivate your contracts, rather **disable** them by changing some +If you want to deactivate your contracts, it is preferable to **disable** them by changing some internal state which causes all functions to throw. This will make it impossible to use the contract and ether sent to the contract will be returned automatically. @@ -184,7 +184,9 @@ An example of this would be:: uint someNumber; string someString; } + mapping(uint => mapping(string => myStruct)) myDynamicMapping; + function storeInMapping() { myDynamicMapping[1]["Foo"] = myStruct(2, "Bar"); } @@ -351,11 +353,17 @@ should be noted that you must declare them as static memory arrays. Examples:: contract C { - struct S { uint a; uint b; } + struct S { + uint a; + uint b; + } + S public x = S(1, 2); string name = "Ada"; string[4] memory AdaArr = ["This", "is", "an", "array"]; } + + contract D { C c = new C(); } @@ -405,9 +413,11 @@ you should always convert it to a `bytes` first:: contract C { string s; + function append(byte c) { bytes(s).push(c); } + function set(uint i, byte c) { bytes(s)[i] = c; } @@ -448,15 +458,21 @@ If you do not want to throw, you can return a pair:: contract C { uint[] counters; + function getCounter(uint index) returns (uint counter, bool error) { if (index >= counters.length) return (0, true); else return (counters[index], false); - } + } + function checkCounter(uint index) { var (counter, error) = getCounter(index); - if (error) { ... } - else { ... } + if (error) { + ... + } + else { + ... + } } } @@ -515,12 +531,15 @@ Example:: contract C { uint[] data1; uint[] data2; + function appendOne() { append(data1); } + function appendTwo() { append(data2); } + function append(uint[] storage d) { d.push(1); } @@ -542,6 +561,7 @@ be created in memory, although it will be created in storage:: contract C { uint someVariable; uint[] data; + function f() { uint[] x; x.push(2); @@ -565,6 +585,7 @@ The correct way to do this is the following:: contract C { uint someVariable; uint[] data; + function f() { uint[] x = data; x.push(2); @@ -674,6 +695,7 @@ This is a very interesting question. Suppose that we have a contract field set u struct user{ mapping(string => address) usedContracts; } + function somefunction{ user user1; user1.usedContracts["Hello"] = "World"; @@ -694,6 +716,7 @@ In this example:: contract B {} contract A { address child; + function test() { child = (new B).value(10)(); //construct a new B with 10 wei } @@ -735,16 +758,20 @@ independent copies will be created:: contract C { uint[20] x; + function f() { g(x); h(x); } + function g(uint[20] y) { y[2] = 3; } + function h(uint[20] storage y) { y[3] = 4; } + } The call to `g(x)` will not have an effect on `x` because it needs to create an independent copy of the storage value in memory @@ -765,10 +792,10 @@ contract level) with `arrayname.length = <some new length>;`. If you get the :: - int8[] memory memArr; // Case 1 - memArr.length++; // illegal - int8[5] storageArr; // Case 2 - somearray.length++; // legal + int8[] memory memArr; // Case 1 + memArr.length++; // illegal + int8[5] storageArr; // Case 2 + somearray.length++; // legal int8[5] storage storageArr2; // Explicit case 2 somearray2.length++; // legal @@ -821,7 +848,8 @@ What does the following strange check do in the Custom Token contract? :: - if (balanceOf[_to] + _value < balanceOf[_to]) throw; + if (balanceOf[_to] + _value < balanceOf[_to]) + throw; Integers in Solidity (and most other machine-related programming languages) are restricted to a certain range. For `uint256`, this is `0` up to `2**256 - 1`. If the result of some operation on those numbers diff --git a/docs/solidity-by-example.rst b/docs/solidity-by-example.rst index 59400f3f..171e9273 100644 --- a/docs/solidity-by-example.rst +++ b/docs/solidity-by-example.rst @@ -39,18 +39,17 @@ of votes. :: /// @title Voting with delegation. - contract Ballot - { + contract Ballot { // This declares a new complex type which will // be used for variables later. // It will represent a single voter. - struct Voter - { + struct Voter { uint weight; // weight is accumulated by delegation bool voted; // if true, that person already voted address delegate; // person delegated to uint vote; // index of the voted proposal } + // This is a type for a single proposal. struct Proposal { @@ -59,21 +58,23 @@ of votes. } address public chairperson; + // This declares a state variable that // stores a `Voter` struct for each possible address. mapping(address => Voter) public voters; + // A dynamically-sized array of `Proposal` structs. Proposal[] public proposals; /// Create a new ballot to choose one of `proposalNames`. - function Ballot(bytes32[] proposalNames) - { + function Ballot(bytes32[] proposalNames) { chairperson = msg.sender; voters[chairperson].weight = 1; + // For each of the provided proposal names, // create a new proposal object and add it // to the end of the array. - for (uint i = 0; i < proposalNames.length; i++) + for (uint i = 0; i < proposalNames.length; i++) { // `Proposal({...})` creates a temporary // Proposal object and `proposal.push(...)` // appends it to the end of `proposals`. @@ -81,60 +82,68 @@ of votes. name: proposalNames[i], voteCount: 0 })); + } } // Give `voter` the right to vote on this ballot. // May only be called by `chairperson`. - function giveRightToVote(address voter) - { - if (msg.sender != chairperson || voters[voter].voted) + function giveRightToVote(address voter) { + if (msg.sender != chairperson || voters[voter].voted) { // `throw` terminates and reverts all changes to // the state and to Ether balances. It is often // a good idea to use this if functions are // called incorrectly. But watch out, this // will also consume all provided gas. throw; + } voters[voter].weight = 1; } /// Delegate your vote to the voter `to`. - function delegate(address to) - { + function delegate(address to) { // assigns reference Voter sender = voters[msg.sender]; if (sender.voted) throw; + // Forward the delegation as long as // `to` also delegated. while (voters[to].delegate != address(0) && - voters[to].delegate != msg.sender) - to = voters[to].delegate; + voters[to].delegate != msg.sender) { + to = voters[to].delegate; + } + // We found a loop in the delegation, not allowed. - if (to == msg.sender) + if (to == msg.sender) { throw; + } + // Since `sender` is a reference, this // modifies `voters[msg.sender].voted` sender.voted = true; sender.delegate = to; Voter delegate = voters[to]; - if (delegate.voted) + if (delegate.voted) { // If the delegate already voted, // directly add to the number of votes proposals[delegate.vote].voteCount += sender.weight; - else + } + else { // If the delegate did not vote yet, // add to her weight. delegate.weight += sender.weight; + } } /// Give your vote (including votes delegated to you) /// to proposal `proposals[proposal].name`. - function vote(uint proposal) - { + function vote(uint proposal) { Voter sender = voters[msg.sender]; - if (sender.voted) throw; + if (sender.voted) + throw; sender.voted = true; sender.vote = proposal; + // If `proposal` is out of the range of the array, // this will throw automatically and revert all // changes. @@ -147,10 +156,8 @@ of votes. returns (uint winningProposal) { uint winningVoteCount = 0; - for (uint p = 0; p < proposals.length; p++) - { - if (proposals[p].voteCount > winningVoteCount) - { + for (uint p = 0; p < proposals.length; p++) { + if (proposals[p].voteCount > winningVoteCount) { winningVoteCount = proposals[p].voteCount; winningProposal = p; } @@ -223,8 +230,10 @@ activate themselves. /// Create a simple auction with `_biddingTime` /// seconds bidding time on behalf of the /// beneficiary address `_beneficiary`. - function SimpleAuction(uint _biddingTime, - address _beneficiary) { + function SimpleAuction( + uint _biddingTime, + address _beneficiary + ) { beneficiary = _beneficiary; auctionStart = now; biddingTime = _biddingTime; @@ -238,16 +247,19 @@ activate themselves. // No arguments are necessary, all // information is already part of // the transaction. - if (now > auctionStart + biddingTime) + if (now > auctionStart + biddingTime) { // Revert the call if the bidding // period is over. throw; - if (msg.value <= highestBid) + } + if (msg.value <= highestBid) { // If the bid is not higher, send the // money back. throw; - if (highestBidder != 0) + } + if (highestBidder != 0) { highestBidder.send(highestBid); + } highestBidder = msg.sender; highestBid = msg.value; HighestBidIncreased(msg.sender, msg.value); @@ -261,6 +273,7 @@ activate themselves. if (ended) throw; // this function has already been called AuctionEnded(highestBidder, highestBid); + // We send all the money we have, because some // of the refunds might have failed. beneficiary.send(this.balance); @@ -319,13 +332,12 @@ high or low invalid bids. :: - contract BlindAuction - { - struct Bid - { + contract BlindAuction { + struct Bid { bytes32 blindedBid; uint deposit; } + address public beneficiary; uint public auctionStart; uint public biddingEnd; @@ -346,10 +358,11 @@ high or low invalid bids. modifier onlyBefore(uint _time) { if (now >= _time) throw; _ } modifier onlyAfter(uint _time) { if (now <= _time) throw; _ } - function BlindAuction(uint _biddingTime, - uint _revealTime, - address _beneficiary) - { + function BlindAuction( + uint _biddingTime, + uint _revealTime, + address _beneficiary + ) { beneficiary = _beneficiary; auctionStart = now; biddingEnd = now + _biddingTime; @@ -377,29 +390,38 @@ high or low invalid bids. /// Reveal your blinded bids. You will get a refund for all /// correctly blinded invalid bids and for all bids except for /// the totally highest. - function reveal(uint[] _values, bool[] _fake, - bytes32[] _secret) + function reveal( + uint[] _values, + bool[] _fake, + bytes32[] _secret + ) onlyAfter(biddingEnd) onlyBefore(revealEnd) { uint length = bids[msg.sender].length; - if (_values.length != length || _fake.length != length || - _secret.length != length) + if ( + _values.length != length || + _fake.length != length || + _secret.length != length + ) { throw; + } + uint refund; - for (uint i = 0; i < length; i++) - { + for (uint i = 0; i < length; i++) { var bid = bids[msg.sender][i]; var (value, fake, secret) = (_values[i], _fake[i], _secret[i]); - if (bid.blindedBid != sha3(value, fake, secret)) + if (bid.blindedBid != sha3(value, fake, secret)) { // Bid was not actually revealed. // Do not refund deposit. continue; + } refund += bid.deposit; - if (!fake && bid.deposit >= value) + if (!fake && bid.deposit >= value) { if (placeBid(msg.sender, value)) refund -= value; + } // Make it impossible for the sender to re-claim // the same deposit. bid.blindedBid = 0; @@ -413,11 +435,13 @@ high or low invalid bids. function placeBid(address bidder, uint value) internal returns (bool success) { - if (value <= highestBid) + if (value <= highestBid) { return false; - if (highestBidder != 0) + } + if (highestBidder != 0) { // Refund the previously highest bidder. highestBidder.send(highestBid); + } highestBid = value; highestBidder = bidder; return true; @@ -428,7 +452,8 @@ high or low invalid bids. function auctionEnd() onlyAfter(revealEnd) { - if (ended) throw; + if (ended) + throw; AuctionEnded(highestBidder, highestBid); // We send all the money we have, because some // of the refunds might have failed. @@ -436,7 +461,9 @@ high or low invalid bids. ended = true; } - function () { throw; } + function () { + throw; + } } .. index:: purchase, remote purchase, escrow @@ -449,39 +476,39 @@ Safe Remote Purchase :: - contract Purchase - { + contract Purchase { uint public value; address public seller; address public buyer; enum State { Created, Locked, Inactive } State public state; - function Purchase() - { + + function Purchase() { seller = msg.sender; value = msg.value / 2; if (2 * value != msg.value) throw; } - modifier require(bool _condition) - { + + modifier require(bool _condition) { if (!_condition) throw; _ } - modifier onlyBuyer() - { + + modifier onlyBuyer() { if (msg.sender != buyer) throw; _ } - modifier onlySeller() - { + + modifier onlySeller() { if (msg.sender != seller) throw; _ } - modifier inState(State _state) - { + + modifier inState(State _state) { if (state != _state) throw; _ } + event aborted(); event purchaseConfirmed(); event itemReceived(); @@ -497,6 +524,7 @@ Safe Remote Purchase seller.send(this.balance); state = State.Inactive; } + /// Confirm the purchase as buyer. /// Transaction has to include `2 * value` ether. /// The ether will be locked until confirmReceived @@ -509,6 +537,7 @@ Safe Remote Purchase buyer = msg.sender; state = State.Locked; } + /// Confirm that you (the buyer) received the item. /// This will release the locked ether. function confirmReceived() @@ -520,7 +549,10 @@ Safe Remote Purchase seller.send(this.balance); state = State.Inactive; } - function() { throw; } + + function() { + throw; + } } ******************** diff --git a/docs/structure-of-a-contract.rst b/docs/structure-of-a-contract.rst index 2e121847..0968ffc8 100644 --- a/docs/structure-of-a-contract.rst +++ b/docs/structure-of-a-contract.rst @@ -80,7 +80,7 @@ Events are convenience interfaces with the EVM logging facilities. :: - contract SimpleAuction { + contract SimpleAuction { event HighestBidIncreased(address bidder, uint amount); // Event function bid() { diff --git a/docs/style-guide.rst b/docs/style-guide.rst index c36efe2c..bc32f891 100644 --- a/docs/style-guide.rst +++ b/docs/style-guide.rst @@ -25,7 +25,7 @@ solidity code. The goal of this guide is *consistency*. A quote from python's captures this concept well. A style guide is about consistency. Consistency with this style guide is important. Consistency within a project is more important. Consistency within one module or function is most important. - But most importantly: know when to be inconsistent -- sometimes the style guide just doesn't apply. When in doubt, use your best judgment. Look at other examples and decide what looks best. And don't hesitate to ask! + But most importantly: know when to be inconsistent -- sometimes the style guide just doesn't apply. When in doubt, use your best judgment. Look at other examples and decide what looks best. And don't hesitate to ask! *********** @@ -155,19 +155,27 @@ Whitespace in Expressions Avoid extraneous whitespace in the following situations: -* Immediately inside parenthesis, brackets or braces. +Immediately inside parenthesis, brackets or braces. -Yes: `spam(ham[1], Coin({name: "ham"}));` +Yes:: + + spam(ham[1], Coin({name: "ham"})); + +No:: -No: `spam( ham[ 1 ], Coin( { name: "ham" } ) );` + spam( ham[ 1 ], Coin( { name: "ham" } ) );` -* Immediately before a comma, semicolon: +Immediately before a comma, semicolon: -Yes: `function spam(uint i, Coin coin);` +Yes:: + + function spam(uint i, Coin coin); + +No:: -No: `function spam(uint i , Coin coin) ;` + function spam(uint i , Coin coin) ; -* More than one space around an assignment or other operator to align with +More than one space around an assignment or other operator to align with another: Yes:: diff --git a/docs/types.rst b/docs/types.rst index 187f62c1..0ec57afc 100644 --- a/docs/types.rst +++ b/docs/types.rst @@ -43,7 +43,7 @@ The operators `||` and `&&` apply the common short-circuiting rules. This means Integers -------- -`int•` / `uint•`: Signed and unsigned integers of various sizes. Keywords `uint8` to `uint256` in steps of `8` (unsigned of 8 up to 256 bits) and `int8` to `int256`. `uint` and `int` are aliases for `uint256` and `int256`, respectively. +`int` / `uint`: Signed and unsigned integers of various sizes. Keywords `uint8` to `uint256` in steps of `8` (unsigned of 8 up to 256 bits) and `int8` to `int256`. `uint` and `int` are aliases for `uint256` and `int256`, respectively. Operators: @@ -59,7 +59,7 @@ operators are :ref:`literals<integer_literals>` (or literal expressions). Address ------- -`address`: Holds a 20 byte value (size of an Ethereum address). Address types also have members(see [Functions on addresses](#functions-on-addresses)) and serve as base for all contracts. +`address`: Holds a 20 byte value (size of an Ethereum address). Address types also have members and serve as base for all contracts. Operators: @@ -153,7 +153,7 @@ It is even possible to temporarily exceed the maximum of 256 bits as long as onl String Literals --------------- -String Literals are written with double quotes (`"abc"`). As with integer literals, their type can vary, but they are implicitly convertible to `bytes•` if they fit, to `bytes` and to `string`. +String Literals are written with double quotes (`"abc"`). As with integer literals, their type can vary, but they are implicitly convertible to `bytes` if they fit, to `bytes` and to `string`. .. index:: enum |