Add real-world examples from https://blog.sigmaprime.io/solidity-security.html

solidity_examples/BECToken.sol

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+pragma solidity ^0.4.16;
+
+/**
+ * @title SafeMath
+ * @dev Math operations with safety checks that throw on error
+ */
+library SafeMath {
+  function mul(uint256 a, uint256 b) internal constant returns (uint256) {
+    uint256 c = a * b;
+    assert(a == 0 || c / a == b);
+    return c;
+  }
+
+  function div(uint256 a, uint256 b) internal constant returns (uint256) {
+    // assert(b > 0); // Solidity automatically throws when dividing by 0
+    uint256 c = a / b;
+    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
+    return c;
+  }
+
+  function sub(uint256 a, uint256 b) internal constant returns (uint256) {
+    assert(b <= a);
+    return a - b;
+  }
+
+  function add(uint256 a, uint256 b) internal constant returns (uint256) {
+    uint256 c = a + b;
+    assert(c >= a);
+    return c;
+  }
+}
+
+/**
+ * @title ERC20Basic
+ * @dev Simpler version of ERC20 interface
+ * @dev see https://github.com/ethereum/EIPs/issues/179
+ */
+contract ERC20Basic {
+  uint256 public totalSupply;
+  function balanceOf(address who) public constant returns (uint256);
+  function transfer(address to, uint256 value) public returns (bool);
+  event Transfer(address indexed from, address indexed to, uint256 value);
+}
+
+/**
+ * @title Basic token
+ * @dev Basic version of StandardToken, with no allowances.
+ */
+contract BasicToken is ERC20Basic {
+  using SafeMath for uint256;
+
+  mapping(address => uint256) balances;
+
+  /**
+  * @dev transfer token for a specified address
+  * @param _to The address to transfer to.
+  * @param _value The amount to be transferred.
+  */
+  function transfer(address _to, uint256 _value) public returns (bool) {
+    require(_to != address(0));
+    require(_value > 0 && _value <= balances[msg.sender]);
+
+    // SafeMath.sub will throw if there is not enough balance.
+    balances[msg.sender] = balances[msg.sender].sub(_value);
+    balances[_to] = balances[_to].add(_value);
+    Transfer(msg.sender, _to, _value);
+    return true;
+  }
+
+  /**
+  * @dev Gets the balance of the specified address.
+  * @param _owner The address to query the the balance of.
+  * @return An uint256 representing the amount owned by the passed address.
+  */
+  function balanceOf(address _owner) public constant returns (uint256 balance) {
+    return balances[_owner];
+  }
+}
+
+/**
+ * @title ERC20 interface
+ * @dev see https://github.com/ethereum/EIPs/issues/20
+ */
+contract ERC20 is ERC20Basic {
+  function allowance(address owner, address spender) public constant returns (uint256);
+  function transferFrom(address from, address to, uint256 value) public returns (bool);
+  function approve(address spender, uint256 value) public returns (bool);
+  event Approval(address indexed owner, address indexed spender, uint256 value);
+}
+
+
+/**
+ * @title Standard ERC20 token
+ *
+ * @dev Implementation of the basic standard token.
+ * @dev https://github.com/ethereum/EIPs/issues/20
+ * @dev Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
+ */
+contract StandardToken is ERC20, BasicToken {
+
+  mapping (address => mapping (address => uint256)) internal allowed;
+
+
+  /**
+   * @dev Transfer tokens from one address to another
+   * @param _from address The address which you want to send tokens from
+   * @param _to address The address which you want to transfer to
+   * @param _value uint256 the amount of tokens to be transferred
+   */
+  function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
+    require(_to != address(0));
+    require(_value > 0 && _value <= balances[_from]);
+    require(_value <= allowed[_from][msg.sender]);
+
+    balances[_from] = balances[_from].sub(_value);
+    balances[_to] = balances[_to].add(_value);
+    allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
+    Transfer(_from, _to, _value);
+    return true;
+  }
+
+  /**
+   * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
+   *
+   * Beware that changing an allowance with this method brings the risk that someone may use both the old
+   * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
+   * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
+   * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
+   * @param _spender The address which will spend the funds.
+   * @param _value The amount of tokens to be spent.
+   */
+  function approve(address _spender, uint256 _value) public returns (bool) {
+    allowed[msg.sender][_spender] = _value;
+    Approval(msg.sender, _spender, _value);
+    return true;
+  }
+
+  /**
+   * @dev Function to check the amount of tokens that an owner allowed to a spender.
+   * @param _owner address The address which owns the funds.
+   * @param _spender address The address which will spend the funds.
+   * @return A uint256 specifying the amount of tokens still available for the spender.
+   */
+  function allowance(address _owner, address _spender) public constant returns (uint256 remaining) {
+    return allowed[_owner][_spender];
+  }
+}
+
+/**
+ * @title Ownable
+ * @dev The Ownable contract has an owner address, and provides basic authorization control
+ * functions, this simplifies the implementation of "user permissions".
+ */
+contract Ownable {
+  address public owner;
+
+
+  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
+
+
+  /**
+   * @dev The Ownable constructor sets the original `owner` of the contract to the sender
+   * account.
+   */
+  function Ownable() {
+    owner = msg.sender;
+  }
+
+
+  /**
+   * @dev Throws if called by any account other than the owner.
+   */
+  modifier onlyOwner() {
+    require(msg.sender == owner);
+    _;
+  }
+
+
+  /**
+   * @dev Allows the current owner to transfer control of the contract to a newOwner.
+   * @param newOwner The address to transfer ownership to.
+   */
+  function transferOwnership(address newOwner) onlyOwner public {
+    require(newOwner != address(0));
+    OwnershipTransferred(owner, newOwner);
+    owner = newOwner;
+  }
+
+}
+
+/**
+ * @title Pausable
+ * @dev Base contract which allows children to implement an emergency stop mechanism.
+ */
+contract Pausable is Ownable {
+  event Pause();
+  event Unpause();
+
+  bool public paused = false;
+
+
+  /**
+   * @dev Modifier to make a function callable only when the contract is not paused.
+   */
+  modifier whenNotPaused() {
+    require(!paused);
+    _;
+  }
+
+  /**
+   * @dev Modifier to make a function callable only when the contract is paused.
+   */
+  modifier whenPaused() {
+    require(paused);
+    _;
+  }
+
+  /**
+   * @dev called by the owner to pause, triggers stopped state
+   */
+  function pause() onlyOwner whenNotPaused public {
+    paused = true;
+    Pause();
+  }
+
+  /**
+   * @dev called by the owner to unpause, returns to normal state
+   */
+  function unpause() onlyOwner whenPaused public {
+    paused = false;
+    Unpause();
+  }
+}
+
+/**
+ * @title Pausable token
+ *
+ * @dev StandardToken modified with pausable transfers.
+ **/
+
+contract PausableToken is StandardToken, Pausable {
+
+  function transfer(address _to, uint256 _value) public whenNotPaused returns (bool) {
+    return super.transfer(_to, _value);
+  }
+
+  function transferFrom(address _from, address _to, uint256 _value) public whenNotPaused returns (bool) {
+    return super.transferFrom(_from, _to, _value);
+  }
+
+  function approve(address _spender, uint256 _value) public whenNotPaused returns (bool) {
+    return super.approve(_spender, _value);
+  }
+  
+  function batchTransfer(address[] _receivers, uint256 _value) public whenNotPaused returns (bool) {
+    uint cnt = _receivers.length;
+    uint256 amount = uint256(cnt) * _value;
+    require(cnt > 0 && cnt <= 20);
+    require(_value > 0 && balances[msg.sender] >= amount);
+
+    balances[msg.sender] = balances[msg.sender].sub(amount);
+    for (uint i = 0; i < cnt; i++) {
+        balances[_receivers[i]] = balances[_receivers[i]].add(_value);
+        Transfer(msg.sender, _receivers[i], _value);
+    }
+    return true;
+  }
+}
+
+/**
+ * @title Bec Token
+ *
+ * @dev Implementation of Bec Token based on the basic standard token.
+ */
+contract BecToken is PausableToken {
+    /**
+    * Public variables of the token
+    * The following variables are OPTIONAL vanities. One does not have to include them.
+    * They allow one to customise the token contract & in no way influences the core functionality.
+    * Some wallets/interfaces might not even bother to look at this information.
+    */
+    string public name = "BeautyChain";
+    string public symbol = "BEC";
+    string public version = '1.0.0';
+    uint8 public decimals = 18;
+
+    /**
+     * @dev Function to check the amount of tokens that an owner allowed to a spender.
+     */
+    function BecToken() {
+      totalSupply = 7000000000 * (10**(uint256(decimals)));
+      balances[msg.sender] = totalSupply;    // Give the creator all initial tokens
+    }
+
+    function () {
+        //if ether is sent to this address, send it back.
+        revert();
+    }
+}

solidity_examples/WalletLibrary.sol

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+//sol Wallet
+// Multi-sig, daily-limited account proxy/wallet.
+// @authors:
+// Gav Wood <g@ethdev.com>
+// inheritable "property" contract that enables methods to be protected by requiring the acquiescence of either a
+// single, or, crucially, each of a number of, designated owners.
+// usage:
+// use modifiers onlyowner (just own owned) or onlymanyowners(hash), whereby the same hash must be provided by
+// some number (specified in constructor) of the set of owners (specified in the constructor, modifiable) before the
+// interior is executed.
+
+pragma solidity ^0.4.9;
+
+contract WalletEvents {
+  // EVENTS
+
+  // this contract only has six types of events: it can accept a confirmation, in which case
+  // we record owner and operation (hash) alongside it.
+  event Confirmation(address owner, bytes32 operation);
+  event Revoke(address owner, bytes32 operation);
+
+  // some others are in the case of an owner changing.
+  event OwnerChanged(address oldOwner, address newOwner);
+  event OwnerAdded(address newOwner);
+  event OwnerRemoved(address oldOwner);
+
+  // the last one is emitted if the required signatures change
+  event RequirementChanged(uint newRequirement);
+
+  // Funds has arrived into the wallet (record how much).
+  event Deposit(address _from, uint value);
+  // Single transaction going out of the wallet (record who signed for it, how much, and to whom it's going).
+  event SingleTransact(address owner, uint value, address to, bytes data, address created);
+  // Multi-sig transaction going out of the wallet (record who signed for it last, the operation hash, how much, and to whom it's going).
+  event MultiTransact(address owner, bytes32 operation, uint value, address to, bytes data, address created);
+  // Confirmation still needed for a transaction.
+  event ConfirmationNeeded(bytes32 operation, address initiator, uint value, address to, bytes data);
+}
+
+contract WalletAbi {
+  // Revokes a prior confirmation of the given operation
+  function revoke(bytes32 _operation) external;
+
+  // Replaces an owner `_from` with another `_to`.
+  function changeOwner(address _from, address _to) external;
+
+  function addOwner(address _owner) external;
+
+  function removeOwner(address _owner) external;
+
+  function changeRequirement(uint _newRequired) external;
+
+  function isOwner(address _addr) constant returns (bool);
+
+  function hasConfirmed(bytes32 _operation, address _owner) external constant returns (bool);
+
+  // (re)sets the daily limit. needs many of the owners to confirm. doesn't alter the amount already spent today.
+  function setDailyLimit(uint _newLimit) external;
+
+  function execute(address _to, uint _value, bytes _data) external returns (bytes32 o_hash);
+  function confirm(bytes32 _h) returns (bool o_success);
+}
+
+contract WalletLibrary is WalletEvents {
+  // TYPES
+
+  // struct for the status of a pending operation.
+  struct PendingState {
+    uint yetNeeded;
+    uint ownersDone;
+    uint index;
+  }
+
+  // Transaction structure to remember details of transaction lest it need be saved for a later call.
+  struct Transaction {
+    address to;
+    uint value;
+    bytes data;
+  }
+
+  // MODIFIERS
+
+  // simple single-sig function modifier.
+  modifier onlyowner {
+    if (isOwner(msg.sender))
+      _;
+  }
+  // multi-sig function modifier: the operation must have an intrinsic hash in order
+  // that later attempts can be realised as the same underlying operation and
+  // thus count as confirmations.
+  modifier onlymanyowners(bytes32 _operation) {
+    if (confirmAndCheck(_operation))
+      _;
+  }
+
+  // METHODS
+
+  // gets called when no other function matches
+  function() payable {
+    // just being sent some cash?
+    if (msg.value > 0)
+      Deposit(msg.sender, msg.value);
+  }
+
+  // constructor is given number of sigs required to do protected "onlymanyowners" transactions
+  // as well as the selection of addresses capable of confirming them.
+  function initMultiowned(address[] _owners, uint _required) only_uninitialized {
+    m_numOwners = _owners.length + 1;
+    m_owners[1] = uint(msg.sender);
+    m_ownerIndex[uint(msg.sender)] = 1;
+    for (uint i = 0; i < _owners.length; ++i)
+    {
+      m_owners[2 + i] = uint(_owners[i]);
+      m_ownerIndex[uint(_owners[i])] = 2 + i;
+    }
+    m_required = _required;
+  }
+
+  // Revokes a prior confirmation of the given operation
+  function revoke(bytes32 _operation) external {
+    uint ownerIndex = m_ownerIndex[uint(msg.sender)];
+    // make sure they're an owner
+    if (ownerIndex == 0) return;
+    uint ownerIndexBit = 2**ownerIndex;
+    var pending = m_pending[_operation];
+    if (pending.ownersDone & ownerIndexBit > 0) {
+      pending.yetNeeded++;
+      pending.ownersDone -= ownerIndexBit;
+      Revoke(msg.sender, _operation);
+    }
+  }
+
+  // Replaces an owner `_from` with another `_to`.
+  function changeOwner(address _from, address _to) onlymanyowners(sha3(msg.data)) external {
+    if (isOwner(_to)) return;
+    uint ownerIndex = m_ownerIndex[uint(_from)];
+    if (ownerIndex == 0) return;
+
+    clearPending();
+    m_owners[ownerIndex] = uint(_to);
+    m_ownerIndex[uint(_from)] = 0;
+    m_ownerIndex[uint(_to)] = ownerIndex;
+    OwnerChanged(_from, _to);
+  }
+
+  function addOwner(address _owner) onlymanyowners(sha3(msg.data)) external {
+    if (isOwner(_owner)) return;
+
+    clearPending();
+    if (m_numOwners >= c_maxOwners)
+      reorganizeOwners();
+    if (m_numOwners >= c_maxOwners)
+      return;
+    m_numOwners++;
+    m_owners[m_numOwners] = uint(_owner);
+    m_ownerIndex[uint(_owner)] = m_numOwners;
+    OwnerAdded(_owner);
+  }
+
+  function removeOwner(address _owner) onlymanyowners(sha3(msg.data)) external {
+    uint ownerIndex = m_ownerIndex[uint(_owner)];
+    if (ownerIndex == 0) return;
+    if (m_required > m_numOwners - 1) return;
+
+    m_owners[ownerIndex] = 0;
+    m_ownerIndex[uint(_owner)] = 0;
+    clearPending();
+    reorganizeOwners(); //make sure m_numOwner is equal to the number of owners and always points to the optimal free slot
+    OwnerRemoved(_owner);
+  }
+
+  function changeRequirement(uint _newRequired) onlymanyowners(sha3(msg.data)) external {
+    if (_newRequired > m_numOwners) return;
+    m_required = _newRequired;
+    clearPending();
+    RequirementChanged(_newRequired);
+  }
+
+  // Gets an owner by 0-indexed position (using numOwners as the count)
+  function getOwner(uint ownerIndex) external constant returns (address) {
+    return address(m_owners[ownerIndex + 1]);
+  }
+
+  function isOwner(address _addr) constant returns (bool) {
+    return m_ownerIndex[uint(_addr)] > 0;
+  }
+
+  function hasConfirmed(bytes32 _operation, address _owner) external constant returns (bool) {
+    var pending = m_pending[_operation];
+    uint ownerIndex = m_ownerIndex[uint(_owner)];
+
+    // make sure they're an owner
+    if (ownerIndex == 0) return false;
+
+    // determine the bit to set for this owner.
+    uint ownerIndexBit = 2**ownerIndex;
+    return !(pending.ownersDone & ownerIndexBit == 0);
+  }
+
+  // constructor - stores initial daily limit and records the present day's index.
+  function initDaylimit(uint _limit) only_uninitialized {
+    m_dailyLimit = _limit;
+    m_lastDay = today();
+  }
+  // (re)sets the daily limit. needs many of the owners to confirm. doesn't alter the amount already spent today.
+  function setDailyLimit(uint _newLimit) onlymanyowners(sha3(msg.data)) external {
+    m_dailyLimit = _newLimit;
+  }
+  // resets the amount already spent today. needs many of the owners to confirm.
+  function resetSpentToday() onlymanyowners(sha3(msg.data)) external {
+    m_spentToday = 0;
+  }
+
+  // throw unless the contract is not yet initialized.
+  modifier only_uninitialized { if (m_numOwners > 0) throw; _; }
+
+  // constructor - just pass on the owner array to the multiowned and
+  // the limit to daylimit
+  function initWallet(address[] _owners, uint _required, uint _daylimit) only_uninitialized {
+    initDaylimit(_daylimit);
+    initMultiowned(_owners, _required);
+  }
+
+  // kills the contract sending everything to `_to`.
+  function kill(address _to) onlymanyowners(sha3(msg.data)) external {
+    suicide(_to);
+  }
+
+  // Outside-visible transact entry point. Executes transaction immediately if below daily spend limit.
+  // If not, goes into multisig process. We provide a hash on return to allow the sender to provide
+  // shortcuts for the other confirmations (allowing them to avoid replicating the _to, _value
+  // and _data arguments). They still get the option of using them if they want, anyways.
+  function execute(address _to, uint _value, bytes _data) external onlyowner returns (bytes32 o_hash) {
+    // first, take the opportunity to check that we're under the daily limit.
+    if ((_data.length == 0 && underLimit(_value)) || m_required == 1) {
+      // yes - just execute the call.
+      address created;
+      if (_to == 0) {
+        created = create(_value, _data);
+      } else {
+        if (!_to.call.value(_value)(_data))
+          throw;
+      }
+      SingleTransact(msg.sender, _value, _to, _data, created);
+    } else {
+      // determine our operation hash.
+      o_hash = sha3(msg.data, block.number);
+      // store if it's new
+      if (m_txs[o_hash].to == 0 && m_txs[o_hash].value == 0 && m_txs[o_hash].data.length == 0) {
+        m_txs[o_hash].to = _to;
+        m_txs[o_hash].value = _value;
+        m_txs[o_hash].data = _data;
+      }
+      if (!confirm(o_hash)) {
+        ConfirmationNeeded(o_hash, msg.sender, _value, _to, _data);
+      }
+    }
+  }
+
+  function create(uint _value, bytes _code) internal returns (address o_addr) {
+    assembly {
+      o_addr := create(_value, add(_code, 0x20), mload(_code))
+      jumpi(0xdeadbeef, iszero(extcodesize(o_addr)))
+    }
+  }
+
+  // confirm a transaction through just the hash. we use the previous transactions map, m_txs, in order
+  // to determine the body of the transaction from the hash provided.
+  function confirm(bytes32 _h) onlymanyowners(_h) returns (bool o_success) {
+    if (m_txs[_h].to != 0 || m_txs[_h].value != 0 || m_txs[_h].data.length != 0) {
+      address created;
+      if (m_txs[_h].to == 0) {
+        created = create(m_txs[_h].value, m_txs[_h].data);
+      } else {
+        if (!m_txs[_h].to.call.value(m_txs[_h].value)(m_txs[_h].data))
+          throw;
+      }
+
+      MultiTransact(msg.sender, _h, m_txs[_h].value, m_txs[_h].to, m_txs[_h].data, created);
+      delete m_txs[_h];
+      return true;
+    }
+  }
+
+  // INTERNAL METHODS
+
+  function confirmAndCheck(bytes32 _operation) internal returns (bool) {
+    // determine what index the present sender is:
+    uint ownerIndex = m_ownerIndex[uint(msg.sender)];
+    // make sure they're an owner
+    if (ownerIndex == 0) return;
+
+    var pending = m_pending[_operation];
+    // if we're not yet working on this operation, switch over and reset the confirmation status.
+    if (pending.yetNeeded == 0) {
+      // reset count of confirmations needed.
+      pending.yetNeeded = m_required;
+      // reset which owners have confirmed (none) - set our bitmap to 0.
+      pending.ownersDone = 0;
+      pending.index = m_pendingIndex.length++;
+      m_pendingIndex[pending.index] = _operation;
+    }
+    // determine the bit to set for this owner.
+    uint ownerIndexBit = 2**ownerIndex;
+    // make sure we (the message sender) haven't confirmed this operation previously.
+    if (pending.ownersDone & ownerIndexBit == 0) {
+      Confirmation(msg.sender, _operation);
+      // ok - check if count is enough to go ahead.
+      if (pending.yetNeeded <= 1) {
+        // enough confirmations: reset and run interior.
+        delete m_pendingIndex[m_pending[_operation].index];
+        delete m_pending[_operation];
+        return true;
+      }
+      else
+      {
+        // not enough: record that this owner in particular confirmed.
+        pending.yetNeeded--;
+        pending.ownersDone |= ownerIndexBit;
+      }
+    }
+  }
+
+  function reorganizeOwners() private {
+    uint free = 1;
+    while (free < m_numOwners)
+    {
+      while (free < m_numOwners && m_owners[free] != 0) free++;
+      while (m_numOwners > 1 && m_owners[m_numOwners] == 0) m_numOwners--;
+      if (free < m_numOwners && m_owners[m_numOwners] != 0 && m_owners[free] == 0)
+      {
+        m_owners[free] = m_owners[m_numOwners];
+        m_ownerIndex[m_owners[free]] = free;
+        m_owners[m_numOwners] = 0;
+      }
+    }
+  }
+
+  // checks to see if there is at least `_value` left from the daily limit today. if there is, subtracts it and
+  // returns true. otherwise just returns false.
+  function underLimit(uint _value) internal onlyowner returns (bool) {
+    // reset the spend limit if we're on a different day to last time.
+    if (today() > m_lastDay) {
+      m_spentToday = 0;
+      m_lastDay = today();
+    }
+    // check to see if there's enough left - if so, subtract and return true.
+    // overflow protection                    // dailyLimit check
+    if (m_spentToday + _value >= m_spentToday && m_spentToday + _value <= m_dailyLimit) {
+      m_spentToday += _value;
+      return true;
+    }
+    return false;
+  }
+
+  // determines today's index.
+  function today() private constant returns (uint) { return now / 1 days; }
+
+  function clearPending() internal {
+    uint length = m_pendingIndex.length;
+
+    for (uint i = 0; i < length; ++i) {
+      delete m_txs[m_pendingIndex[i]];
+
+      if (m_pendingIndex[i] != 0)
+        delete m_pending[m_pendingIndex[i]];
+    }
+
+    delete m_pendingIndex;
+  }
+
+  // FIELDS
+  address constant _walletLibrary = 0xcafecafecafecafecafecafecafecafecafecafe;
+
+  // the number of owners that must confirm the same operation before it is run.
+  uint public m_required;
+  // pointer used to find a free slot in m_owners
+  uint public m_numOwners;
+
+  uint public m_dailyLimit;
+  uint public m_spentToday;
+  uint public m_lastDay;
+
+  // list of owners
+  uint[256] m_owners;
+
+  uint constant c_maxOwners = 250;
+  // index on the list of owners to allow reverse lookup
+  mapping(uint => uint) m_ownerIndex;
+  // the ongoing operations.
+  mapping(bytes32 => PendingState) m_pending;
+  bytes32[] m_pendingIndex;
+
+  // pending transactions we have at present.
+  mapping (bytes32 => Transaction) m_txs;
+}

solidity_examples/ether_send.sol

@@ -1,31 +0,0 @@
-contract Crowdfunding {
-
-  mapping(address => uint) public balances;
-  address public owner;
-  uint256 INVEST_MIN = 1 ether;
-  uint256 INVEST_MAX = 10 ether;
-
-  modifier onlyOwner() {
-    require(msg.sender == owner);
-    _;
-  }
-
-  function crowdfunding() {
-    owner = msg.sender;
-  }
-
-  function withdrawfunds() onlyOwner {
-    msg.sender.transfer(this.balance);
-  }
-
-  function invest() public payable {
-    require(msg.value > INVEST_MIN && msg.value < INVEST_MAX);
-
-    balances[msg.sender] += msg.value;
-  }
-
-  function getBalance() public constant returns (uint) {
-    return balances[msg.sender];
-  }
-
-}

solidity_examples/etherstore.sol

@@ -0,0 +1,21 @@
+contract EtherStore {
+
+    uint256 public withdrawalLimit = 1 ether;
+    mapping(address => uint256) public lastWithdrawTime;
+    mapping(address => uint256) public balances;
+
+    function depositFunds() public payable {
+        balances[msg.sender] += msg.value;
+    }
+
+    function withdrawFunds (uint256 _weiToWithdraw) public {
+        require(balances[msg.sender] >= _weiToWithdraw);
+        // limit the withdrawal
+        require(_weiToWithdraw <= withdrawalLimit);
+        // limit the time allowed to withdraw
+        require(now >= lastWithdrawTime[msg.sender] + 1 weeks);
+        require(msg.sender.call.value(_weiToWithdraw)());
+        balances[msg.sender] -= _weiToWithdraw;
+        lastWithdrawTime[msg.sender] = now;
+    }
+ }

solidity_examples/hashforether.sol

@@ -0,0 +1,12 @@
+contract HashForEther {
+
+    function withdrawWinnings() {
+        // Winner if the last 8 hex characters of the address are 0. 
+        require(uint32(msg.sender) == 0);
+        _sendWinnings();
+     }
+
+     function _sendWinnings() {
+         msg.sender.transfer(this.balance);
+     }
+}

solidity_examples/timelock.sol

@@ -0,0 +1,21 @@
+contract TimeLock {
+
+    mapping(address => uint) public balances;
+    mapping(address => uint) public lockTime;
+
+    function deposit() public payable {
+        balances[msg.sender] += msg.value;
+        lockTime[msg.sender] = now + 1 weeks;
+    }
+
+    function increaseLockTime(uint _secondsToIncrease) public {
+        lockTime[msg.sender] += _secondsToIncrease;
+    }
+
+    function withdraw() public {
+        require(balances[msg.sender] > 0);
+        require(now > lockTime[msg.sender]);
+        balances[msg.sender] = 0;
+        msg.sender.transfer(balances[msg.sender]);
+    }
+}

solidity_examples/token.sol

@@ -1,4 +1,6 @@
-contract Under {
+pragma solidity ^0.4.18;
+
+contract Token {
 
   mapping(address => uint) balances;
   uint public totalSupply;
@@ -7,7 +9,7 @@ contract Under {
     balances[msg.sender] = totalSupply = _initialSupply;
   }
 
-  function sendeth(address _to, uint _value) public returns (bool) {
+  function transfer(address _to, uint _value) public returns (bool) {
     require(balances[msg.sender] - _value >= 0);
     balances[msg.sender] -= _value;
     balances[_to] += _value;