StandardToken first version

contracts/StandardToken.sol

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+pragma solidity ^0.4.0;
+
+import './ERC20.sol';
+import './SafeMath.sol';
+
+/**
+ * ERC20 token
+ *
+ * https://github.com/ethereum/EIPs/issues/20
+ * Based on code by FirstBlood:
+ * https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
+ */
+contract StandardToken is ERC20, SafeMath {
+
+  mapping(address => uint256) balances;
+  mapping (address => mapping (address => uint256)) allowed;
+  uint256 public totalSupply;
+
+  function transfer(address _to, uint256 _value) returns (bool success) {
+    if (balances[msg.sender] < _value) {
+      throw;
+    } 
+    balances[msg.sender] = safeSub(balances[msg.sender], _value);
+    balances[_to] = safeAdd(balances[_to], _value);
+    Transfer(msg.sender, _to, _value);
+    return true;
+  }
+
+  function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
+    var _allowance = allowed[_from][msg.sender];
+    if (balances[_from] < _value ||
+        _allowance < _value)) {
+      throw;
+    }
+
+    balances[_to] = safeAdd(balances[_to], _value);
+    balances[_from] = safeSub(balances[_from], _value);
+    allowed[_from][msg.sender] = safeSub(_allowance, _value);
+    Transfer(_from, _to, _value);
+    return true;
+  }
+
+  function balanceOf(address _owner) constant returns (uint256 balance) {
+    return balances[_owner];
+  }
+
+  function approve(address _spender, uint256 _value) returns (bool success) {
+    allowed[msg.sender][_spender] = _value;
+    Approval(msg.sender, _spender, _value);
+    return true;
+  }
+
+  function allowance(address _owner, address _spender) constant returns (uint256 remaining) {
+    return allowed[_owner][_spender];
+  }
+
+}