Go/
  bin/
  pkg/
  src/

package main //namespace declaration 하는 부분으로 기능과 논리들을 그룹화시켜준다.

import "fmt" // format의 약자로 standard lib에 있다.

// 여기서 main 은 keyword 로써 해당 함수가 라이브러리가 아닌 어플리케이션으로 동작함을 나타낸다.
// go 어플리케이션이 여기서 시작된다.
// func는 function을 선언하는 keyword 이다.
func main() {
  fmt.Println("Hello, World") //여기서 println의 앞의 P가 대문자 인데, 이는 외부 라이브러리에서 가져왔음을 의미한다.
                              // 같은 원리로 함수를 선언할때 대문자로 시작하면 외부에서 접근이 가능한 것이다.
}

go run main.go

go build # 실행가능한 binary 파일을 만들어 준다.
이 경우 파일명이 아니라 폴더 명으로 파일이 생성된다.
./go-study

윈도우용 빌드
GOOS=windows go build -o main.exe main.go

package main

import "fmt"

func main() {
    p := []int{2, 3, 5, 7, 11, 13}
    fmt.Println("p ==", p)

    for i := 0; i < len(p); i++ {
        fmt.Printf("p[%d] == %d\n",
            i, p[i])
    }
}

package main

import "fmt"

var pow = []int{1, 2, 4, 8, 16, 32, 64, 128}

func main() {
    for i, v := range pow {
        fmt.Printf("2**%d = %d\n", i, v)
    }
}

package main

import "fmt"

func main() {
    pow := make([]int, 10)
    for i := range pow {
        pow[i] = 1 << uint(i)
    }
    for _, value := range pow {
        fmt.Printf("%d\n", value)
    }
}

package main

import "fmt"

type Vertex struct {
    Lat, Long float64
}

var m map[string]Vertex

func main() {
    m = make(map[string]Vertex)
    m["Bell Labs"] = Vertex{
        40.68433, -74.39967,
    }
    fmt.Println(m["Bell Labs"])
}

package main

import "fmt"

type Vertex struct {
    Lat, Long float64
}

var m = map[string]Vertex{
    "Bell Labs": Vertex{
        40.68433, -74.39967,
    },
    "Google": Vertex{
        37.42202, -122.08408,
    },
}

func main() {
    fmt.Println(m)
}

package main

import "fmt"

func main() {
    m := make(map[string]int)

    m["Answer"] = 42
    fmt.Println("The value:", m["Answer"])

    m["Answer"] = 48
    fmt.Println("The value:", m["Answer"])

    delete(m, "Answer")
    fmt.Println("The value:", m["Answer"])

    v, ok := m["Answer"]
    fmt.Println("The value:", v, "Present?", ok)
}

package main

import (
    "fmt"
    "runtime"
)

func main() {
    fmt.Print("Go runs on ")
    switch os := runtime.GOOS; os {
    case "darwin":
        fmt.Println("OS X.")
    case "linux":
        fmt.Println("Linux.")
    default:
        // freebsd, openbsd,
        // plan9, windows...
        fmt.Printf("%s.", os)
    }
}

package main

import (
    "fmt"
    "math"
)

type Vertex struct {
    X, Y float64
}

func (v *Vertex) Abs() float64 {
    return math.Sqrt(v.X*v.X + v.Y*v.Y)
}

func main() {
    v := &Vertex{3, 4}
    fmt.Println(v.Abs())
}

package main

import (
    "fmt"
    "math"
)

type Abser interface {
    Abs() float64
}

func main() {
    var a Abser
    f := MyFloat(-math.Sqrt2)
    v := Vertex{3, 4}

    a = f  // a MyFloat implements Abser
    a = &v // a *Vertex implements Abser
    a = v  // a Vertex, does NOT
    // implement Abser

    fmt.Println(a.Abs())
}

type MyFloat float64

func (f MyFloat) Abs() float64 {
    if f < 0 {
        return float64(-f)
    }
    return float64(f)
}

type Vertex struct {
    X, Y float64
}

func (v *Vertex) Abs() float64 {
    return math.Sqrt(v.X*v.X + v.Y*v.Y)

pragma solidity ^0.4.20;

contract MyToken {
    event Transfer(address indexed from, address indexed to, uint256 value);
    /* This creates an array with all balances */
    mapping (address => uint256) public balanceOf;
    string public name;
    string public symbol;
    uint8 public decimals;
    /* Initializes contract with initial supply tokens to the creator of the contract */
    function MyToken(uint256 initialSupply, string tokenName, string tokenSymbol, uint8 decimalUnits) public {
        balanceOf[msg.sender] = initialSupply;              // Give the creator all initial tokens
        name = tokenName;                                   // Set the name for display purposes
        symbol = tokenSymbol;                               // Set the symbol for display purposes
        decimals = decimalUnits;                            // Amount of decimals for display purposes
    }

    /* Send coins */
    function transfer(address _to, uint256 _value) public {
        require(balanceOf[msg.sender] >= _value);           // Check if the sender has enough
        require(balanceOf[_to] + _value >= balanceOf[_to]); // Check for overflows
        balanceOf[msg.sender] -= _value;                    // Subtract from the sender
        balanceOf[_to] += _value;                           // Add the same to the recipient
        /* Notify anyone listening that this transfer took place */
        emit Transfer(msg.sender, _to, _value);
    }
}

pragma solidity ^0.4.16;

interface token {
    function transfer(address receiver, uint amount) external;
}

contract Crowdsale {
    address public beneficiary;
    uint public fundingGoal;
    uint public amountRaised;
    uint public deadline; //마감 기한
    uint public price;
    token public tokenReward;
    mapping(address => uint256) public balanceOf;
    bool fundingGoalReached = false;
    bool crowdsaleClosed = false;

    event GoalReached(address recipient, uint totalAmountRaised);
    event FundTransfer(address backer, uint amount, bool isContribution);

    /**
     * Constructor function
     *
     * Setup the owner
     */
    function Crowdsale(
        address ifSuccessfulSendTo, //
        uint fundingGoalInEthers, //이더 단위의 모금 목표액
        uint durationInMinutes, //분 단위의 모금 기간
        uint etherCostOfEachToken, //각 토큰 당 단위 가격(이더 기준)
        address addressOfTokenUsedAsReward //모금의 보상으로 주어질 위에서 만든 토큰의 주소
    ) public {
        beneficiary = ifSuccessfulSendTo;
        fundingGoal = fundingGoalInEthers * 1 ether;
        deadline = now + durationInMinutes * 1 minutes;
        price = etherCostOfEachToken * 1 ether;
        tokenReward = token(addressOfTokenUsedAsReward);
    }

    /**
     * Fallback function
     *
     * The function without name is the default function that is called whenever anyone sends funds to a contract
     */
    function () payable public {
        require(!crowdsaleClosed);
        uint amount = msg.value;
        balanceOf[msg.sender] += amount;
        amountRaised += amount;
        tokenReward.transfer(msg.sender, amount / price);
        emit FundTransfer(msg.sender, amount, true);
    }

    modifier afterDeadline() { if (now >= deadline) _; }

    /**
     * Check if goal was reached
     *
     * Checks if the goal or time limit has been reached and ends the campaign
     */
    function checkGoalReached() afterDeadline public {
        if (amountRaised >= fundingGoal){
            fundingGoalReached = true;
            emit GoalReached(beneficiary, amountRaised);
        }
        crowdsaleClosed = true;
    }


    /**
     * Withdraw the funds
     *
     * Checks to see if goal or time limit has been reached, and if so, and the funding goal was reached,
     * sends the entire amount to the beneficiary. If goal was not reached, each contributor can withdraw
     * the amount they contributed.
     */
    function safeWithdrawal() afterDeadline public {
        if (!fundingGoalReached) {
            uint amount = balanceOf[msg.sender];
            balanceOf[msg.sender] = 0;
            if (amount > 0) {
                if (msg.sender.send(amount)) {
                    emit FundTransfer(msg.sender, amount, false);
                } else {
                    balanceOf[msg.sender] = amount;
                }
            }
        }

        if (fundingGoalReached && beneficiary == msg.sender) {
            if (beneficiary.send(amountRaised)) {
                emit FundTransfer(beneficiary, amountRaised, false);
            } else {
                //If we fail to send the funds to beneficiary, unlock funders balance
                fundingGoalReached = false;
            }
        }
    }
}

pragma solidity ^0.4.20;

contract MyToken {
    event Transfer(address indexed from, address indexed to, uint256 value);
    /* This creates an array with all balances */
    mapping (address => uint256) public balanceOf;
    string public name;
    string public symbol;
    uint8 public decimals;
    /* Initializes contract with initial supply tokens to the creator of the contract */
    function MyToken(uint256 initialSupply, string tokenName, string tokenSymbol, uint8 decimalUnits) public {
        balanceOf[msg.sender] = initialSupply;              // Give the creator all initial tokens
        name = tokenName;                                   // Set the name for display purposes
        symbol = tokenSymbol;                               // Set the symbol for display purposes
        decimals = decimalUnits;                            // Amount of decimals for display purposes
    }

    /* Send coins */
    function transfer(address _to, uint256 _value) public {
        require(balanceOf[msg.sender] >= _value);           // Check if the sender has enough
        require(balanceOf[_to] + _value >= balanceOf[_to]); // Check for overflows
        balanceOf[msg.sender] -= _value;                    // Subtract from the sender
        balanceOf[_to] += _value;                           // Add the same to the recipient
        /* Notify anyone listening that this transfer took place */
        emit Transfer(msg.sender, _to, _value);
    }
}

pragma solidity ^0.4.20;

contract owned {
    address public owner;

    function owned() {
        owner = msg.sender;
    }

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    function transferOwnership(address newOwner) onlyOwner {
        owner = newOwner;
    }
}

contract MyToken is owned{
    event Transfer(address indexed from, address indexed to, uint256 value);
    /* This creates an array with all balances */
    mapping (address => uint256) public balanceOf;
    string public name;
    string public symbol;
    uint8 public decimals;
    /* Initializes contract with initial supply tokens to the creator of the contract */
    function MyToken(
        uint256 initialSupply,
        string tokenName,
        uint8 decimalUnits,
        string tokenSymbol,
        address centralMinter
        ) {
        if(centralMinter != 0 ) owner = centralMinter;
    }

    /* Send coins */
    function transfer(address _to, uint256 _value) public {
        require(balanceOf[msg.sender] >= _value);           // Check if the sender has enough
        require(balanceOf[_to] + _value >= balanceOf[_to]); // Check for overflows
        balanceOf[msg.sender] -= _value;                    // Subtract from the sender
        balanceOf[_to] += _value;                           // Add the same to the recipient
        /* Notify anyone listening that this transfer took place */
        emit Transfer(msg.sender, _to, _value);
    }
}

pragma solidity ^0.4.16;

contract owned {
    address public owner;

    function owned() public {
        owner = msg.sender;
    }

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    function transferOwnership(address newOwner) onlyOwner public {
        owner = newOwner;
    }
}

interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external; }

contract TokenERC20 {
    // Public variables of the token
    string public name;
    string public symbol;
    uint8 public decimals = 18;
    // 18 decimals is the strongly suggested default, avoid changing it
    uint256 public totalSupply;

    // This creates an array with all balances
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);

    // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);

    /**
     * Constrctor function
     *
     * Initializes contract with initial supply tokens to the creator of the contract
     */
    function TokenERC20(
        uint256 initialSupply,
        string tokenName,
        string tokenSymbol
    ) public {
        totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
        balanceOf[msg.sender] = totalSupply;                // Give the creator all initial tokens
        name = tokenName;                                   // Set the name for display purposes
        symbol = tokenSymbol;                               // Set the symbol for display purposes
    }

    /**
     * Internal transfer, only can be called by this contract
     */
    function _transfer(address _from, address _to, uint _value) internal {
        // Prevent transfer to 0x0 address. Use burn() instead
        require(_to != 0x0);
        // Check if the sender has enough
        require(balanceOf[_from] >= _value);
        // Check for overflows
        require(balanceOf[_to] + _value > balanceOf[_to]);
        // Save this for an assertion in the future
        uint previousBalances = balanceOf[_from] + balanceOf[_to];
        // Subtract from the sender
        balanceOf[_from] -= _value;
        // Add the same to the recipient
        balanceOf[_to] += _value;
        emit Transfer(_from, _to, _value);
        // Asserts are used to use static analysis to find bugs in your code. They should never fail
        assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
    }

    /**
     * Transfer tokens
     *
     * Send `_value` tokens to `_to` from your account
     *
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transfer(address _to, uint256 _value) public {
        _transfer(msg.sender, _to, _value);
    }

    /**
     * Transfer tokens from other address
     *
     * Send `_value` tokens to `_to` in behalf of `_from`
     *
     * @param _from The address of the sender
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_value <= allowance[_from][msg.sender]);     // Check allowance
        allowance[_from][msg.sender] -= _value;
        _transfer(_from, _to, _value);
        return true;
    }

    /**
     * Set allowance for other address
     *
     * Allows `_spender` to spend no more than `_value` tokens in your behalf
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     */
    function approve(address _spender, uint256 _value) public
        returns (bool success) {
        allowance[msg.sender][_spender] = _value;
        return true;
    }

    /**
     * Set allowance for other address and notify
     *
     * Allows `_spender` to spend no more than `_value` tokens in your behalf, and then ping the contract about it
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     * @param _extraData some extra information to send to the approved contract
     */
    function approveAndCall(address _spender, uint256 _value, bytes _extraData)
        public
        returns (bool success) {
        tokenRecipient spender = tokenRecipient(_spender);
        if (approve(_spender, _value)) {
            spender.receiveApproval(msg.sender, _value, this, _extraData);
            return true;
        }
    }

    /**
     * Destroy tokens
     *
     * Remove `_value` tokens from the system irreversibly
     *
     * @param _value the amount of money to burn
     */
    function burn(uint256 _value) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
        balanceOf[msg.sender] -= _value;            // Subtract from the sender
        totalSupply -= _value;                      // Updates totalSupply
        emit Burn(msg.sender, _value);
        return true;
    }

    /**
     * Destroy tokens from other account
     *
     * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
     *
     * @param _from the address of the sender
     * @param _value the amount of money to burn
     */
    function burnFrom(address _from, uint256 _value) public returns (bool success) {
        require(balanceOf[_from] >= _value);                // Check if the targeted balance is enough
        require(_value <= allowance[_from][msg.sender]);    // Check allowance
        balanceOf[_from] -= _value;                         // Subtract from the targeted balance
        allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
        totalSupply -= _value;                              // Update totalSupply
        emit Burn(_from, _value);
        return true;
    }
}

/******************************************/
/*       ADVANCED TOKEN STARTS HERE       */
/******************************************/

contract MyAdvancedToken is owned, TokenERC20 {

    uint256 public sellPrice;
    uint256 public buyPrice;

    mapping (address => bool) public frozenAccount;

    /* This generates a public event on the blockchain that will notify clients */
    event FrozenFunds(address target, bool frozen);

    /* Initializes contract with initial supply tokens to the creator of the contract */
    function MyAdvancedToken(
        uint256 initialSupply,
        string tokenName,
        string tokenSymbol
    ) TokenERC20(initialSupply, tokenName, tokenSymbol) public {}

    /* Internal transfer, only can be called by this contract */
    function _transfer(address _from, address _to, uint _value) internal {
        require (_to != 0x0);                               // Prevent transfer to 0x0 address. Use burn() instead
        require (balanceOf[_from] >= _value);               // Check if the sender has enough
        require (balanceOf[_to] + _value >= balanceOf[_to]); // Check for overflows
        require(!frozenAccount[_from]);                     // Check if sender is frozen
        require(!frozenAccount[_to]);                       // Check if recipient is frozen
        balanceOf[_from] -= _value;                         // Subtract from the sender
        balanceOf[_to] += _value;                           // Add the same to the recipient
        emit Transfer(_from, _to, _value);
    }

    /// @notice Create `mintedAmount` tokens and send it to `target`
    /// @param target Address to receive the tokens
    /// @param mintedAmount the amount of tokens it will receive
    function mintToken(address target, uint256 mintedAmount) onlyOwner public {
        balanceOf[target] += mintedAmount;
        totalSupply += mintedAmount;
        emit Transfer(0, this, mintedAmount);
        emit Transfer(this, target, mintedAmount);
    }

    /// @notice `freeze? Prevent | Allow` `target` from sending & receiving tokens
    /// @param target Address to be frozen
    /// @param freeze either to freeze it or not
    function freezeAccount(address target, bool freeze) onlyOwner public {
        frozenAccount[target] = freeze;
        emit FrozenFunds(target, freeze);
    }

    /// @notice Allow users to buy tokens for `newBuyPrice` eth and sell tokens for `newSellPrice` eth
    /// @param newSellPrice Price the users can sell to the contract
    /// @param newBuyPrice Price users can buy from the contract
    function setPrices(uint256 newSellPrice, uint256 newBuyPrice) onlyOwner public {
        sellPrice = newSellPrice;
        buyPrice = newBuyPrice;
    }

    /// @notice Buy tokens from contract by sending ether
    function buy() payable public {
        uint amount = msg.value / buyPrice;               // calculates the amount
        _transfer(this, msg.sender, amount);              // makes the transfers
    }

    /// @notice Sell `amount` tokens to contract
    /// @param amount amount of tokens to be sold
    function sell(uint256 amount) public {
        require(address(this).balance >= amount * sellPrice);      // checks if the contract has enough ether to buy
        _transfer(msg.sender, this, amount);              // makes the transfers
        msg.sender.transfer(amount * sellPrice);          // sends ether to the seller. It's important to do this last to avoid recursion attacks
    }
}

npm install -g solc

solcjs -o target --bin --abi Greeter.sol

var greeterFactory = eth.contract(<contents of the file Greeter.abi>)

var greeterCompiled = "0x" + "<contents of the file Greeter.bin>"

var _greeting = "Hello World!"

var greeter = greeterFactory.new(_greeting,{from:eth.accounts[0],data:greeterCompiled,gas:47000000}, function(e, contract){
    if(e) {
      console.error(e); // If something goes wrong, at least we'll know.
      return;
    }

    if(!contract.address) {
      console.log("Contract transaction send: TransactionHash: " + contract.transactionHash + " waiting to be mined...");

    } else {
      console.log("Contract mined! Address: " + contract.address);
      console.log(contract);
    }
})

loadScript("main.js")

miner.start()

greeter.greet();