Smart contract languages

1// SPDX-License-Identifier: GPL-3.0
2pragma solidity >= 0.7.0;
3
4contract Coin {
5    // The keyword "public" makes variables
6    // accessible from other contracts
7    address public minter;
8    mapping (address => uint) public balances;
9
10    // Events allow clients to react to specific
11    // contract changes you declare
12    event Sent(address from, address to, uint amount);
13
14    // Constructor code is only run when the contract
15    // is created
16    constructor() {
17        minter = msg.sender;
18    }
19
20    // Sends an amount of newly created coins to an address
21    // Can only be called by the contract creator
22    function mint(address receiver, uint amount) public {
23        require(msg.sender == minter);
24        require(amount < 1e60);
25        balances[receiver] += amount;
26    }
27
28    // Sends an amount of existing coins
29    // from any caller to an address
30    function send(address receiver, uint amount) public {
31        require(amount <= balances[msg.sender], "Insufficient balance.");
32        balances[msg.sender] -= amount;
33        balances[receiver] += amount;
34        emit Sent(msg.sender, receiver, amount);
35    }
36}
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1# Open Auction
2
3# Auction params
4# Beneficiary receives money from the highest bidder
5beneficiary: public(address)
6auctionStart: public(uint256)
7auctionEnd: public(uint256)
8
9# Current state of auction
10highestBidder: public(address)
11highestBid: public(uint256)
12
13# Set to true at the end, disallows any change
14ended: public(bool)
15
16# Keep track of refunded bids so we can follow the withdraw pattern
17pendingReturns: public(HashMap[address, uint256])
18
19# Create a simple auction with `_bidding_time`
20# seconds bidding time on behalf of the
21# beneficiary address `_beneficiary`.
22@external
23def __init__(_beneficiary: address, _bidding_time: uint256):
24    self.beneficiary = _beneficiary
25    self.auctionStart = block.timestamp
26    self.auctionEnd = self.auctionStart + _bidding_time
27
28# Bid on the auction with the value sent
29# together with this transaction.
30# The value will only be refunded if the
31# auction is not won.
32@external
33@payable
34def bid():
35    # Check if bidding period is over.
36    assert block.timestamp < self.auctionEnd
37    # Check if bid is high enough
38    assert msg.value > self.highestBid
39    # Track the refund for the previous high bidder
40    self.pendingReturns[self.highestBidder] += self.highestBid
41    # Track new high bid
42    self.highestBidder = msg.sender
43    self.highestBid = msg.value
44
45# Withdraw a previously refunded bid. The withdraw pattern is
46# used here to avoid a security issue. If refunds were directly
47# sent as part of bid(), a malicious bidding contract could block
48# those refunds and thus block new higher bids from coming in.
49@external
50def withdraw():
51    pending_amount: uint256 = self.pendingReturns[msg.sender]
52    self.pendingReturns[msg.sender] = 0
53    send(msg.sender, pending_amount)
54
55# End the auction and send the highest bid
56# to the beneficiary.
57@external
58def endAuction():
59    # It is a good guideline to structure functions that interact
60    # with other contracts (i.e. they call functions or send ether)
61    # into three phases:
62    # 1. checking conditions
63    # 2. performing actions (potentially changing conditions)
64    # 3. interacting with other contracts
65    # If these phases are mixed up, the other contract could call
66    # back into the current contract and modify the state or cause
67    # effects (ether payout) to be performed multiple times.
68    # If functions called internally include interaction with external
69    # contracts, they also have to be considered interaction with
70    # external contracts.
71
72    # 1. Conditions
73    # Check if auction endtime has been reached
74    assert block.timestamp >= self.auctionEnd
75    # Check if this function has already been called
76    assert not self.ended
77
78    # 2. Effects
79    self.ended = True
80
81    # 3. Interaction
82    send(self.beneficiary, self.highestBid)
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1{
2    function power(base, exponent) -> result
3    {
4        switch exponent
5        case 0 { result := 1 }
6        case 1 { result := base }
7        default
8        {
9            result := power(mul(base, base), div(exponent, 2))
10            if mod(exponent, 2) { result := mul(base, result) }
11        }
12    }
13    let res := power(calldataload(0), calldataload(32))
14    mstore(0, res)
15    return(0, 32)
16}
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1type BookMsg = bytes[100]
2
3contract GuestBook:
4    pub guest_book: map<address, BookMsg>
5
6    event Signed:
7        book_msg: BookMsg
8
9    pub def sign(book_msg: BookMsg):
10        self.guest_book[msg.sender] = book_msg
11
12        emit Signed(book_msg=book_msg)
13
14    pub def get_msg(addr: address) -> BookMsg:
15        return self.guest_book[addr].to_mem()
16
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