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　　tokenToEthInput通過(guò)token.balanceOf獲得代幣兌換合約當(dāng)前的代幣ERC20代幣存儲(chǔ)量，然后用getInputPrice獲得可兌換到的ETH的數(shù)量，接著用as_wei_value將單位轉(zhuǎn)換成wei后用send函數(shù)將eth發(fā)送給接收者，最后再調(diào)用transferForm從buyer手中收取應(yīng)當(dāng)支付的代幣。

　　#dev Pricing function for converting between ETH and Tokens.

　　#param input_amount Amount of ETH or Tokens being sold.

　　#param input_reserve Amount of ETH or Tokens(input type)in exchange reserves.

　　#param output_reserve Amount of ETH or Tokens(output type)in exchange reserves.

　　#return Amount of ETH or Tokens bought.關(guān)于區(qū)塊鏈項(xiàng)目技術(shù)開(kāi)發(fā)唯:MrsFu123，代幣發(fā)行、dapp智能合約開(kāi)發(fā)、鏈游開(kāi)發(fā)、多鏈錢(qián)包開(kāi)發(fā)

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　　private

　　constant

　　def getInputPrice(input_amount:uint256,input_reserve:uint256,output_reserve:uint256)->uint256:案例及設(shè)計(jì)I35詳細(xì)7O98開(kāi)發(fā)O7I8

　　assert input_reserve>0 and output_reserve>0#需要兩幣的儲(chǔ)備都大于0

　　input_amount_with_fee:uint256=input_amount*997#抽取千分之3手續(xù)費(fèi)

　　numerator:uint256=input_amount_with_fee*output_reserve

　　denominator:uint256=(input_reserve*1000)+input_amount_with_fee

　　return numerator/denominator

　　private

　　def tokenToEthOutput(eth_bought:uint256(wei),max_tokens:uint256,deadline:timestamp,buyer:address,recipient:address)->uint256:

　　assert deadline>=block.timestamp and eth_bought>0

　　token_reserve:uint256=self.token.balanceOf(self)#獲取代幣儲(chǔ)備量

　　#通過(guò)getOutputPrice計(jì)算所需要花費(fèi)的代幣數(shù)量

　　tokens_sold:uint256=self.getOutputPrice(as_unitless_number(eth_bought),token_reserve,as_unitless_number(self.balance))

　　#tokens sold is always>0

　　assert max_tokens>=tokens_sold

　　send(recipient,eth_bought)#向接收者發(fā)送所兌換得到的ETH

　　assert self.token.transferFrom(buyer,self,tokens_sold)#從購(gòu)買(mǎi)者收取代幣

　　log.EthPurchase(buyer,tokens_sold,eth_bought)

　　return tokens_sold