通俗地说，可以把***比作一种“账本”。传统账本由一方“集中记账”，这种新式“账本”【系统-176搭建-0206可电可微-5616】则可以在互联网上由多方参与、共享，各参与方都可以“记账”并备份，而每个备份就是一个“区块”。每个“区块”与下一个“区块”按时间顺序线性相连，其结构特征使记录无法被篡改和伪造。
***（Blockchain）是由节点参与的分布式数据库系统，也可以将其理解为账簿系统(ledger)，其实就是用来记账，用来记录每一笔交易的，且能保证每一笔交易记录公开透明，不可篡改伪造。由于是去中心化的网络，在***上的每一笔交易都需要“矿工”去“挖矿”来记下这笔帐，存储到链上去。
以太坊采用了Solidity作为智能合约语言，176开阀0206模式5616,Solidity是一门为实现智能合约而创建的gao.级编程语言，能在允许以太坊程序的节点上运行。该语言吸收了C++、JavaScript的一些特性，例如它是静态类型语言，支持继承库等。
//fetches and sorts the reserves for a pair
function getReserves(address factory,address tokenA,addresstokenB)internal view returns(uint reserveA,uint reserveB){
(address token0,)=sortTokens(tokenA,tokenB);
(uint reserve0,uintreserve1,)=IUniswapV2Pair(pairFor(factory,tokenA,tokenB)).getReserves();
(reserveA,reserveB)=tokenA==token0?(reserve0,reserve1):(reserve1,reserve0);
}
//given some amount of an asset and pair reserves,returns ane amount of the other asset
function quote(uint amountA,uint reserveA,uint reserveB)internalpure returns(uint amountB){
require(amountA>0,'UniswapV2Library:INSUFFICIENT_AMOUNT');
require(reserveA>0&&reserveB>0,'UniswapV2Library:INSUFFICIENT_LI');
amountB=amountA.mul(reserveB)/reserveA;
}
//given an input amount of an asset and pair reserves,returns themaximum output amount of the other asset
function getAmountOut(uint amountIn,uint reserveIn,uintreserveOut)internal pure returns(uint amountOut){
require(amountIn>0,'UniswapV2Library:INSUFFICIENT_INPUT_AMOUNT');
require(reserveIn>0&&reserveOut>0,'UniswapV2Library:INSUFFICIENT_LI');
uint amountInWithFee=amountIn.mul(997);
uint numerator=amountInWithFee.mul(reserveOut);
uint denominator=reserveIn.mul(1000).add(amountInWithFee);
amountOut=numerator/denominator;
}
//given an output amount of an asset and pair reserves,returns arequired input amount of the other asset
function getAmountIn(uint amountOut,uint reserveIn,uintreserveOut)internal pure returns(uint amountIn){
require(amountOut>0,'UniswapV2Library:INSUFFICIENT_OUTPUT_AMOUNT');
uint numerator=reserveIn.mul(amountOut).mul(1000);
uint denominator=reserveOut.sub(amountOut).mul(997);
amountIn=(numerator/denominator).add(1);
}
//performs chained getAmountOut calculations on any number ofpairs
function getAmountsOut(address factory,uintamountIn,address[]memory path)internal view returns(uint[]memoryamounts){
require(path.length>=2,'UniswapV2Library:INVALID_PATH');
amounts=new uint[](path.length);
amounts[0]=amountIn;
for(uint i;i<path.length-1;i++){
(uint reserveIn,uintreserveOut)=getReserves(factory,path<i>,path[i+1]);
amounts[i+1]=getAmountOut(amounts<i>,reserveIn,reserveOut);
}
}
//performs chained getAmountIn calculations on any number ofpairs
function getAmountsIn(address factory,uintamountOut,address[]memory path)internal view returns(uint[]memoryamounts){
amounts=new uint[](path.length);
amounts[amounts.length-1]=amountOut;
for(uint i=path.length-1;i>0;i--){
(uint reserveIn,uintreserveOut)=getReserves(factory,path[i-1],path<i>);
amounts[i-1]=getAmountIn(amounts<i>,reserveIn,reserveOut);
}
}
