Blockchain Smart Contracts with Solidity · 课时

AMM 与流动性池

了解 Uniswap 等自动化做市商（AMM）的工作方式，以及流动性池如何支持去中心化交易。

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AMM 与流动性池 是 CoddyKit 上的免费 Blockchain Smart Contracts with Solidity 课时。这是第 1 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 Blockchain Smart Contracts with Solidity 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Blockchain Smart Contracts with Solidity 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Welcome to AMMs

Decentralized Finance (DeFi) has revolutionized how we trade assets. At its heart are Automated Market Makers (AMMs).

AMMs power decentralized exchanges (DEXs) like Uniswap, allowing users to swap tokens without traditional buyers and sellers.

Instead of matching orders, AMMs use mathematical formulas and liquidity pools.

Order Books vs. AMMs

Traditional exchanges use order books, where buyers and sellers list their desired prices. Trades only happen when bids and asks match.

Order Books: Centralized, requires matching orders, can suffer from low liquidity.
AMMs: Decentralized, uses liquidity pools, always offers a price determined by a formula.

AMMs solve the liquidity problem for many token pairs on a blockchain by always providing a market.

The Power of Liquidity Pools

An AMM's backbone is the liquidity pool. This is a collection of two or more tokens locked in a smart contract.

For example, a common pool might hold ETH and a stablecoin like DAI. Users can swap between these tokens directly from the pool.

These pools are funded by individuals called Liquidity Providers (LPs).

Meet the Constant Product Formula

Most AMMs, like Uniswap, use the constant product formula: x * y = k.

x is the quantity of the first token.
y is the quantity of the second token.
k is a constant product that must remain unchanged after a trade.

When you swap tokens, the quantities of x and y change, but their product k stays the same, determining the new price ratio.

How to Become an LP

Liquidity Providers (LPs) deposit an equal value of two tokens into a liquidity pool. For example, $1000 worth of ETH and $1000 worth of DAI.

In return, LPs receive Liquidity Pool (LP) tokens. These tokens represent their share of the pool.

LP tokens can be redeemed later to withdraw your original deposit plus any accumulated fees.

Adding Liquidity in Practice

When an LP adds liquidity, they increase the total supply of x and y in the pool, which also increases the constant k.

The AMM smart contract ensures that tokens are added in the correct ratio to maintain the pool's balance and prevent immediate price changes.

This process makes the pool deeper, allowing for larger trades with less price impact.

Swapping Tokens

When a user wants to swap Token A for Token B, they send Token A to the liquidity pool.

The AMM's smart contract then calculates how much Token B to give back, based on the x * y = k formula.

The pool's balance shifts, and the price of the tokens adjusts automatically according to the formula.

Code Example: Simulating a Swap

Let's see a simplified Solidity contract that simulates how an AMM might perform a swap using the constant product formula.

This example demonstrates the core calculation and reserve update.

pragma solidity ^0.8.0;

contract SimpleAmmSwap {
    uint public tokenXReserve = 1000 * 10**18; // 1000 tokens (e.g., ETH) with 18 decimals
    uint public tokenYReserve = 1000 * 10**18; // 1000 tokens (e.g., DAI) with 18 decimals
    uint public k = tokenXReserve * tokenYReserve;

    // Simulate a swap from Token X to Token Y
    // For simplicity, no actual token transfers, just reserve updates.
    function swapXForY(uint amountInX) public returns (uint amountOutY) {
        require(amountInX > 0, "Amount in must be positive");
        
        // Calculate new reserves and output amount
        uint newXReserve = tokenXReserve + amountInX;
        uint newYReserve = k / newXReserve;
        amountOutY = tokenYReserve - newYReserve;

        require(amountOutY > 0, "Not enough liquidity for swap");

        // Update reserves
        tokenXReserve = newXReserve;
        tokenYReserve = newYReserve;

        // Note: In a real AMM, actual token transfers would occur here.
    }

    // A getter to check current reserves
    function getReserves() public view returns (uint, uint) {
        return (tokenXReserve, tokenYReserve);
    }
}

Understanding Impermanent Loss

One major risk for LPs is impermanent loss. This occurs when the price of the assets in the liquidity pool changes relative to when you deposited them.

If the price ratio diverges significantly, the value of your tokens withdrawn from the pool might be less than if you had simply held them outside the pool.

It's called "impermanent" because the loss only becomes permanent if you withdraw your liquidity before the prices return to their original ratio.

LP Fees and Rewards

Despite impermanent loss, LPs are incentivized by earning a share of the trading fees generated by the pool.

Each time a trade occurs, a small percentage (e.g., 0.3%) of the swapped amount is added to the liquidity pool.

These fees accumulate in the pool and are distributed proportionally to LPs when they withdraw their liquidity, compensating them for providing capital and taking on impermanent loss risk.

Quick Check: AMM Basics

Test your understanding of Automated Market Makers and Liquidity Pools.

在交互式课程中回答

Recap: AMMs & Liquidity Pools

We've explored how Automated Market Makers (AMMs) provide decentralized trading by using liquidity pools instead of traditional order books.

Key takeaways:

AMMs use formulas like x * y = k to determine prices.
Liquidity Providers (LPs) fund pools and earn trading fees.
Impermanent loss is a risk for LPs due to price divergence.

Understanding these concepts is vital for navigating the DeFi landscape!

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常见问题解答

「AMM 与流动性池」课时是免费的吗？

是的 — 「AMM 与流动性池」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Blockchain Smart Contracts with Solidity 课程的其余内容，请升级到 CoddyKit PRO。 Blockchain Smart Contracts with Solidity 课程共包含 4 节课。

「AMM 与流动性池」这节课中我会学到什么？

了解 Uniswap 等自动化做市商（AMM）的工作方式，以及流动性池如何支持去中心化交易。你通过在浏览器中直接运行的动手代码来练习 Blockchain Smart Contracts with Solidity，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Blockchain Smart Contracts with Solidity 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Blockchain Smart Contracts with Solidity 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 1 节课，共 4 节。

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大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

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