Swap Direction

Understanding X→Y vs Y→X swaps in DLMM. Token ordering determines swap direction and affects how you interact with pairs.

Token Ordering in DLMM

In every pair:

• Token X: The token with the smaller address (sorted)

• Token Y: The token with the larger address

• This ordering is permanent and automatic

// Example ordering
TokenX: "0x2::sui::SUI"        // Smaller address
TokenY: "0xabc...::usdc::USDC" // Larger address

// SUI is always X, USDC is always Y in this pair

Understanding Swap Directions

X→Y Swap (xtoy = true)

• Selling Token X

• Buying Token Y

• Price moves UP (more Y per X)

Y→X Swap (xtoy = false)

• Selling Token Y

• Buying Token X

• Price moves DOWN (less Y per X)

Checking Token Order

const pair = await sdk.Pair.getPair(pairAddress);

console.log("Token X:", pair.tokenXType);
console.log("Token Y:", pair.tokenYType);

// Determine what xtoy means for this pair
if (pair.tokenXType.includes("SUI")) {
  console.log("xtoy=true: Sell SUI for USDC");
  console.log("xtoy=false: Sell USDC for SUI");
}

Common Patterns

Swap by Token Type

async function swapTokens(
  pair: LBPair,
  inputToken: string,
  amount: bigint
) {
  // Determine direction based on input token
  const xtoy = inputToken === pair.tokenXType;
  
  return await sdk.Swap.prepareSwap(pair, {
    amount,
    xtoy
  });
}

User-Friendly Wrapper

// Helper for intuitive swapping
async function swap(
  pair: LBPair,
  fromToken: string,
  toToken: string,
  amount: bigint
) {
  // Validate tokens belong to pair
  const hasTokens = 
    (fromToken === pair.tokenXType || fromToken === pair.tokenYType) &&
    (toToken === pair.tokenXType || toToken === pair.tokenYType);
    
  if (!hasTokens) {
    throw new Error("Invalid token pair");
  }
  
  // Set direction
  const xtoy = fromToken === pair.tokenXType;
  
  return await sdk.Swap.prepareSwap(pair, {
    amount,
    xtoy
  });
}

Price Movement

// How swaps affect price
if (xtoy) {
  // Selling X for Y
  // Depletes Y reserves in bins
  // Price moves to higher bins
  // X becomes cheaper relative to Y
} else {
  // Selling Y for X
  // Depletes X reserves in bins
  // Price moves to lower bins
  // X becomes more expensive relative to Y
}

Quick Reference

Want to	Token In	Token Out	Use
Buy SUI	USDC (Y)	SUI (X)	xtoy: false
Sell SUI	SUI (X)	USDC (Y)	xtoy: true
Buy USDC	SUI (X)	USDC (Y)	xtoy: true
Sell USDC	USDC (Y)	SUI (X)	xtoy: false

Common Mistakes

// ❌ Wrong: Assuming token order
const tx = await sdk.Swap.prepareSwap(pair, {
  amount,
  xtoy: true // Assumes first token is X
});

// ✅ Correct: Check actual order
const sellingTokenX = inputToken === pair.tokenXType;
const tx = await sdk.Swap.prepareSwap(pair, {
  amount,
  xtoy: sellingTokenX
});

Related Topics

• Execute Swap - Perform swaps

• Get Single Pair - Check token order

• Calculate Swap Output - Preview results