# Single Swaps

For a token to token swap through a single pool the following Balancer Router functions should be used: swapSingleTokenExactIn and swapSingleTokenExactOut are the most gas efficient functions to use.

Checkout Javascript and Solidity examples here.

# Multi-path Swaps

Swaps paths constructed of steps through multiple pools/tokens the following Batch Router functions should be used: swapExactIn and swapExactOut functions.

A SwapPathStep is defined as:

struct SwapPathStep {
    address pool;
    IERC20 tokenOut;
    // If true, the "pool" is an ERC4626 Buffer. Used to wrap/unwrap tokens if pool doesn't have enough liquidity.
    bool isBuffer;
}

and paths can include add/remove liquidity steps by using the address of the respective pool. For example, the following SwapPathExactAmountIn would execute a swap of USDC to BAL then add liquidity to the 80/20 BAL/WETH pool.

// Note - pseudo code
SwapPathExactAmountIn {
    tokenIn: USDC
    // for each step:
    // if tokenIn == pool use removeLiquidity SINGLE_TOKEN_EXACT_IN
    // if tokenOut == pool use addLiquidity UNBALANCED
    steps: [
        { 
            pool: '0xBAL_USDC_POOL',
            tokenOut: '0xBAL',
            isBuffer: false
        },
        {
            pool: '0xB-80BAL-20WETH_POOL',
            tokenOut: '0xB-80BAL-20WETH_POOL',
            isBuffer: false
        }
    ]
    exactAmountIn: 1000000,
    minAmountOut: 100000
}

Checkout Javascript and Solidity examples here.

# Simulating Swaps Using Query Functions

Queries provide the ability to simulate an operation and find its result without executing a transaction. Balancer Routers provide a query for all state changing liquidity operations including single and multi-path swap functions, e.g. querySwapSingleTokenExactIn.