Adjusting the Position: Part I

Last modified: April 22, 2026

Modifying the Position: Part I

A central component of the minting and liquidity-management logic is the function _modifyPosition. This function is responsible for creating a new position when none exists and for updating an existing one when the owner adds or removes liquidity. In canonical notation, the data required to modify a position are the owner address, the tick interval $[i_a,i_b]$ , and the signed liquidity change $\Delta L$ , which may be positive when liquidity is added or negative when liquidity is removed. Thus, _modifyPosition serves as the main entry point for changing the state of a position.

The core parameter struct and the first part of _modifyPosition are:

struct ModifyPositionParams {
    // the address that owns the position
    address owner;
    // the lower and upper tick of the position
    int24 tickLower;
    int24 tickUpper;
    // any change in liquidity
    int128 liquidityDelta;
}
 
/// @dev Effect some changes to a position
/// @param params the position details and the change to the position's liquidity to effect
/// @return position a storage pointer referencing the position with the given owner and tick range
/// @return amount0 the amount of token0 owed to the pool, negative if the pool should pay the recipient
/// @return amount1 the amount of token1 owed to the pool, negative if the pool should pay the recipient
function _modifyPosition(ModifyPositionParams memory params)
    private
    noDelegateCall
    returns (
        Position.Info storage position,
        int256 amount0,
        int256 amount1
    )
{
    checkTicks(params.tickLower, params.tickUpper);
    Slot0 memory _slot0 = slot0; // SLOAD for gas optimization
 
    position = _updatePosition(
        params.owner,
        params.tickLower,
        params.tickUpper,
        params.liquidityDelta,
        _slot0.tick
    );
 
    // ... remaining _modifyPosition logic
}