Curve StableSwap Exchange: LP Tokens

In exchange for depositing coins into a Curve pool (see Curve Pools), liquidity providers receive pool LP tokens. A Curve pool LP token is an ERC20 contract specific to the Curve pool. Hence, LP tokens are transferrable. Holders of pool LP tokens may stake the token into a pool’s liquidity gauge in order to receive CRV token rewards. Alternatively, if the LP token is supported by a metapool, the token may be deposited into the respective metapool in exchange for the metapool’s LP token (see here).

The following versions of Curve pool LP tokens exist:

The version of each pool’s LP token can be found in the Deployment Addresses.

Note

For older Curve pools the token attribute is not always public and a getter has not been explicitly implemented.

Curve Token V1

The implementation for a Curve Token V1 may be viewed on GitHub.

CurveToken.name() → string[64]: view

Get the name of the token.

>>> lp_token.name()
'Curve.fi yDAI/yUSDC/yUSDT/yBUSD'
CurveToken.symbol() → string[32]: view

Get the token symbol.

>>> lp_token.symbol()
'yDAI+yUSDC+yUSDT+yBUSD'
CurveToken.decimals() → uint256: view

Get the number of decimals for the token.

>>> lp_token.decimals()
18
CurveToken.balanceOf(account: address) → uint256: view

Get the token balance for an account.

  • account: Address to get the token balance for

>>> lp_token.balanceOf("0x69fb7c45726cfe2badee8317005d3f94be838840")
72372801850459006740117197
CurveToken.totalSupply() → uint256: view

Get the total token supply.

>>> lp_token.totalSupply()
73112516629065063732935484
CurveToken.allowance(_owner: address, _spender: address) → uint256: view

Get the allowance of an account to spend on behalf of some other account.

  • _owner: Account that is paying when _spender spends the allowance

  • _spender: Account that can spend up to the allowance

Returns the allowance of _spender for _owner.

CurveToken.transfer(_to: address, _value: uint256)bool

Transfer tokens to a specified address.

  • _to: Receiver of the tokens

  • _value: Amount of tokens to transfer

Returns True if the transfer succeeded.

CurveToken.transferFrom(_from: address, _to: address, _value: uint256)bool

Transfer tokens from one address to another. Note that while this function emits a Transfer event, this is not required as per the specification, and other compliant implementations may not emit the event.

  • _from: Address which you want to send tokens from

  • _to: Address which you want to transfer to

  • _value: Amount of tokens to be transferred

Returns True if transfer succeeded.

CurveToken.approve(_spender: address, _value: uint256)bool

Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.

Beware that changing an allowance with this method brings the risk that someone may use both the old and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this race condition is to first reduce the spender’s allowance to 0 and set the desired value afterwards (see this GitHub issue).

  • _spender: Address which will spend the funds.

  • _value: Amount of tokens to be spent.

Returns True if approval succeeded.

Warning

For Curve LP Tokens V1 and V2, non-zero to non-zero approvals are prohibited. Instead, after every non-zero approval, the allowance for the spender must be reset to 0.

Minter Methods

The following methods are only callable by the minter (private attribute).

Note

For Curve Token V1, the minter attribute is not public.

CurveToken.mint(_to: address, _value: uint256)

Mint an amount of the token and assign it to an account. This encapsulates the modification of balances such that the proper events are emitted.

  • _to: Address that will receive the created tokens

  • _value: Amount that will be created

CurveToken.burn(_value: uint256)

Burn an amount of the token of msg.sender.

  • _value: Token amount that will be burned

CurveToken.burnFrom(_to: address, _value: uint256)

Burn an amount of the token from a given account.

  • _to: Account whose tokens will be burned

  • _value: Amount that will be burned

CurveToken.set_minter(_minter: address)

Set a new minter for the token.

  • _minter: Address of the new minter

Curve Token V2

The implementation for a Curve Token V2 may be viewed on GitHub.

Note

Compared to Curve Token v1, the following changes have been made to the API:

  • minter attribute is public and therefore a minter getter has been generated

  • name and symbol attributes can be set via set_name

  • mint method returns bool

  • burnFrom method returns bool

  • burn method has been removed

Warning

For Curve LP Tokens V1 and V2, non-zero to non-zero approvals are prohibited. Instead, after every non-zero approval, the allowance for the spender must be reset to 0.

CurveToken.minter() → address: view

Getter for the address of the minter of the token.

CurveToken.set_name(_name: String[64], _symbol: String[32])

Set the name and symbol of the token.

  • _name: New name of token

  • _symbol: New symbol of token

This method can only be called by minter.

CurveToken.mint(_to: address, _value: uint256)bool

Mint an amount of the token and assign it to an account. This encapsulates the modification of balances such that the proper events are emitted.

Returns True if not reverted.

CurveToken.burnFrom(_to: address, _value: uint256)bool

Burn an amount of the token from a given account.

  • _to: Account whose tokens will be burned

  • _value: Amount that will be burned

Returns True if not reverted.

Curve Token V3

The Curve Token V3 is more gas efficient than versions 1 and 2.

Note

Compared to the Curve Token V2 API, there have been the following changes:

  • increaseAllowance and decreaseAllowance methods added to mitigate race conditions

The implementation for a Curve Token V3 may be viewed on GitHub.

CurveToken.increaseAllowance(_spender: address, _added_value: uint256)bool

Increase the allowance granted to _spender by the msg.sender.

This is alternative to approve that can be used as a mitigation for the potential race condition.

  • _spender: Address which will transfer the funds

  • _added_value: Amount of to increase the allowance

Returns True if success.

CurveToken.decreaseAllowance(_spender: address, _subtracted_value: uint256)bool

Decrease the allowance granted to _spender by the msg.sender.

This is alternative to {approve} that can be used as a mitigation for the potential race condition.

  • _spender: Address which will transfer the funds

  • _subtracted_value: Amount of to decrease the allowance

Returns True if success.