pool-templates

curve-contract/contracts/pool-templates

Contract templates used as the basis for future pools.

Subdirectories

Each subdirectory holds contracts and other files specific to a single Curve pool template.

• [a]: Pool implementation with aToken-style lending (i.e., interest accrues as balance increases)
• [base]: Minimal pool implementation optimized for no lending
• [eth]: Pool implementation with ETH
• [meta]: Metapool implementation for swapping base assets against a Curve LP token
• [y]: Pool implementation with yearn-style lending (i.e., interest accrues as rate increases)

Development

Working with Templates

Contracts in this subdirectory contain special triple-dunder variables which are modified according to the quantity and properties of each stablecoin in a pool.

• ___USE_LENDING___: Array of booleans indicating whether each underlying coin in the pool is lent on the associated lending protocol
• ___N_COINS___: The number of coins within the pool
• ___PRECISION_MUL___: Array of integers that coin balances are multiplied by in order to adjust their precision to 18 decimal places
• ___RATES___: Array of integers indicating the relative value of 1e18 tokens for each stablecoin

Metapools also make use of the following variables:

• ___BASE_N_COINS___: The number of coins within the base pool
• ___BASE_PRECISION_MUL___: Array of integers that base coin balances are multiplied by to adjust their precision to 18 decimal places
• ___BASE_RATES___: Array of integers indicating the relative walue of 1e18 tokens for each base pool stablecoin

These variables are substituted out at compile-time. To set the values, edit the pooldata.json file within the template directory.

The layout of a template's pooldata.json is similar to that of an actual pool, but less fields are required:

{
    "wrapped_contract": "yERC20",   // mock wrapped coin contract to use, from `contracts/testing`
    "base_pool_contract": ""        // for metapool templates, use this contract for the base pool
    "coins": [                      // each list item represents 1 swappable coin within the pool
        {
            "decimals": 18,          // number of decimal places for the underlying coin
            "tethered": false,       // does the token contract return `None` on a successful transfer/approve?
            "wrapped": true,         // is wrapping used for this coin?
            "wrapped_decimals": 18,  // decimal places for the wrapped coin - can be omitted if wrapped == false
        },
    ]
    "rate_calculator_address": ""    // address of exchange rate calculator for pools with unique logic
}

Note: For y and a pools, the implementor may have to remove/change some small parts in the template code which is specific to yearn and aave pools.

The rate_calcultor_address is used when adding a pool to the Curve Pool Registry.