# Pair Addresses

## getPair <a href="#getpair" id="getpair"></a>

The most obvious way to get the address for a pair is to call getPair on the factory. If the pair exists, this function will return its address, else `address(0)` (`0x0000000000000000000000000000000000000000`).

* The “canonical” way to determine whether or not a pair exists.
* Requires an on-chain lookup.

## CREATE2 <a href="#create2" id="create2"></a>

Thanks to some [fancy footwork in the factory](https://github.com/SwipeWallet/swipe-swap/blob/master/contracts/uniswapv2/UniswapV2Factory.sol#L30), we can also compute pair addresses *without any on-chain lookups* because of [CREATE2](https://eips.ethereum.org/EIPS/eip-1014). The following values are required for this technique:

|                        |                                                                                     |
| ---------------------- | ----------------------------------------------------------------------------------- |
| `address`              | The [factory address](https://uniswap.org/docs/v2/smart-contracts/factory/#address) |
| `salt`                 | `keccak256(abi.encodePacked(token0, token1))`                                       |
| `keccak256(init_code)` | `0x96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f`                |

* `token0` must be strictly less than `token1` by sort order.
* Can be computed offline.
* Requires the ability to perform `keccak256`.

### Examples <a href="#examples" id="examples"></a>

#### Solidity <a href="#solidity" id="solidity"></a>

```
address factory = 0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f;
address token0 = 0xCAFE000000000000000000000000000000000000; // change me!
address token1 = 0xF00D000000000000000000000000000000000000; // change me!

address pair = address(uint(keccak256(abi.encodePacked(
  hex'ff',
  factory,
  keccak256(abi.encodePacked(token0, token1)),
  hex'96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f'
))));
```