# Pair (ERC-20)

This documentation covers ERC-20 functionality for denominating pool tokens. For Uniswap-specific functionality, see Pair.

## Code

[`UniswapV2ERC20.sol`](https://github.com/Uniswap/uniswap-v2-core/blob/master/contracts/UniswapV2ERC20.sol)

## Events

### Approval

```solidity
event Approval(address indexed owner, address indexed spender, uint value);
```

Emitted each time an approval occurs via [approve](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference) or [permit](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference).

### Transfer

```solidity
event Transfer(address indexed from, address indexed to, uint value);
```

Emitted each time a transfer occurs via [transfer](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference), [transferFrom](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference), mint, or burn.

## Read-Only Functions

### name

```solidity
function name() external pure returns (string memory);
```

Returns `Uniswap V2` for all pairs.

### symbol

```solidity
function symbol() external pure returns (string memory);
```

Returns `UNI-V2` for all pairs.

### decimals

```solidity
function decimals() external pure returns (uint8);
```

Returns `18` for all pairs.

### totalSupply

```solidity
function totalSupply() external view returns (uint);
```

Returns the total amount of pool tokens for a pair.

### balanceOf

```solidity
function balanceOf(address owner) external view returns (uint);
```

Returns the amount of pool tokens owned by an address.

### allowance

```solidity
function allowance(address owner, address spender) external view returns (uint);
```

Returns the amount of liquidity tokens owned by an address that a spender is allowed to transfer via [transferFrom](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference).

### DOMAIN\_SEPARATOR

```solidity
function DOMAIN_SEPARATOR() external view returns (bytes32);
```

Returns a domain separator for use in [permit](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference).

### PERMIT\_TYPEHASH

```solidity
function PERMIT_TYPEHASH() external view returns (bytes32);
```

Returns a typehash for use in [permit](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference).

### nonces

```solidity
function nonces(address owner) external view returns (uint);
```

Returns the current nonce for an address for use in [permit](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference).

## State-Changing Functions

### approve

```solidity
function approve(address spender, uint value) external returns (bool);
```

Lets `msg.sender` set their allowance for a spender.

* Emits [Approval](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference).

### transfer

```solidity
function transfer(address to, uint value) external returns (bool);
```

Lets `msg.sender` send pool tokens to an address.

* Emits [Transfer](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference).

### transferFrom

```solidity
function transferFrom(address from, address to, uint value) external returns (bool);
```

Sends pool tokens from one address to another.

* Requires approval.
* Emits [Transfer](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference).

### permit

```solidity
function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;
```

Sets the allowance for a spender where approval is granted via a signature.

* See Using Permit.
* Emits [Approval](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference).

## Interface

```solidity
import '@uniswap/v2-core/contracts/interfaces/IUniswapV2ERC20.sol';
```

```solidity
pragma solidity >=0.5.0;

interface IUniswapV2ERC20 {
  event Approval(address indexed owner, address indexed spender, uint value);
  event Transfer(address indexed from, address indexed to, uint value);

  function name() external pure returns (string memory);
  function symbol() external pure returns (string memory);
  function decimals() external pure returns (uint8);
  function totalSupply() external view returns (uint);
  function balanceOf(address owner) external view returns (uint);
  function allowance(address owner, address spender) external view returns (uint);

  function approve(address spender, uint value) external returns (bool);
  function transfer(address to, uint value) external returns (bool);
  function transferFrom(address from, address to, uint value) external returns (bool);

  function DOMAIN_SEPARATOR() external view returns (bytes32);
  function PERMIT_TYPEHASH() external pure returns (bytes32);
  function nonces(address owner) external view returns (uint);

  function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;
}
```

## ABI

```typescript
import IUniswapV2ERC20 from '@uniswap/v2-core/build/IUniswapV2ERC20.json'
```

<https://unpkg.com/@uniswap/v2-core@1.0.0/build/IUniswapV2ERC20.json>