> For the complete documentation index, see [llms.txt](https://boncurs.gitbook.io/boncurs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://boncurs.gitbook.io/boncurs/boncurs-bonding-curve-library/exponential-curves/expcurve.md).

# ExpCurve

[Git Source](https://github.com/dustinstacy/boncurs/blob/7928cae257b46ede89b50d06eaae18601fcd0340/contracts/exponential/ExpCurve.sol)

**Inherits:** BancorFormula

This contract is used to get the purchase and sale return values for an exponential curve.

## Functions

### getPurchaseReturn

Returns the purchase value using an Exponential Curve.

```solidity
function getPurchaseReturn(uint256 supply, uint256 reserveBalance, uint32 reserveRatio, uint256 depositAmount)
    internal
    view
    returns (uint256 purchaseReturn);
```

**Parameters**

| Name             | Type      | Description                  |
| ---------------- | --------- | ---------------------------- |
| `supply`         | `uint256` | token total supply           |
| `reserveBalance` | `uint256` | balance of the reserve token |
| `reserveRatio`   | `uint32`  | reserve ratio of the token   |
| `depositAmount`  | `uint256` | amount of tokens to purchase |

**Returns**

| Name             | Type      | Description            |
| ---------------- | --------- | ---------------------- |
| `purchaseReturn` | `uint256` | cost of the conversion |

### getSaleReturn

Returns the sale value using an Exponential Curve.

```solidity
function getSaleReturn(uint256 supply, uint256 reserveBalance, uint32 reserveRatio, uint256 sellAmount)
    internal
    view
    returns (uint256 saleReturn);
```

**Parameters**

| Name             | Type      | Description                  |
| ---------------- | --------- | ---------------------------- |
| `supply`         | `uint256` | token total supply           |
| `reserveBalance` | `uint256` | balance of the reserve token |
| `reserveRatio`   | `uint32`  | reserve ratio of the token   |
| `sellAmount`     | `uint256` | amount of tokens to sell     |

**Returns**

| Name         | Type      | Description              |
| ------------ | --------- | ------------------------ |
| `saleReturn` | `uint256` | return of the conversion |