> For the complete documentation index, see [llms.txt](https://sinqlarity.gitbook.io/sinqlarity-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://sinqlarity.gitbook.io/sinqlarity-docs/contract-details/whitelist.md).

# WHITELIST

### DESCRIPTION

The whitelist contract allows users to add their addresses to a whitelist. Only non-whitelisted addresses can be added, and the number of whitelisted addresses cannot exceed the maximum limit. The contract provides a function to add an address to the whitelist and another function to check if an address is already whitelisted. It offers a basic mechanism for managing whitelisted addresses.

### FUNCTIONS

1. **addAddressToWhitelist() public:** This function allows the sender (caller) to add their address to the whitelist. It performs the following steps:

* Checks if the sender's address is not already whitelisted.
* It checks if the maximum number of whitelisted addresses (maxWhitelistedAddresses) has not been reached.
* Adds the sender's address to the whitelistedAddresses mapping by setting it to true.
* Increments the numAddressesWhitelisted variable.

2. **checkAddress(address user) public view returns(bool):** This function checks whether a given address is whitelisted or not. It takes an address as input and returns a boolean value indicating whether the address is whitelisted (true) or not (false).
3. **numAddressesWhitelisted()**
4. **maxWhitelistedAddresses()**

### EXTRA PARAMETERS

**Contract Level:** Easy

**Utility Tags:** Whitelist , Address Whitelist, Access Control

1. **maxWhitelistedAddresses: Integer**

### USES

1. **Token Sales:** A whitelist can be used to ensure that only whitelisted addresses can participate in a token sale or contribute to a crowdfunding campaign.
2. **Restricted Features:** Certain features or functionalities of a decentralized application (dApp) can be limited to whitelisted addresses, allowing only authorized users to access or use them.
3. **Membership Systems:** Whitelisting addresses can be employed to create membership systems where only whitelisted members can access specific resources, services, or events.
4. **Administrative Actions:** The contract can make administrative actions or control over some parts of a system easier by whitelisting certain addresses. For example, it can give authorized participants special rights or privileges.
5. **Compliance and Regulation:** Whitelisting can assist in adhering to regulatory requirements by allowing only verified or approved addresses to perform certain activities within a system.