Hello World

This is probably the simplest possible Tact program. It will provide callers with the classic output "hello world".

Tact lets you write smart contracts. This code defines a single contract named HelloWorld. Smart contracts must be deployed to the blockchain network to be usable, try to deploy this contract by pressing the Deploy button.

Contract deployments usually cost gas. This website deploys to an emulator of TON blockchain, so gas is emulated TON coin (which is free).

If you're unfamilar with terms like contract, deployment and gas, please read this post first. It's a great introduction to all blockchain terminology you will need to learn Tact.

A simple interaction

Contracts can have getters like greeting(). Getters are special external interface functions that allow users to query information from the contract. Try to call the getter by pressing the Get greeting button. Calling getters is free and does not cost gas.

Don't worry if some things aren't clear now, we will dive into getters in more detail later.

All Examples

contract Counter {
 
    // persistent state variable of type Int to hold the counter value
    val: Int as uint32;
 
    // initialize the state variable when contract is deployed
    init() {
        self.val = 0;
    }
 
    // handler for incoming increment messages that change the state
    receive("increment") {
        self.val = self.val + 1;
    }
 
    // read-only getter for querying the counter value
    get fun value(): Int {
        return self.val;
    }
}