FunC language overview

FunC is an intermediate-level language used to write smart contracts on TON. It is a domain-specific, statically typed language with C-like syntax. Example of a FunC method for sending funds:

() send_money(slice address, int amount) impure inline {
    var msg = begin_cell()
        .store_uint(0x10, 6) ;; It sets the message to be non-bounceable.
        .store_slice(address)
        .store_coins(amount)
        .end_cell();

    send_raw_message(msg, 64);
}

The method receives two parameters: the address to send the money to, and the amount to send. It does not return a value, indicated by () to the left of the method name send_money.

The method uses the impure and inline specifiers, which are flags that tell the compiler to process the method in specific ways.

The method first creates the message to send msg by using a cell builder, since the message is encoded as a cell. The procedure is:

1. Create a new cell builder with begin_cell.
2. Set message flags at the line with the single-line comment ;; It sets the message to be non-bounceable..
3. Store the receiving address with store_slice.
4. Store the amount to send using store_coins.
5. Finalize the cell with a call to the end_cell function.

Finally, function send_raw_message sends the message, where the parameter 64 describes a sending mode.

Compiler

The compiler converts FunC programs into Fift assembler code. The Fift assembler code is then compiled down to bitcode for the TON Virtual Machine using the Fift compiler.

Developers can use the compiled bitcode, structured as a bag of cells like all data in the TON blockchain, to test smart contracts, send messages, or execute it in a local TVM instance.

Compile using tooling

To compile FunC files to bitcode, install the func-js npm package in your project folder. It runs in any environment with Node.js v22 or later installed.

The func-js package integrates the FunC and Fift compilers to produce bitcode directly from FunC source code, without manual Fift invocation.

To install func-js, run the following command in your project root:

npm i @ton-community/func-js

Next, run the following command to compile a specific FunC file:

npx func-js ./contract.fc --boc ./output.boc

where contract.fc is the FunC source file in your project root, and output.boc is the compiled bitcode output.

You can also use Blueprint to start a project. See the Blueprint section for setup instructions.

Compile manually using the binaries

Prebuilt FunC compiler binaries for Windows, macOS (Intel or Arm64), and Ubuntu are available on GitHub.

1. Download the corresponding binary for your operating system:

• Linux: func-linux-x86_64 (Intel/AMD) and func-linux-arm64 (Arm64)
• Mac: func-mac-x86-64 (Intel/AMD) and func-mac-arm64 (Arm64)
• Windows: func.exe

Rename the executable, for example, to func, for easier use in the command line, and add it to your system’s PATH.

2. Download the FunC standard library.

Get the smartcont_lib.zip from the same GitHub, extract it, and copy stdlib.fc to your project root.

3. Compile a FunC file to Fift assembler code.

Run the following command in your project root:

func contract.fc -o output.fif

where contract.fc is the FunC file to compile, and output.fif is the generated Fift output.

If you need to compile the generated Fift file output.fif further down to TVM bitcode, use the Fift compiler. See the Fift for download and usage instructions.

Tutorials

• Challenge 1: Simple NFT deploy

• Challenge 2: Chatbot contract

• Challenge 3: Jetton vending machine

• Challenge 4: Lottery/raffle

• Challenge 5: Create UI to interact with the contract in 5 minutes

• Challenge 6: Analyzing NFT sales on the Getgems marketplace

• TON hello world Part 2: guide for writing your first smart contract

• TON hello world Part 4: guide for testing your first smart contract

• 10 lessons for developing contracts in FunC — Russian version

• FunC quiz — a short Telegram quiz focused on FunC, with a few general TON questions.

Contests

You can review past competitions to learn more:

Contest	Tasks	Solutions
TSC #5 (Dec 2023)	Tasks	—
TSC #4 (Sep 2023)	Tasks	1 2 3 4
TSC #3 (Dec 2022)	Tasks	Solutions
TSC #2 (Jul 2022)	Tasks	Solutions
TSC #1 (Mar 2022)	Tasks	Solutions

Changelog

History of FunC