FunC comments

The official smart contract language of TON Blockchain is Tolk. FunC is now a legacy language, with its compiler no longer maintained.

FunC pages will be moved down in the sidebar in mid-April 2026. Here is the preview of a possible future placement, right between "Blockchain foundations" and "Contribute" sections:

Learn how to migrate from FunC to Tolk.

FunC supports both single-line and multi-line comments.

Single-line comments start with a double semicolon ;;. For example:

int x = 1; ;; assigns 1 to x

Multi-line comments begin with an opening curly brace and dash {- and end with a dash and closing curly brace -}. Unlike other languages, FunC allows nested multi-line comments.

Example:

{- This is a multi-line comment
    {- This is a comment inside a comment -}
-}

Single-line comments ;; can also appear inside multi-line comments. They take precedence over the multi-line comments {- -}.

For example, in the following snippet, const a = 10; is inside a multi-line comment and is effectively commented out:

{-
  Start of the comment

;; This comment’s ending is itself commented out -> -}

const a = 10;

;; This comment’s beginning is itself commented out -> {-

  End of the comment
-}