Do Solidity smart contract symbols support unicode?

Question

In a smart contract where the token name and symbol are defined, is unicode supported or should these be ASCII only characters?

As below, would it be a valid contract or token symbol?

    constructor() public
    ERC721("✕ray Ýour ℤen", "✕Ýℤ")  
    {
        _setBaseURI("https://foo.foo");
    }

Answer 1

As mentioned by Linum Labs, that approach can be used for Solidity v 0.7 and higher. If you want to use an older version,

From docs:

\uNNNN (Unicode escape)

You will need to convert Unicode character to escape sequence, for example:

✕ray Ýour ℤen

will be

\u2715ray \u00ddour \u2124en

And Important NOTE from docs:

Any Unicode line terminator which is not a newline (i.e. LF, VF, FF, CR, NEL, LS, PS) is considered to terminate the string literal. Newline only terminates the string literal if it is not preceded by a \.

Answer 2

Welcome!

Just as a quick note, you mention "smart contracts" in the question, but give code that looks like Solidity, and also have a Solidity tag in your question, so I assume that the question's focus is Solidity. Different languages may handle Unicode differently, so the answer can change from language to language.

Solidity (v0.7 and higher)

(see hack3r_0m's answer for older versions of Solidity)

From the docs:

While regular string literals can only contain ASCII, Unicode literals – prefixed with the keyword unicode – can contain any valid UTF-8 sequence. They also support the very same escape sequences as regular string literals.

string memory a = unicode"Hello 😃";

This means the code as provided in the question would not work (regular strings are ASCII-encoded), but that by prefacing the string with unicode, it should work.

Vyper

In Python 3.x the built-in string type uses utf-8 encoding. As such, our assumption is that Unicode characters should be natively supported in strings. Remix seems to be down for us at the moment, so we don't have a simple way to test this at the moment.

Answer 3

Nope, write (unicode"✕ray Ýour ℤen",unicode"✕Ýℤ"). e.g.

ERC721(unicode"✕ray Ýour ℤen", unicode"✕Ýℤ"){
   _setBaseURI("https://foo.foo");
}

actully openzeppelin is updated, now code will look like:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";

contract RayYourEn is ERC721 {
    constructor() ERC721(unicode"✕ray Ýour ℤen", unicode"✕Ýℤ") {}

    function _baseURI() internal pure override returns (string memory) {
        return "https://foo.foo";
    }
}```