presto-main/src/main/java/io/prestosql/operator/scalar/StringFunctions.java/StringFunctions/chr
class StringFunctions:    @Description("convert Unicode code point to a string")
    @ScalarFunction
    @SqlType("varchar(1)")
    public static Slice chr(@SqlType(StandardTypes.BIGINT) long codepoint)
    {
        try {
            return SliceUtf8.codePointToUtf8(Ints.saturatedCast(codepoint));
        }
        catch (InvalidCodePointException e) {
            throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "Not a valid Unicode code point: " + codepoint, e);
        }
    }