Pros:
- it is convenient to type and read numbers this way;
- Ada, Perl, C++, Go and Rust already support that;
- can support thousands as well as lakhs and crores;

Cons:
- standard SQL does not have this support;
- PostgreSQL treat `SELECT 1_000_000` as number one with `_000_000` alias: http://sqlfiddle.com/#!17/0a28f/400
- C++ has `1'000'000` instead of `1_000_000`;

What do you think?

{
    assert(node);
    ASTFunction & function = dynamic_cast<ASTFunction &>(*node);
    
    
    if (pos->type != TokenType::OpeningRoundBracket)
    {
        ASTPtr window_name_ast;
        ParserIdentifier window_name_parser;
        if (window_name_parser.parse(pos, window_name_ast, expected))
        {
            function.window_name = getIdentifierName(window_name_ast);
            return true;
        }
        else
        {
            return false;
        }
    }
    
    
    ParserWindowDefinition parser_definition;
    return parser_definition.parse(pos, function.window_definition, expected);
}
static bool tryParseFrameDefinition(ASTWindowDefinition * node, IParser::Pos & pos,