No. Absolutely not. When I eat here in the Summer I wear shorts and a polo.
No, you'll see people dressed in jeans and a nice shirt to a table wearing suits. But most people are smartly dressed. I've noticed people just having a drink at the bar tend to be more sharply dressed. In cooler weather I would not show up dressed like a slob or you'll feel out of place. Summertime is much more casual, especially when dining on the terrace with the "windows" open to the square.
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