South Africa was trying this when I moved away about 15 years ago. If you wanted to smoke you had to sit in separate closed off area in restaurants (for example).

No idea what the ultimate outcome of that was though.

Edit: According to smokefreeworld.org:

The adult smoking rate declined from 27.1 percent in 2000 to 18.2 percent in 2012

I’ll happily pick a side as a kid who grew up in a house constantly full of smoke and a parent who’s a total mess at least partially because of this. Good. It’s about time some serious steps were taken. Not to mention the effects of second hand smoke.