"Ich bin im Restaurant."

Translation: I am in the restaurant.

[Axiome]

in + dem = im, voila un bel exemple de contraction.

[DP618SLG]

Why it is only 'in the restaurant'. Im can be 'in einem', i.e. 'in a restaurant' as well

[slendro]

There is a slight problem with the non-equivalence of prepositions between languages here. In English, though being "in" a restaurant is correct, wouldn't saying "at" a restaurant be much more usual?

[PeaceJoyPancakes]

It's contextual, no? In English, anyway. We're at the restaurant. I'm in the restaurant, waiting to be seated. My friend is outside the restaurant, finishing his cigarette.

Is the German "im" used for both the "in" and "at" meanings?