\mod, quotient structures, and spacing [duplicate]

Possible Duplicate:
typesetting modulus operator, as in remainder

When \mod is used in

a \cong b \mod c


the extra space between \mod and what precedes it is appropriate. But what if I want to write about the quotient structure \mathbb R\mod {2\pi}? In that case \mod is more like a binary operator. How should one code this to get something with spacing appropriate to the occasion?

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marked as duplicate by Werner, Thorsten, egreg, Stefan Kottwitz♦Dec 21 '12 at 7:44

$$....$$ is depricated. Use $...$ instead. – A.Ellett Dec 21 '12 at 2:49
@MichaelHardy Additionally to \mod{<arg>}, there’s \bmod, \pmod{<arg>} and \pod{<arg>}. Take a look at the amsmath manual (texdoc amsldoc, page 18 (pdf 22), section 5.2). – Qrrbrbirlbel Dec 21 '12 at 3:39
The binary-operator version of \mod is \bmod.