Just testing some stuff. Here's some code for Haskell's Functor typeclass:

class  Functor f  where
  fmap  :: (a -> b) -> f a -> f b
  (<$)  :: a -> f b -> f a
  (<$)  =  fmap . const

And here is some math:

$$ \begin{align} \cdots\rightarrow H_{n+1}(X)\,&\xrightarrow{\partial_*}\,H_{n}(A\cap B)\,\rightarrow\,H_{n}(A)\oplus H_{n}(B)\,\rightarrow\,H_{n}(X)\xrightarrow{\partial_*}\\ &\quad\xrightarrow{\partial_*}\,H_{n-1} (A\cap B)\rightarrow \cdots\rightarrow H_0(A)\oplus H_0(B)\,\rightarrow\,H_0(X)\rightarrow\,0. \end{align} $$