Aplicación lineal en LaTeX

\begin{eqnarray}
   \mathit{f}:\mathcal{C}&\longrightarrow&\mathbf{R}\nonumber\\
   x&\rightarrow&f(x) = \left\{
   \begin{array}{l@{\quad}l}
    \exp(1+x^2), & \mbox{si } x \geq 0\\
    0, & \mbox{si } x < 0 
   \end{array}
   \right.
\end{eqnarray}