  We consider the initial boundary value problem for the focusing nonlinear
Schr\"odinger equation in the quarter plane $x>0,t>0$ in the case of decaying
initial data (for $t=0$, as $x\to +\infty$) and the Robin boundary condition at
$x=0$. We revisit the approach based on the simultaneous spectral analysis of
the Lax pair equations [Fokas, 2002; Fokas, Its, Sung, 2005] and show that the
approach can be implemented without any a priori assumptions on the long-time
behavior of the boundary values.
