This block detects positive and negative peaks of differentiable and non-differentiable input signals without sampling.
For differentiable input signals, an extremum is detected if the derivative of the input signal is zero.
To handle non-differentiable input signals, the input signal u is conditioned by a first order with time constant T.
Like in the derivative block,
the derivative of the input signal is approximated by (u - x)/T.
This way even steps with local extrema just before and after the step are taken into account.
Additionally, when the simulation terminates, y_min and y_max are updated.