Generating a Discrete Version of a Signal

How would I generate the discrete version of x(t) = A cos(omega t ) (u(t) - u(t-tau)) ?

I am unsure of how the u(t) - u(t-tau) part.

[gonzalo Mier]

The u(t) - u(t-tau) can be done as

heaviside(t) - heaviside(u-tau)

https://www.mathworks.com/help/symbolic/heaviside.html