This semester at the VUA, I am teaching a minicourse on basic stream calculus with applications to the theory of (signal) flow graphs. In my ACG talk, I shall give a summary of the latter. It will include the following proposition:

a function f: IR^omega -> IR^omega is implementable by a stream circuit built from the following four primitives: adder copier register (delay) multiplier (with a constant)

if and only if:

f(sigma) = rho x sigma (for all sigma)

(where x denotes convolution product of streams) for some rational stream rho.