There seems to be a bit of a confusion between "Analogue / Digital" (Types of electronic and other signal processing) and "Continuous / Discrete" (variables). Maths can handle integers, (the only discrete variables) rational, irrational and transcendental variables and all types turn up in Science.
Between Scientists and Science there is always the 'measurement barrier'. Every measurement has a certain resolution and accuracy and, as soon as we write it down or process it in a digital processor, it becomes a discrete quantity.
Before digital processors had sufficient capacity, we used to employ Analogue Computers which would take the analogue values from sensors and potential dividers and, with clever use of Op Amps, would produce an Analogue output signal. The whole information chain used continuous variables (Volts and current values). However, of course there was noise /hum / drift etc and the output value was not an 'exact' outcome. So you could not actually rely on a set of monotonic input variables giving you a monotonic answer.