IDENTIFICATION DIVISION
PROGRAM-ID TwoRaindrops
VERSION 20240131
COMMENT Two raindrops of same size and altitude are falling from a cloud.
COMMENT How long does it take until the touch?
COMMENT s'' = -2*gamma*m/s^2

ENVIRONMENT DIVISION
ENGINE Anabrid-THAT
TIMEBASE 1ms
REQUIRES COEFFICIENT 3, INVERTER 1, INTEGRATOR 2, COMPARATOR 1, MULTIPLIER 2, OPEN-AMP 1 

DATA DIVISION
OUTPUT OUTPUT.X s_limited
COEFFICIENT.1 2*radius of the raindrop
COEFFICIENT.2 initial distance -s0
COEFFICIENT.3 2*gamma*m

PROGRAM DIVISION
+1 -> COEFFICIENT.1 -> 2r
2r -> INVERTER.1 -> -2r
-1 -> COEFFICIENT.2 -> -s0
+1 -> COEFFICIENT.3 -> 2gamma*m
s'' -> INTEGRATOR.1 -> -s'
-s', IC:-s0 -> INTEGRATOR.2 -> s

# The raindrops may only approach until they touch. Our model does not include their unification
A:s, B:-2r, GT0:s, LT0:2r -> COMPARATOR.1 -> s_limited

s_limited,s_limited -> MULTIPLIER.1 -> s^2

# division 2gamma*m / s^2
# Open amplifier is realized on THAT by FB:SUMMER.GND -> SUMMER
2gamma*m, inp2 -> OPEN-AMP -> -2gamma*m/s^2=s''
2gamma*m^2, s^2 -> MULTIPLIER.2 -> inp2

OPERATION DIVISION
MODE REPEAT
OP-TIME 12ms