- rabbits -

This file calculates the birth rate, death rate, and 
population of rabbits.


-- rabbit_births --

rabbit_births[ t ] is the
number of rabbits born during time t.

  table rabbit_births : time -> general.

  rabbit_births[ t ] = 
    number_of_rabbits[ t ] *
    birth_rate_of_rabbits[] * 
    ( 1 - number_of_rabbits[ t ] / limit_of_rabbit_population[] ) * 
    0.01.


-- rabbit_deaths --

rabbit_deaths[ t ] is the
number of rabbits killed during time t.

  table rabbit_deaths : time -> general.

  rabbit_deaths[ t ] = 
    number_of_rabbits[ t ] *
    death_rate_of_rabbits[] *
    number_of_foxes[ t ] *
    0.0005.


-- number_of_rabbits --

number_of_rabbits[ t ] is the population
of rabbits at time t.

  table number_of_rabbits : time -> general.

  number_of_rabbits[ 1 ] = 
    initial_number_of_rabbits[].

  number_of_rabbits[ t>1 ] = 
    number_of_rabbits[ t-1 ] + 
    rabbit_births[ t-1 ] - 
    rabbit_deaths[ t-1 ].


--- initial_number_of_rabbits ---

initial_number_of_rabbits[] is the rabbit
population at time 1. This is input by the user.

  table initial_number_of_rabbits : -> general.

  initial_number_of_rabbits[] = 
    1000.


--- birth_rate_of_rabbits ---

birth_rate_of_rabbits[] is the proportion
of rabbits born in a year. It is
input
by the user.

  table birth_rate_of_rabbits : -> general.

  birth_rate_of_rabbits[] = 
    5.


--- death_rate_of_rabbits ---

death_rate_of_rabbits[]  is the proportion
of rabbits that die in a year. It is input
by the user.

  table death_rate_of_rabbits : -> general.

  death_rate_of_rabbits[] = 
    5.


--- limit_of_rabbit_population ---

limit_of_rabbit_population[] is the maximum
number of rabbits allowed. This is input by the user.

  table limit_of_rabbit_population : -> general.

  limit_of_rabbit_population[] = 
    10000.