FoxRabbitWithInit

The Modelica By Example page does not show the code for the usage comparison, but it does give this patch diagram:

The exported complete Modelica code for the SysML/SysPhS block FoxRabbitWithInit is:

model FoxRabbitWithInit
  FoxRabbitWithInit _FoxRabbitWithInit;
  model FoxRabbitWithInit
    RegionalPopulation f;
    RegionalPopulation r;
    Starvation fS(gamma.start=0.4,gamma.fixed=true);
    Reproduction rR(alpha.start=0.1,alpha.fixed=true);
    Predation fP(beta.start=0.02,beta.fixed=true,delta.start=0.02,delta.fixed=true);
  equation
    connect(fS.s,f.s);
    connect(fP.b,f.s);
    connect(fP.a,r.s);
    connect(r.s,rR.s);
  end FoxRabbitWithInit;
  model RegionalPopulation
    SpeciesFlowElement s;
    Population p(start=10.0,fixed=true);
    parameter Population p0;
  equation
    der(p)=s.r;
    p=s.p;
  end RegionalPopulation;
  model Starvation
    extends SinkOrSource;
    parameter Rate gamma;
  equation
    decline=gamma*s.p;
  end Starvation;
  model Reproduction
    extends SinkOrSource;
    parameter Rate alpha;
  equation
    growth=alpha*s.p;
  end Reproduction;
  model Predation
    extends Interaction;
    parameter Rate beta;
    parameter Rate delta;
  equation
    b_growth=delta*a.p*b.p;
    a_decline=beta*a.p*b.p;
  end Predation;
  connector SpeciesFlowElement
    Population p;
    flow Rate r;
  end SpeciesFlowElement;
  model SinkOrSource
    Rate growth;
    Rate decline;
    SpeciesFlowElement s;
  equation
    decline=-growth;
    s.r=decline;
  end SinkOrSource;
  model Interaction
    SpeciesFlowElement a;
    SpeciesFlowElement b;
    Rate a_growth;
    Rate a_decline;
    Rate b_growth;
    Rate b_decline;
  equation
    a_decline=-a_growth;
    a.r=a_decline;
    b_decline=-b_growth;
    b.r=b_decline;
  end Interaction;
  type Population=Real;
  type Rate=Real(unit="1/s");
end FoxRabbitWithInit;