double RandGen::RandReal(double dmin, double dmax)
// precondition: dmin <= dmax
// postcondition: returns double in [dmin..dmax)
{
double width = dmax - dmin;
return RandReal() * width + dmin;
}
double RandGen::RandBell(double average)
//precondition: average<0
//postcondition: returns double in [0..high value)
// return values are normall distributed
{
double fac,r,v1,v2,value;
do{
v1=2.0*RandReal()-1.0;
v2=2.0*RandReal()-1.0;
r=v1*v1+v2*v2;
}while(r>=1.0 || r==0.0);
fac=sqrt(-2.0*log(r)/r);
value=(average+(v1*fac)*(average*.25));
if(value<0)
return 0;
else
return value;
}
int RandGen::RandInt(int max)
// precondition: max > 0
// postcondition: returns int in [0..max)
{
return int(RandReal() * max);
}
