{
    checker.cal

    no need for input variables
}

{ stripe and checker functions }
{stripew = 0.5;}
stripew = 1.7;
scalex(x) = 0.5*x/stripew;
{ stripe(x) = if (0.5*x - 0.5 - floor(0.5*x),1.0,0.0); }
stripe(x) = if (scalex(x) - 0.5 - floor(scalex(x)),1.0,0.0);
checker(x,y) = if (stripe(x)-0.5,stripe(y),1.0-stripe(y));

brite = checker(Px,Py);