/*
* This problem is intended to introduce some basic concepts about inheritance.
*/
class Block {
}
class HeavyBlock : Block {
real weight;
HeavyBlock(real weight) : weight(weight) {}
}
Block b0 = new Block();
Block b1 = new Block(), b2 = new Block();
HeavyBlock b3 = new HeavyBlock(3.5);
// a variable whose domain contains all the Block's instances..
Block b;
// removes from `b` the `b0` instance..
b != b0;