Perhaps one day you walk into a pet shop and say to the salesperson, “I want a male cat, neutered, either white or tan; or a female cat, neutered, any color but white; or I’ll take any cat you have as long as it’s black.” And the salesperson says to you, “So you want a cat from the class of cats represented by the following expression: (M x N x (W + T)) + (F x N x (1 – W)) + B Right?” And you say, “Yes! Exactly!”
