Quotes About Covariant

arrays are covariant. This scary-sounding word means simply that if Sub is a subtype of Super, then the array type Sub[] is a subtype of the array type Super[]. Generics, by contrast, are invariant: for any two distinct types Type1 and Type2, List is neither a subtype nor a supertype of List. You might think this means that generics are deficient, but arguably it is arrays that are deficient.

The world, particles, light, energy, space, and time—all of this is nothing but the manifestation of a single type of entity: covariant quantum fields.

The general laws of nature are to be expressed by equations that hold true for all systems of coordinates, that is they are covariant with respect to any substitutions whatever.