// returns the number of elements copied, which will be the minimum of
// len(src) and len(dst).
func copy(dst, src []Type) int

// The delete built-in function deletes the element with the specified key
// (m[key]) from the map. If m is nil or there is no such element, delete
// is a no-op.
func delete(m map[Type]Type1, key Type)

// The len built-in function returns the length of v, according to its type:
//