What I meant to say is that the text for size_t and ptrdiff_t are identical, implying that the underlying types are identical. That is there is logical fallacy.

What I meant to say is that the text for size_t and ptrdiff_t are identical, implying that the underlying types are identical. That is there is logical fallacy. They author states "The type’s size is chosen so that it could store the maximum size of a theoretically possible array of any type" and the same is said for ptrdiff_t, which is quit confusing. Now I realise that in reality they both use 64 bits, it is somewhat strange to use the same text for both.