i've been thinking about null pointers

A thought experiment exploring the conceptual oddity of null pointers — specifically that null is a single non-address value embedded in a pointer type to carry semantic meaning. The author extends this idea: since many pointer values in 64-bit userspace are inherently invalid addresses, why not use multiple impossible pointer values to encode richer type information? Using Hare's tagged union return types as an example, the author sketches how sentinel pointer values (like 0x1 for EOF) could eliminate the need for a tag field, fitting more information into fewer registers. The concept is compared to NaN boxing but applied to pointers.

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