I use nan boxing in GridWhale. It feels like the Infinite Hotel[1]: you can always add another type. Note that these techniques also rely on the fact that we don't use all 64-bits for memory addressing. If we ever do, lots of VMs will break.

For me, the major advantage of nan boxing is that you don't have to allocate a whole class of types (like floats). That saves so much at garbage collection time.

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[1] https://en.wikipedia.org/wiki/Hilbert%27s_paradox_of_the_Gra...