nockchain/crates/nockvm/docs/proposal/notes-~2021.9.24.md

Notes ~2021.9.24

Exploration of +mink

The +mink arm in hoon.hoon is a metacircular Nock interpreter intended to be jetted by invoking the host Nock interpreter. In addition to the subject and formula to evaluate, +mink takes a scry gate which is used to evaluate nock 12 (scry) formulas.

The jet uses u3r_mean to take apart the sample of the +mink gate and feeds the resulting nouns to u3n_nock_et, which runs the interpreter and produces a 'toon',

Scry gates are kept in a stack because a scry gate may itself scry, and should not re-enter itself.

Exceptions in new mars

Suboptimal but simple way

The simple thing to do would be to make every continuation expect a toon and on an error or block result, immediately call the next continuation up the stack with it, until a continuation installed e.g. by the +mink jet branched on the result. This is effectively writing the interpreter as a CPS/trampoline translation of +mink.

Likely more optimal way

It should be possible to store exception contexts in the hash table: comprising stack pointers for unwinding, code pointer to jump to (possibly we could use setjmp/longjmp instead), and a hash reference to the next outermost handler. The hash reference to the current exception context would be held in a register. This structure could also hold the current scry gate.