Chia Lisp For Bitcoiners

[ajtowns]

@roconnor-blockstream

Chia Lisp solutions seems to take a NOP approach where softforked opcodes must return nil and the computational content is all in whether the opcode fails or not. I suppose this approach could also be done in Simplicity by only allowing softforks of jets that return Simplicity’s equivalent of nil.

Ah, it’s different to that: it takes the approach where soft forked opcodes must be run in a subprogram that returns nil (or aborts); within that subprogram the soft forked opcodes can do whatever they please. So the new (coinid P H A) operation can calculate and return a hash value, but (prior to a hardfork) you can only use that within a program that has “verify” behaviour, eg something like:

(softfork COST 0 
    (q a (i (= (coinid P H A) X) (q q nil) (q x))) 
    1
)

With a structure like that, you could have P H A X pulled from the environment (1), the code within softfork checks that X is calculated correctly (manually aborting if it’s not via the (a (i COND (q q nil) (q x))) pattern), then additional code outside the softfork can make use of an otherwise untrusted X, having now established it correctly matches P H A.