Research proof index

On the table of all previously computed values, the step function returns the next one , the obligation Primrec.nat_strong_rec asks for. Four branches, matching ofNat's; the two atomic ones are arithmetic. In the func branch, natToVec succeeding is tested as natToList having the recorded length (natToVec_isSome_of_length/`natToVec_eq_none_of_l...

With every lookup present and non-zero, the fold rebuilds the vecToNat code of the arguments.

getM at Option succeeds exactly when every component does. This is what turns the func branch of ofNat into a statement about each argument separately.