nb-22 solutions

← Back to lessonChapter 22 / 25 · Advanced II · Worked solution

1. Optional premise, then and now

cause = some repeat_inquirer in RepeatFee: the generated rule carries if some cause as g { when g(subject); }, so without a repeat_inquirer fact the premise is unsatisfied and the rule cannot fire — callback_fee is NEITHER, exactly what fee needs the repeat record asserts. cause = none in FirstNotice: the optional premise vanishes, so inquiry_filed alone suffices and callback_notice is TRUE_ONLY. If you predicted NEITHER for the fee, you read the option correctly; if you predicted FALSE_ONLY, re-read nb-01 — an unsatisfied premise is silence, not a refusal.

2. Surcharge explanation steps

DeskSurcharge/applicable (the generated defeasible rule, named by the self/applicable stable identifier), the insp case assertion (inspects_at), and the open case assertion (desk_open). The waiver defeater DeskSurcharge/excluded/Waiver/excludes does not appear: no waived_case fact is present, so it never fires. A miss here usually means naming the template (inspection) instead of the instance rule.

3. Two cheapest flips

Two solutions — ...#add-i6a and ...#add-i6b — each at cost 1, with "cutoffCost":"1" and two candidates checked. --verify over the two-candidate result reports {"kind":"counterfactual-verification",...,"valid":true} for result id ...#FlipInquiryInput02/result. If you predicted one solution, you assumed the solver breaks ties; it does not — every cheapest patch is listed.

4. Removed spellings

The two migration probes are now rejection cases. Use `relation … kind institutional` for relations and `unless` for exceptions. The earlier LDC-E1328 warning followed by check OK is a historical observation from engine law 0.1.0; neither spelling is accepted by the current compiler.

5. Which edit moves the hash

Re-indenting and the metadata note leave programHash at sha256:cfe2fcb8… — canonicalization ignores byte layout and metadata is outside the semantic preimage. Only the 50 → 51 literal moves it (sha256:8b4127d7…). The stale --verify then fails with COUNTERFACTUAL_PROGRAM_HASH_MISMATCH, exit 1, naming both hashes; a renewed input with the old result fails the second layer instead (COUNTERFACTUAL_CERTIFICATE_INVALID). Re-obtaining the certificate finds add-i6 at cost 1 again and verifies valid:true. If you predicted that any byte change moves the hash, re-read §4 — the hash is semantic, not textual.