hakorune/docs/development/current/main/design/pattern6-7-contracts.md

Pattern6/7 Contracts (SSOT)

This document defines the contract boundary for Pattern6/7 extractors. It is the SSOT for NotApplicable vs Freeze decisions.

Common Rule

• NotApplicable: shape mismatch (another pattern may apply)
• Freeze: shape matches but contract is violated (fail-fast)

Tags:

• Pattern6: [joinir/phase29ab/pattern6/contract]
• Pattern7: [joinir/phase29ab/pattern7/contract]

Pattern6 (ScanWithInit / MatchScan)

Accepted shape:

• loop(i < s.length()) or loop(i <= s.length() - needle.length())
• if s.substring(i, i + 1) == needle { return i }
• step update exists and matches direction

Freeze conditions:

• step update missing
• forward scan with step != i = i + 1
• reverse scan with step != i = i - 1 Note:
• plan line supports reverse scan (cond: i >= 0, step: i = i - 1)

Pattern7 (SplitScan)

Accepted shape:

• loop(i <= s.length() - separator.length())
• if s.substring(i, i + separator.length()) == separator
• then: result.push(...), start = i + separator.length(), i = start
• else: i = i + 1

Freeze conditions:

• then/else update contracts broken (start/i updates)
• separator literal length != 1 (P0 scope)

Fixtures (OK vs Contract)

Pattern6 OK:

• apps/tests/phase29ab_pattern6_scan_with_init_ok_min.hako
• apps/tests/phase29ab_pattern6_reverse_ok_min.hako
• apps/tests/phase29ab_pattern6_matchscan_ok_min.hako

Pattern6 contract:

• apps/tests/phase29ab_pattern6_firstfail_min.hako
• apps/tests/phase29ab_pattern6_reverse_firstfail_min.hako
• apps/tests/phase29ab_pattern6_matchscan_firstfail_min.hako

Pattern7 OK:

• apps/tests/phase29ab_pattern7_splitscan_ok_min.hako
• apps/tests/phase29ac_pattern7_splitscan_nearmiss_fix_ok_min.hako

Pattern7 contract:

• apps/tests/phase29ab_pattern7_firstfail_min.hako