40 lines
1.2 KiB
Markdown
40 lines
1.2 KiB
Markdown
# Pattern6/7 Contracts (SSOT)
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This document defines the **contract boundary** for Pattern6/7 extractors.
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It is the SSOT for `NotApplicable` vs `Freeze` decisions.
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## Common Rule
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- **NotApplicable**: shape mismatch (another pattern may apply)
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- **Freeze**: shape matches but contract is violated (fail-fast)
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Tags:
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- Pattern6: `[joinir/phase29ab/pattern6/contract]`
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- Pattern7: `[joinir/phase29ab/pattern7/contract]`
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## Pattern6 (ScanWithInit / MatchScan)
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Accepted shape:
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- `loop(i < s.length())` or `loop(i <= s.length() - needle.length())`
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- `if s.substring(i, i + 1) == needle { return i }`
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- step update exists and matches direction
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Freeze conditions:
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- step update missing
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- forward scan with step != `i = i + 1`
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- reverse scan with step != `i = i - 1`
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Note:
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- plan line is forward-only; reverse scans are currently treated as NotApplicable
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## Pattern7 (SplitScan)
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Accepted shape:
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- `loop(i <= s.length() - separator.length())`
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- `if s.substring(i, i + separator.length()) == separator`
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- then: `result.push(...)`, `start = i + separator.length()`, `i = start`
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- else: `i = i + 1`
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Freeze conditions:
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- then/else update contracts broken (start/i updates)
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- separator literal length != 1 (P0 scope)
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