diff_engine.md

diff engine

Language: Python · Sphere: programming · Category: Io

Signature: () → None

What it does

A simple diff engine for text comparison.

Guarantee

When it runs, diff engine guarantees kinds.count(EditType.EQUAL) == 3; kinds.count(EditType.DELETE) == 3; kinds.count(EditType.INSERT) == 3 (proven by run).

Checkable constraints:

• old_r == old_text.splitlines(keepends=True)
• new_r == new_text.splitlines(keepends=True)
• kinds.count(EditType.EQUAL) == 3
• kinds.count(EditType.DELETE) == 3
• kinds.count(EditType.INSERT) == 3
• all((e.edit_type == EditType.EQUAL for e in same.compute_diff()))
• same.format_unified_diff() == ''
• unified.startswith('@@ -')

Verification evidence

• Green-run: ✓ passes (re-run under the extractor's gate)
• Constraint strength: recovery (truth-pinned)
• Independent oracle: ✓ consensus — xlang (validator v1.9)
• Peer review: unreviewed

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