Fix ACTZipper::val_count counting from the zipper root, not the focus - #80
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Fix ACTZipper::val_count counting from the zipper root, not the focus#80imlvts wants to merge 1 commit into
imlvts wants to merge 1 commit into
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`val_count` opened with `zipper.reset()`. `ZipperValues::val_count` counts the values at and below the *focus*, so this returned the count for the whole subtrie under the zipper's root wherever the focus was, and was right only when the focus happened to be at the root. Removing the reset is not quite enough: `to_next_val` walks the zipper's entire subtrie rather than the part below the focus, so the walk has to stop when it leaves. Depth-first order visits everything below the focus before anything outside it, so the first path that no longer starts with the focus ends the count. Regression test: `act_zipper_val_count_counts_from_the_focus`, against the PathMap zipper at six foci from the map root and three from a zipper rooted below it. Fails before this change. lean/FINDINGS.md ACT finding "val_count_ignores_focus" on the lean-fuzzer-restage branch. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01BZmoASqM5FUuzvJeJaYQjR
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val_countopened withzipper.reset().ZipperValues::val_countcounts the values at and below the focus, so this returned the count for the whole subtrie under the zipper's root wherever the focus was, and was right only when the focus happened to be at the root.Removing the reset is not quite enough:
to_next_valwalks the zipper's entire subtrie rather than the part below the focus, so the walk has to stop when it leaves. Depth-first order visits everything below the focus before anything outside it, so the first path that no longer starts with the focus ends the count.Regression test:
act_zipper_val_count_counts_from_the_focus, against the PathMap zipper at six foci from the map root and three from a zipper rooted below it. Fails before this change.lean/FINDINGS.md ACT finding "val_count_ignores_focus" on the lean-fuzzer-restage branch.