FA-69183 / Tide and marine navigation tables / Member archive

Slack water from current samples: Slack labels name the stream that ends · case 03

Flood-begins and ebb-begins are swapped in the tide table.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

Input [ts, vs]: sample times (minutes) and signed current (flood positive). Zero samples are skipped; a slack occurs between consecutive nonzero samples of opposite sign. With no zero samples in between, slack time is linearly interpolated; across a run of zero samples it is the midpoint of the zero run. Times round half up to minutes; the label says which stream begins. Return [[minute, "flood-begins"|"ebb-begins"], ...].

Why this case matters

Tide tables and passage plans turn published predictions into go/no-go decisions about depth, clearance and timing.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
slack water from current samples [[0, 20, 40, 60, 80, 100, 120], [2.0, 1.0, -1.0, -2.0, -0.5, 0.5, 1.5]]	`[[30, "flood-begins"], [90, "ebb-begins"]]`	`[[30, "ebb-begins"], [90, "flood-begins"]]`	Failed

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