FA-69190 / Tide and marine navigation tables / Member archive

Slack water from current samples: The previous moving sample is only set once · case 05

After the first reversal later slacks are missed or mistimed.

Member previewVariant 5 · 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, 15, 30, 45, 60], [0.5, 0.3, 0.1, -0.2, -0.3]]	`[[23, "ebb-begins"], [30, "ebb-begins"]]`	`[[35, "ebb-begins"]]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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