Skip to content
@northguild/gmt

A Paired Rest That Does Not Qualify

  • The core functions, which every industry uses.

A Paired Rest That Does Not Qualify

A rule lets two shorter rests count as one full rest when each is at least 2 hours, the longer at least 7 and both together at least 10. A driver rests 6 hours, drives 4, then rests 4. Another rests 7.5, drives 4, then rests 2.5. Which pair counts?

The naive approach

// The naive approach: the two splits everyone remembers
const counts = (a, b) => (a === 7 && b === 3) || (a === 8 && b === 2);
counts(7.5, 2.5); // false — but it meets every floor

// …or only the total
const totalCounts = (a, b) => a + b >= 10;
totalCounts(6, 4); // true — but neither rest is 7 hours

Watch it break

The naive approach silently produces wrong results — there is no GMT equivalent to demonstrate because the failure is not using GMT.

Why

A paired rest is three constraints, not two whole numbers: each rest at least 2 hours, the longer at least 7, the two together at least 10. "7 + 3" and "8 + 2" are only the whole-hour pairs that happen to meet them. 7.5 + 2.5 meets all three; 6 + 4 meets the total and fails "one at least 7". A check written as a list of splits refuses real pairs, and a check of the total accepts false ones. `qualifyingRestPairs` takes the three floors as a `PairSpec` and returns each pair that meets them. A rest that is already a full rest on its own pairs with nothing.

The gmt approach

import { qualifyingRestPairs } from "@northguild/gmt";

const spec = {
statuses: ["off", "sleeper"],
minimum: "PT10H",
pair: { eachAtLeast: "PT2H", oneAtLeast: "PT7H", combinedAtLeast: "PT10H" },
};

qualifyingRestPairs(
[
  { status: "sleeper", start: "2024-01-01T00:00:00Z", end: "2024-01-01T06:00:00Z" },
  { status: "driving", start: "2024-01-01T06:00:00Z", end: "2024-01-01T10:00:00Z" },
  { status: "off", start: "2024-01-01T10:00:00Z", end: "2024-01-01T14:00:00Z" },
],
spec,
); // [] — 6 + 4: neither rest is 7

qualifyingRestPairs(
[
  { status: "sleeper", start: "2024-01-01T00:00:00Z", end: "2024-01-01T07:30:00Z" },
  { status: "driving", start: "2024-01-01T07:30:00Z", end: "2024-01-01T11:30:00Z" },
  { status: "off", start: "2024-01-01T11:30:00Z", end: "2024-01-01T14:00:00Z" },
],
spec,
); // [{ first: { start: "2024-01-01T00:00:00Z", end: "2024-01-01T07:30:00Z" }, second: { start: "2024-01-01T11:30:00Z", end: "2024-01-01T14:00:00Z" } }]

Same widget, working

log
output 

The playground opens on the 7.5 + 2.5 pair. Change the first rest’s end to "2024-01-01T06:00:00Z", and the work entry’s start with it: the pair is 6 + 2.5 now, and the result is []. Lower oneAtLeast to "PT6H" and combinedAtLeast to "PT8H" and the same rests qualify, because the floors are yours. An elapsedWindow rule takes the same PairSpec as exclude, so a qualifying pair moves its close. The rules are in Hours of Work.