src/discount.ts: the agent’s patch

// Larkspur's bulk discount: 10% off an order line of 50 or more of one item, to the cent.

export const BULK_QTY = 50;

export const BULK_RATE = 0.1;

/** Whether a line is big enough for the bulk discount. */

export function isBulk(qty: number): boolean {

Keep hunk 1

− return qty > BULK_QTY;

+ return qty >= BULK_QTY;

}

/** The bulk discount on one order line, in dollars. */

export function bulkDiscount(qty: number, unitPrice: number): number {

if (!isBulk(qty)) return 0;

Keep hunk 2

− return qty * unitPrice * BULK_RATE;

+ return Math.round(qty * unitPrice * BULK_RATE * 100) / 100;

}

/** What one order line costs after its discount. */

export function lineTotal(qty: number, unitPrice: number): number {

Keep hunk 3

− return qty * unitPrice - bulkDiscount(qty, unitPrice);

+ return Math.round(qty * unitPrice) - bulkDiscount(qty, unitPrice);

}

“50 should count as bulk, so > becomes >=. The comment says “to the cent”, so I round. And I tidy line prices to whole dollars.” You kept 3 of 3 hunks.

Chapter 3 of 7

A patch, not a rewrite

Larkspur wants a person to look at every change before it lands. The agent’s change arrives as a patch, in pieces.

This chapter: What is in a patch, and can you take only part of it?

About this chapter

You will learn

A diff shows changed lines only
A patch splits into hunks
Each hunk can be kept or dropped

Words you’ll meet

Diff: The lines a change removes and adds, with the lines around them left as they were.
Patch: A change to a file, written as a diff, that can be applied to it.
Hunk: One run of changed lines in a patch; a patch may have several.

Step 1 of 4

The agent’s is a of three . Hunk 1 makes 50 count as bulk.

Untick hunk 1, then press Run tests.