instructions.md

A friend of you has an old wholesale store called Gross Store, the name came from the quantity of the item that the store sell, it's all in gross unit. Your friend asked you to implement a point of sale (POS) system for his store, but first, you want to build a prototype for it, in your prototype, your system will only record the quantity. Your friend gave you a list of measurements to help you:

Unit	Score
quarter_of_a_dozen	3
half_of_a_dozen	6
dozen	12
small_gross	120
gross	144
great_gross	1728

1. Store the unit of measurement in your program

In order to use the measurement, you need to store the measurement in your program.

units := Units()
fmt.Println(units)
// Output: map[...]

2. Create a new customer bill

You need to implement a function that create a new bill for the customer.

bill := NewBill()
fmt.Println(bill)
// Output: map[]

3. Add item to the customer bill

To implement this, you'll need to:

• Check whether the given unit of measurement is correct
• Add the item to the customer bill, indexed by the item name. You probably also need a variable to represent the customer bill, you are expected to use map

bill := NewBill()
ok := AddItem(bill, "carrot", "dozen")
fmt.Println(ok)
// Output: true or false

Note that the returned value is type of bool

4. Remove item from the customer bill

To implement this, you'll need to:

• Check whether the given item is in the bill
• Check whether the given unit of measurement is correct
• Check whether the new quantity is less than 0, is so return false
• Check whether the new quantity is 0, is so return remove the item from the customer bill
• Otherwise reduce the quantity of the item

bill := NewBill()
ok := RemoveItem(bill, "carrot", "dozen")
fmt.Println(ok)
// Output: true or false

Note that the returned value is type of bool

5. Return the number of specific item that is in the customer bill

To implement this, you'll need to:

• Check whether the given item is in the bill
• Otherwise, return the quantity of the item

bill := NewBill()
qty, ok := GetItem(bill, "carrot")
fmt.Println(qty)
// Output: 12
fmt.Println(ok)
// Output: true or false

Note that the returned value are types of int and bool Note that there's no value returned by this function