map

Map Exercise

What is a Map?

A map, also known as an associative array or dictionary, is a built-in Go data type that stores key-value pairs. It allows you to look up values by their corresponding keys.

Think of a map like a phonebook. You have names (keys) and phone numbers (values). When you want to find someone's phone number, you look them up in the phonebook using their name as the key.

How does it work? (simplified)

1. Keys: Each entry in a map has a unique key. Keys are used to identify and retrieve values from the map.
2. Values: Each key is associated with a value. Values can be any type of data (e.g., strings, integers, structs).
3. Lookups: When you want to find a value, you use its corresponding key to look it up in the map.

Real-world Example

Let's say we're building an online shopping cart application. We need to store information about each product, such as its name, price, and quantity. A map is perfect for this because we can use the product ID (a unique string) as the key and store the corresponding product information as the value.

example:

m := make(map[string]string)

// Add some entries to the map
m["foo"] = "Lorem ipsum dolor sit amet"
// -> map[string]string{"foo":"Lorem ipsum dolor sit amet"}

m["bar"] = "consetetur sadipscing elitr"
// -> map[string]string{"foo":"Lorem ipsum dolor sit amet", "bar":"consetetur sadipscing elitr"}

m["baz"] = "sed diam nonumy eirmod tempor" 
// -> map[string]string{"foo":"Lorem ipsum dolor sit amet", "bar":"consetetur sadipscing elitr", "baz":"sed diam nonumy eirmod tempor"}

In this example, we use the keys "foo", "bar", and "baz" to store the corresponding text values. We can then look up the value for a given key using m[key].

For example:

fmt.Println(m["foo"]) // Output: Lorem ipsum dolor sit amet

Hands-on Practice

In this exercise, you'll practice working with maps in Go. Open the map.go file and complete the exercises.

Replace each occurrence of panic("implement-me") with a proper implementation.

Then, run go test to verify your work using the tests in map_test.go.