Fold and reduce operations in Kotlin - Mini Project: Build & Apply

Fold and reduce operations

📖 Scenario: You are working with a list of daily sales amounts in a small shop. You want to find the total sales and the highest single sale using Kotlin's fold and reduce operations.

🎯 Goal: Build a Kotlin program that uses fold to calculate the total sales and reduce to find the highest sale from a list of daily sales.

📋 What You'll Learn

Create a list of daily sales amounts with exact values

Create an initial value variable for fold operation

Use fold to calculate total sales

Use reduce to find the highest sale

Print the total sales and highest sale exactly as specified

💡 Why This Matters

🌍 Real World

Calculating total sales and highest sale is common in retail and business to understand performance.

💼 Career

Knowing fold and reduce helps in data processing tasks, common in software development and data analysis roles.

1

Create the sales data list

Create a list called dailySales with these exact values: 150, 200, 50, 400, 100

Kotlin

# Create the list dailySales with the exact values
# Your code here

Need a hint?

Use listOf to create the list with the exact numbers.

2

Create initial value for fold

Create an integer variable called initialTotal and set it to 0 to use as the starting value for the fold operation.

Kotlin

val dailySales = listOf(150, 200, 50, 400, 100)
# Create initialTotal and set it to 0
# Your code here

Need a hint?

Just create a variable with the exact name and value.

3

Calculate total sales with fold and find highest sale with reduce

Use fold on dailySales with initialTotal to calculate the total sales and store it in totalSales. Then use reduce on dailySales to find the highest sale and store it in highestSale.

Kotlin

val dailySales = listOf(150, 200, 50, 400, 100)
val initialTotal = 0
# Use fold to calculate totalSales
# Use reduce to find highestSale
# Your code here

Need a hint?

Use fold with an accumulator adding each sale, and reduce with a comparison to find the max.

4

Print the results

Print the total sales using println("Total sales: $totalSales") and print the highest sale using println("Highest sale: $highestSale").

Kotlin

val dailySales = listOf(150, 200, 50, 400, 100)
val initialTotal = 0
val totalSales = dailySales.fold(initialTotal) { acc, sale -> acc + sale }
val highestSale = dailySales.reduce { acc, sale -> if (sale > acc) sale else acc }
# Print totalSales and highestSale
# Your code here

Need a hint?

Use println exactly as shown to print the results.