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Loops and Iterations

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In this section, we will explore the various looping constructs available in Scala. Loops are fundamental in programming as they allow us to execute a block of code multiple times. Scala provides several ways to perform iterations, including while loops, do-while loops, and for loops. We will cover each of these in detail, along with practical examples and exercises.

  1. while Loop

The while loop repeatedly executes a block of code as long as a given condition is true.

Syntax

while (condition) {
  // code to be executed
}

Example

var i = 0
while (i < 5) {
  println(s"i = $i")
  i += 1
}

Explanation

  • Initialization: var i = 0 initializes the loop variable.
  • Condition: i < 5 is the condition that is checked before each iteration.
  • Body: println(s"i = $i") and i += 1 are executed as long as the condition is true.

  1. do-while Loop

The do-while loop is similar to the while loop, but it guarantees that the loop body is executed at least once.

Syntax

do {
  // code to be executed
} while (condition)

Example

var j = 0
do {
  println(s"j = $j")
  j += 1
} while (j < 5)

Explanation

  • Initialization: var j = 0 initializes the loop variable.
  • Body: println(s"j = $j") and j += 1 are executed at least once.
  • Condition: j < 5 is checked after each iteration.

  1. for Loop

The for loop in Scala is more powerful and flexible than in many other languages. It can be used for iterating over ranges, collections, and more.

Syntax

for (variable <- range) {
  // code to be executed
}

Example: Iterating Over a Range

for (k <- 1 to 5) {
  println(s"k = $k")
}

Explanation

  • Range: 1 to 5 generates a range from 1 to 5 inclusive.
  • Variable: k takes each value in the range.
  • Body: println(s"k = $k") is executed for each value of k.

Example: Iterating Over a Collection

val fruits = List("Apple", "Banana", "Cherry")
for (fruit <- fruits) {
  println(fruit)
}

Explanation

  • Collection: fruits is a list of strings.
  • Variable: fruit takes each value in the list.
  • Body: println(fruit) is executed for each value of fruit.

  1. Nested Loops

You can nest loops to perform more complex iterations.

Example

for (i <- 1 to 3) {
  for (j <- 1 to 2) {
    println(s"i = $i, j = $j")
  }
}

Explanation

  • Outer Loop: i takes values from 1 to 3.
  • Inner Loop: j takes values from 1 to 2 for each value of i.
  • Body: println(s"i = $i, j = $j") is executed for each combination of i and j.

  1. Practical Exercises

Exercise 1: Sum of First N Natural Numbers

Write a Scala program to calculate the sum of the first N natural numbers using a while loop.

Solution

var n = 10
var sum = 0
var i = 1
while (i <= n) {
  sum += i
  i += 1
}
println(s"Sum of first $n natural numbers is $sum")

Exercise 2: Print Multiplication Table

Write a Scala program to print the multiplication table of a given number using a for loop.

Solution

val number = 5
for (i <- 1 to 10) {
  println(s"$number * $i = ${number * i}")
}

Exercise 3: Find Factorial

Write a Scala program to find the factorial of a given number using a do-while loop.

Solution

var num = 5
var factorial = 1
var i = 1
do {
  factorial *= i
  i += 1
} while (i <= num)
println(s"Factorial of $num is $factorial")

Common Mistakes and Tips

  • Infinite Loops: Ensure that the loop condition will eventually become false to avoid infinite loops.
  • Off-by-One Errors: Be careful with loop boundaries to avoid off-by-one errors.
  • Variable Scope: Declare loop variables with appropriate scope to avoid unintended side effects.

Conclusion

In this section, we covered the different types of loops available in Scala, including while, do-while, and for loops. We also explored nested loops and provided practical exercises to reinforce the concepts. Understanding loops and iterations is crucial for controlling the flow of your programs and performing repetitive tasks efficiently. In the next section, we will delve into functions and methods, which are essential for structuring and organizing your code.

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