Case Expressions

Case Expressions

Gleam does not have if/else statements in the traditional sense. Instead, it uses case expressions for all branching logic:

case value {
  pattern1 -> expression1
  pattern2 -> expression2
  _ -> default_expression
}

Matching on Values

You can match on specific values:

fn describe_day(day: Int) -> String {
  case day {
    1 -> "Monday"
    2 -> "Tuesday"
    3 -> "Wednesday"
    4 -> "Thursday"
    5 -> "Friday"
    6 -> "Saturday"
    7 -> "Sunday"
    _ -> "Unknown"
  }
}

The _ wildcard matches anything and acts as the default case.

Matching on Booleans

Since Gleam has no if/else, you use case with booleans:

let message = case temperature > 30 {
  True -> "It's hot!"
  False -> "It's fine."
}

Case Is an Expression

Every case returns a value, so you can bind the result to a variable:

let grade = case score {
  score if score >= 90 -> "A"
  score if score >= 80 -> "B"
  score if score >= 70 -> "C"
  _ -> "F"
}

Multiple Patterns

You can match multiple values at once using a tuple pattern:

case x, y {
  0, 0 -> "origin"
  0, _ -> "y-axis"
  _, 0 -> "x-axis"
  _, _ -> "elsewhere"
}

Guards

You can add conditions to patterns with if:

case number {
  n if n > 0 -> "positive"
  n if n < 0 -> "negative"
  _ -> "zero"
}

Your Task

Using the recursion concepts from the previous lesson, write a FizzBuzz program.

Write a function called fizzbuzz that takes an Int and returns:

• "FizzBuzz" if divisible by both 3 and 5
• "Fizz" if divisible by 3
• "Buzz" if divisible by 5
• The number as a string otherwise

Use a recursive loop helper to print the result for numbers 1 through 15, each on a separate line.