Level 22. Maybe: Something or Nothing

Sometimes a value might exist, or it might not. Like looking for your keys — they’re either in your pocket, or they’re not!

Hica has a special type called maybe for this. A maybe value is either:

• Some(value) — “yes, here it is!”
• None — “nope, nothing here”

Creating maybe values

let found = Some(42)    // We found the answer!
let lost = None         // Nothing here

Looking inside with match

To find out what’s inside a maybe, use match:

fun describe(x) => match x {
  Some(n) => "found: {n}",
  None    => "nothing"
}

fun main() {
  println(describe(Some(42)))  // "found: 42"
  println(describe(None))      // "nothing"
}

Think of Some like an envelope with a letter inside, and None like an empty envelope. The match opens the envelope to check.

When is maybe useful?

Maybe is great when something might not have an answer:

• Looking up a word in a dictionary, maybe it’s there, maybe it’s not
• Finding the first even number in a list, maybe there is one, maybe not
• Getting input from a user, maybe they typed something, maybe they didn’t

fun first_positive(nums) => match nums {
  [] => None,
  _  => Some(nums[0])
}

fun main() {
  println(first_positive([10, 20]))
  println(first_positive([]))
}

🎯 Try it: Write a function that takes a number and returns Some("even") if it’s even, or None if it’s odd.

Helpers: working with maybe without match

Sometimes you don’t want to write a whole match just to peek inside. Hica has helper functions (called combinators) that work like little machines you can pipe through:

// Transform what's inside (if anything)
let doubled = Some(5) |> map_maybe((x) => x * 2)
println(doubled)   // Some(10)

// Get the value or use a backup
let value = None |> unwrap_maybe_or(0)
println(value)     // 0

// Ask yes/no questions
println(is_some(Some(1)))   // true
println(is_none(None))      // true

Think of map_maybe like putting a letter through a stamping machine. If the envelope is empty (None), the machine does nothing. If there’s a letter inside (Some), it stamps it and puts it back.