Convert country code (https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2) to Flag emoji using Kotlin functions.

main.kt

fun countryFlag(code: String) = code
  .uppercase()
  .split("")
  .filter { it.isNotBlank() }
  .map { it.codePointAt(0) + 0x1F1A5 }
  .joinToString("") { String(Character.toChars(it)) }

println(countryFlag("in"))
// output 🇮🇳

Oh you mean there are gaps.

Yes

How did you reach the value of 1F1A5 in the calculation?

For example

Simple alphabet A = 65 = 0x41
Regional indicator symbol 🇦 = 127462 = 0x1F1E6

🇦 - A = 127462 - 65 = 127397 = 0x1F1A5 difference

This is how 2 character country code generated for flag emoji.
Imagine there are only two countries. IN and US. Rest of countries are yet to be allocated.
How would you build logic to validate that? It can be done if someone maintain table for that.

It will require us to build a library for that instead of using simple function to generate flag.

Oh so you reset it to 0, making it the beginning of the range.
Using joinToString means it's multiple Unicode characters. According to the standard, supposed to always be 2 , no?

If so, this shows why the other implementation seems like this instead:

val firstLetter: Int = Character.codePointAt(countryCodeUpperCase, 0) + 0x1F1A5
val secondLetter: Int = Character.codePointAt(countryCodeUpperCase, 1) + 0x1F1A5
return String(Character.toChars(firstLetter)) + String(Character.toChars(secondLetter))

According to the standard, supposed to always be 2 , no?

Right

If so, this shows why the other implementation seems like this instead:

I wanted to do it in Kotlin way 😅

I see. Thanks.
So if I want to check the values, that it is in the range, each of the 2 characters should be between 0x1F1E6 and 0x1F1FF , right?

That's about the output.
The input should just be between A and Z, right (from AA to ZZ)?

each of the 2 characters should be between 0x1F1E6 and 0x1F1FF , right?

Correct

OK thanks