Is there a more concise way of doing the following...

# announcements

[therealbluepandabear]

Is there a more concise way of doing the following:

fun charToNumber(input: Char): Int {
    val numbersToLetters = listOf('A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S',
    'T', 'U', 'V', 'W', 'X', 'Y', 'Z')

    return numbersToLetters.indexOf(input.toUpperCase()) + 1
}

[ephemient]

('A'..'Z').indexOf(input.toUpperCase())

[rnett]

'A'.toInt() - 64 (for 1 indexed) See http://www.asciitable.com/

[ephemient]

yes, Kotlin can optimize out some usages of constant ranges but this isn't one of them, CharRange.indexOf() results in a linear scan like Tom's original code

[ephemient]

it'll be a little more complex to map non-letters to -1, but not by much

[ephemient]

something simple could be

when (input) {
    'A'..'Z' -> input.toInt() - 'A'.toInt()
    'a'..'z' -> input.toInt() - 'a'.toInt()
    else -> -1
}

[ilya.gorbunov]

To add to the above snippet ⬆️, toInt conversion is not necessary, just input - 'A' will do.

[ephemient]

oh I didn't realize the overloads were such that Char - Char = Int and Char - Int = Char. just checked now, yes that works the right way right out of the box