Get the line and the column of an index in a given CharSequence.

CharSequenceGetLineAndColumn.kt

/**
 * Returns the line and the column of [index] in the given CharSequence.
 */
fun CharSequence.getLineAndColumn(index: Int): LocationInText {
    if (index !in 0..lastIndex) {
        throw IndexOutOfBoundsException(index)
    }
    var lineNumber = 1
    var columnNumber = 1
    forEachIndexed { currentIndex, c ->
        if (index == currentIndex) {
            return LocationInText(
                lineNumber = lineNumber,
                columnNumber = columnNumber
            )
        }
        when (c) {
            '\n' -> {
                lineNumber++
                columnNumber = 1
            }
            else -> columnNumber++
        }
    }
    throw ConcurrentModificationException("The CharSequence has been shrunk concurrently")
}

data class LocationInText(
    val lineNumber: Int,
    val columnNumber: Int
)