Kotlin utility functions 'safeReadln()' 'String.toIntOrDefault(...)', 'String.toDoubleOrDefault(...)'

kotlin_utils.kt

// package some_kotlin_utils

/**
 * handles the 'end of stream (EOF) case' - e.g. when the user presses "Ctrl-D" instead of typing a string;
 * in this case returns the passed default value (e.g. "") instead of throwing an exception as 'plain' readln() does
 *
 *  @param default String       value returned when exception occurred
 *  @param printErrMsg Boolean  when true prints the message connected with an exception to 'stderr'
 *
 *  @return the user-entered string or the passed default value when an exception occurred
 */
fun safeReadln(default: String = "", printErrMsg: Boolean = false) = try {
    readln().trim()
} catch (e: Exception) {
    if (printErrMsg)
        System.err.println(e)
    default
} // safeReadln(...)


/**
 * example String-extension conversion functions returning some default value instead of 'null' 
 */
fun String.toIntOrDefault(default: Int = Int.MIN_VALUE) = this.toIntOrNull() ?: default
fun String.toLongOrDefault(default: Long = Long.MIN_VALUE) = this.toLongOrNull() ?: default
fun String.toDoubleOrDefault(default: Double = Double.NaN) = this.toDoubleOrNull() ?: default