I have this simple function that return some Status:
def getStatus : String =
{
//...
}
And i want to wait until this return specific status but still count this number of calls before exit:
def wait =
{
var count = 0
while (getStatus != "smeStatus" && count < 10) {
// some code here
count++
}
}
How can i avoid of using var ?
You can use a recursive method that takes the count-so-far and returns it + 1:
def waitUntilDone(countSoFar: Int): Int = {
if (getStatus != "smeStatus" && countSoFar < 10) {
// some code here
waitUntilDone(countSoFar + 1)
} else {
countSoFar
}
}
// invoke it starting with 0:
val count = waitUntilDone(0)
def status = ""
def waiting: Unit = {
def check(count: Int): Unit = {
if(count < 10 && status != "smeStatus") {
// do something
check(count + 1)
}
}
check(0)
}
Related
I have following code :-
var ArrayStop = new ArrayList[imeistoppage]()
val listings = rddStopCalculate.zipWithIndex().map(p => {
if (p._2 == 0) {
imei = p._1.imei
lat = p._1.latitude
long = p._1.longitude
gpsdt = p._1.gpsdt
} else if (p._2 > 0 && p._2 != lastindex) {
if (p._1.imei.equals(imei) && p._1.latitude == lat && p._1.longitude == long) {
flag += 1
newgpsdt = p._1.gpsdt
} else {
if (flag > 0) {
timeDiff = newgpsdt.getTime() - gpsdt.getTime()
if (timeDiff > 60000) {
ArrayStop.add(imeistoppage(p._1.imei, lat, long, timeDiff))
}
flag = 0
}
imei = p._1.imei
lat = p._1.latitude
long = p._1.longitude
gpsdt = p._1.gpsdt
}
} else {
if (p._1.imei.equals(imei) && p._1.latitude == lat && p._1.longitude == long) {
flag += 1
newgpsdt = p._1.gpsdt
}
if (flag > 0) {
timeDiff = newgpsdt.getTime() - gpsdt.getTime()
if (timeDiff > 60000) {
ArrayStop.add(imeistoppage(p._1.imei, lat, long, timeDiff))
}
flag = 0
}
}
ArrayStop
}).collect()
val returnList = listings(listings.length - 1)
val tempCollection = returnList.asScala
val tempRDD = sc.parallelize(tempCollection)
tempRDD.saveToCassandra("db", "table", SomeColumns("imei", "lat", "long", "duration"))
As we can see in above code I'm actually adding data to ArrayStop for specific IF condition only and I want this to be accessed outside this rdd loop but I was unable to do so So I created a variable "listings" to store data which is actually taking all the rows whereas I want only those entries which are added in ArrayStop. So what is the best way to bring any array outside nested If-else block. This is different from this issue
Scala spark, listbuffer is empty
Thanks,
I am builing a little method for parenthesis balancing using scala and recursion.
I came out this code which surprisingly doesn't work.
object Test{
def balance(chars: List[Char]): Boolean=
{
var opening_index: Int = -1
var closing_index: Int = -1
opening_index = chars.indexOf('(')
closing_index = chars.indexOf(')')
println(opening_index)
println(closing_index)
if ( chars.size == 0 ) true
if ((opening_index == -1) & (closing_index== -1))
{
true
}
if (closing_index> -1 & opening_index> -1)
{
if (closing_index< opening_index) return(false)
else
{
balance(chars.filter(_!=chars(closing_index)).filter(_!=chars(opening_index)))
}
}
else
return (false)
}
val lst:List[Char] = List('(',')' ,'3','4')
balance(lst)
}
I am aware that there are other similar posts but I am more interested in using this approach than the other ones.
You probably wanted to filter by index, not by character. As it is, your code erases all parentheses in the first round.
This here works with zipWithIndex, and compares the index with opening_index and closing_index:
def balance(chars: List[Char]): Boolean = {
val opening_index = chars.indexOf('(')
val closing_index = chars.indexOf(')')
if ( chars.size == 0 ) {
true
} else if ((opening_index == -1) && (closing_index== -1)) {
true
} else if (closing_index > -1 && opening_index > -1) {
if (closing_index < opening_index) {
false
} else {
balance(
chars.zipWithIndex.filterNot{
case (c, i) => i == opening_index || i == closing_index
}.map(_._1)
)
}
} else {
false
}
}
println(balance("()34".toList))
println(balance("()34)".toList))
println(balance("(x)(y(z))".toList))
println(balance("(x)(y(z)".toList))
Output:
true
false
true
false
You can use below solution to check balance parenthesis.
object Driver extends App{
def balance(chars: List[Char]): Boolean=
{
if (chars.mkString("").length() == 0) {
return true;
}
if (chars.mkString("").contains("()")) {
return balance(chars.mkString("").replaceFirst("\\(\\)", "").toCharArray.toList);
}
if (chars.mkString("").contains("[]")) {
return balance(chars.mkString("").replaceFirst("\\[\\]", "").toCharArray.toList);
}
if (chars.mkString("").contains("{}")) {
return balance(chars.mkString("").replaceFirst("\\{\\}", "").toCharArray.toList);
} else {
return false;
}
}
println(balance(List('(','{','}')))
println(balance(List('(','{','}',')')))
}
There are two main (functional) problems with this code.
Firstly, this test does nothing because the result is thrown away
if ((opening_index == -1) & (closing_index== -1))
{
true
}
You probably meant return true
Secondly, the recursive call is wrong
balance(chars.filter(_ != chars(closing_index)).filter(_ != chars(opening_index)))
These two calls to filter are removing all the parentheses from the list, so the call to balance will always succeed even if the rest of the list is unbalanced.
You probably want to use three slice calls to remove the specific parentheses at opening_index and closing_index.
I don't know how convert java "continue" to scala.
I can use marker from bool + break, but its bad idea
Google did not help :(
It's my first program in scala... yep.. it's horrible
sort java
def sort(in: Array[Int], a:Int, b:Int)
{
var i,j,mode;
double sr=0;
if (a>=b) return; // size =0
for (i=a; i<=b; i++) sr+=in[i];
sr=sr/(b-a+1);
for (i=a, j=b; i <= j;)
{
if (in[i]< sr) { i++; continue; } // left > continue
if (in[j]>=sr) { j--; continue; } // right, continue
int c = in[i]; in[i] = in[j]; in[j]=c;
i++,j--; // swap and continue
}
if (i==a) return;
sort(in,a,j); sort(in,i,b);
}
sort scala...
def SortMerger(in:List[Int], a:Int, b:Int):Unit = {
var i = 0;
var j = 0;
var mode = 0;
var sr = 0.0;
if(a>=b) return;
i=a
while(i<=b)
{
sr+=in.ElementOf(i);
i += 1
}
sr=sr/(b-a+1)
i=a
j=b
while(i<=j)
{
if(in.ElementOf(i)<sr) {
i += 1;
// where continue??? ><
}
}
return
}
Scala has no continue statement, but what you are trying to do can be done with a simple if/else structure.
while(i<=j)
{
if(in(i) < sr) {
i += 1
} else if (in(j) >= sr) {
j -= 1
} else {
int c = in(i)
in(i) = in(j)
in(j) = c
i += 1
j -= 1
}
}
Note that the type of in here should be Array, not List
Why does the following code return a empty list instead of a list with the values at odd positions ?
def f(arr:List[Int]) : List[Int] = {
def odd_concat(list_odd:List[Int], arr_index:Int) : List[Int] = {
if(arr_index == arr.size) {
list_odd
}
else if(arr_index % 2 == 0) {
odd_concat(list_odd, arr_index + 1)
}
else {
//println(arr(arr_index))
list_odd:+arr(arr_index)
odd_concat(list_odd, arr_index + 1)
}
}
odd_concat(List(), 0)
}
You are using immutable list, immutable means the object cannot be change.
Your code:
list_odd:+arr(arr_index)
It does not change the list_odd with the value of arr(arr_index) rather give a new instance of List with values added.
Try to insert that code inside the odd_concat() instead, like the following:
def f(arr:List[Int]) : List[Int] = {
def odd_concat(list_odd:List[Int], arr_index:Int) : List[Int] = {
if(arr_index == arr.size) {
list_odd
}
else if(arr_index % 2 == 0) {
odd_concat(list_odd, arr_index + 1)
}
else {
//println(arr(arr_index))
odd_concat(list_odd:+arr(arr_index), arr_index + 1)
}
}
odd_concat(List(), 0)
}
I have to make a connect-four game using scala. I have attached the code but everytime the game runs and gets to row 3 it just continues to change the second rows entry instead of going to the next row. Any help would be appreciated. I found this code on another thread on here and couldn't figure out how to get it to work:
// makes the board
val table = Array.fill(9,8)('-')
var i = 0;
while(i < 8){
table(8)(i) = (i+'0').toChar
i = i+1;
}
// prints starting board
def printBoard(table: Array[Array[Char]]) {
table.foreach( x => println(x.mkString(" ")))
}
//player 1 moves
def playerMove1(){
val move = readInt
var currentRow1 = 7
while (currentRow1 >= 0)
if (table(currentRow1)(move) != ('-')) {
currentRow1 = (currentRow1-1)
table(currentRow1)(move) = ('X')
return (player2)}
} else {
table(currentRow1)(move) = ('X')
return (player2)
}
}
//player 2 moves
def playerMove2(){
val move = readInt
var currentRow2 = 7
while (currentRow2 >= 0)
if (table(currentRow2)(move) != ('-')) {
currentRow2 = (currentRow2-1)
table(currentRow2)(move) = ('O')
return (player1)}
} else {
table(currentRow2)(move) = ('O')
return (player1)
}
}
//player 1
def player1(){
printBoard(table)
println("Player 1 it is your turn. Choose a column 0-7")
playerMove1()
}
//player 2
def player2(){
printBoard(table)
println("Player 2 it is your turn. Choose a column 0-7")
playerMove2()
}
for (turn <- 1 to 32){
player1
player2
}
I've tried to make your code readable and compiling and also tried to fix some logic.
However, I've never worked with Scala so this is just a first sketch where you might want to continue ...
Some functions can be merged and the currentRow needed a fix. See here:
object ConnectFour{
val table = Array.fill(9,8)('-')
val currentRow = Array.fill(8)(8)
def main(args: Array[String]) {
var i = 0;
while(i < 8) {
table(8)(i) = (i+'0').toChar
i = i+1;
}
player(1)
}
def printBoard(table: Array[Array[Char]]) {
table.foreach( x => println(x.mkString(" ")))
}
def player(playerNr : Int){
printBoard(table)
println("Player " + playerNr + " it is your turn. Choose a column 0-7")
var column = readAndVerifyInt
var nextUser = 1 : Int
var symbol = 'O' : Char
if(playerNr == 1) {
symbol = 'X'
nextUser = 2
}
var curR = currentRow(column)
while (curR >= 0) {
if (table(curR)(column) != ('-')) {
curR = curR-1
currentRow(column) = curR
}
table(curR)(column) = symbol
player(nextUser)
}
}
def readAndVerifyInt() : Int = {
var column = readInt
if (column >= 0 && column <= 7) {
return column
} else {
println(" > Please try again")
return readAndVerifyInt
}
}
}