Scala how to split string and store into array?

Question

I am currently writing a program that read a string like "2 + 2". It should be split regarding the spaces and store into an Array like Array(2, +, 2). However, I am not sure how to do it within a method (since I usually work in Scala interpreter), access to the result after I split it. I know that in java, you can do String[] arr = string.split("\s+").

def eval(s: String): Double = {
var result = 0;
s.split("\\s+");
//how do i retrieve the element that was split?
// I am trying to retrieve, like the above example, the 2 and 2
// perform an addition on them so the method will return a double
result;
}

so what's your problem exactly? since s.split("\\s+"); should work in Scala!? Just assign it to a variable or whatever you wanna do and read the array elements: val arr = s.split("\\s+"); — xander
– xander, Commented Feb 28, 2017 at 7:59

Community · Accepted Answer · 2017-05-23 11:46:13Z

1

Splitting is same as in java, you can read the answers here.

Only thing you are missing is accessing the array which is done with array(index)

def eval(s: String): Double = {
  val operands = s.split("\\s+")
  operands(0).toDouble + operands(2).toDouble //the last statement is return statement
}

assert(eval("2 + 2") == 4)

The above will always do addition even if you do eval("2 - 2") == 4

But if you want to have all operations(+, -) then do pattern match on your operator which is index 1.

def eval(s: String): Double = {
  val operandsWithOperator = s.split("\\s+")

  operandsWithOperator(1) match {
    case "+" => operandsWithOperator(0).toDouble + operandsWithOperator(2).toDouble
    case "-" => operandsWithOperator(0).toDouble - operandsWithOperator(2).toDouble
    case "*" => operandsWithOperator(0).toDouble * operandsWithOperator(2).toDouble
    case "/" => operandsWithOperator(0).toDouble / operandsWithOperator(2).toDouble
  }
}

assert(eval("2 + 2") == 4)
assert(eval("2 - 2") == 0)
assert(eval("2 * 3") == 6)
assert(eval("2 / 2") == 1)

And if you want more than two operands, then recurse.

edited May 23, 2017 at 11:46

CommunityBot

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answered Feb 28, 2017 at 8:16

prayagupadhyay

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2 Comments

jwvh Over a year ago

Don't need the result var. Just conclude with the match statement.

user21478621 Over a year ago

tyvm! This is very helpful :>

echo · Accepted Answer · 2017-02-28 08:48:03Z

0

Use pattern matching to extract the string items and also to match the operator,

def eval(s: String): Double = {
  val Array(left, op, right, _*) = s.split("\\s+")
  (left.toDouble, op, right.toDouble) match {
    case (a, "+", b) => a+b
    case _           => Double.NaN  // error value
  }
}

answered Feb 28, 2017 at 8:48

echo

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