passing an array reference to a function in scala

Question

how to pass reference to an array to function in scala.

for example following is a function in c/c++

how to write code for array ref in scala ?

int RMQUtil(int *st, int ss, int se, int qs, int qe, int index)
{
// If segment of this node is a part of given range, then return the
// min of the segment
if (qs <= ss && qe >= se)
    return st[index];

// If segment of this node is outside the given range
if (se < qs || ss > qe)
    return INT_MAX;

// If a part of this segment overlaps with the given range
int mid = getMid(ss, se);
return minVal(RMQUtil(st, ss, mid, qs, qe, 2*index+1),
              RMQUtil(st, mid+1, se, qs, qe, 2*index+2));
}

elm · Accepted Answer · 2014-02-13 14:49:31Z

3

For the multiple arguments of the method consider

case class Params(ss: Int, se: Int, qs: Int, qe: Int, index: Int)

The Scala re-coding for the asked method above,

def RMQUtil(st: Array[Int], p: Params): Int = {
  if (p.qs <= p.ss && p.qe >= p.se) 
    st(index)
  else if (p.se < p.qs || p.ss > p.qe)
    Int.MaxValue
  else {
    val mid: Int = getMid(ss, se)
    Math.min( RMQUtil(st, Params(p.ss, mid, p.qs, p.qe, 2*index+1)),
              RMQUtil(st, Params(mid+1, p.se, p.qs, p.qe, 2*index+2)))
  }
}

edited Feb 13, 2014 at 14:49

answered Feb 13, 2014 at 14:38

elm

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2 Comments

om-nom-nom Over a year ago

Params(p.ss, mid, p.qs, p.qe, 2*index+1) could be p.copy(se = mid, index = 2 * index + 1). This way it easier to grasp what is changed and what is not. Not much win in having parameters passed this way (wrapped in a case class).

elm Over a year ago

@om-nom-nom Thanks for the good observation, indeed not much gain other than utilising the copying method...

serejja · Accepted Answer · 2014-02-13 13:38:37Z

2

Something like this should work:

def RMQUtil(st: Array[Int], ss: Int, se: Int, qs: Int, qe: Int, index: Int): Int = {
  if (qs <= ss && qe >= se)
    return st(index)
  if (se < qs || ss > qe)
    return Int.MaxValue

  val mid = getMid(ss, se) // I assume this is something like (ss + se) / 2
  Math.min(RMQUtil(st, ss, mid, qs, qe, 2*index+1), RMQUtil(st, mid+1, se, qs, qe, 2*index+2))
}

answered Feb 13, 2014 at 13:38

serejja

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1 Comment

serejja Over a year ago

@user2124441 a little comment about your suggested edit - it is not necessary to include the return keyword for the last statement

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