A small algorithm to find the indexof the first element superior or equal to the given value (in an ordered sequence)

small-algo.scala

#!/bin/sh
exec scala "$0" "$@"
!#

import scala.annotation.tailrec

// ---------------------------------------------------
def searchFirstGreaterOrEqual[T<%Ordered[T]](seq: Seq[T], value: T):Option[Int] = {
    @tailrec
    def binarysearch(left:Int, right:Int):Option[Int] = {
      if (seq(left)>=value) Some(left)
      if (seq(right)<value) None // Not found
      else {
        (left+right)/2 match {
          case m if seq(m)==value => Some(m)
          case m if seq(m)>value  => 
            if (m!=left)  binarysearch(left, m) else Some(m)
          case m if seq(m)<value  => 
            if (m<right) binarysearch(m+1, right)
            else None // Not found 
        }
      }
    }
    binarysearch(0, seq.size-1)
  }
// ---------------------------------------------------


val l1=List(10,20,30,50,100)

def testWith[T<%Ordered[T]](seq:Seq[T], value:T) {
   val result = searchFirstGreaterOrEqual(seq, value)
   println(s"${value}->${result}")
}

println(s"""Results with ${l1.mkString(" ")}""")
testWith(l1, 0)
testWith(l1, 15)
testWith(l1, 20)
testWith(l1, 55)
testWith(l1, 150)