Type mismatch in scala while using eclipse

Question

package week1
import math.abs
object newton {
    def abs(x:Double) = if (x < 0) -x else x

    def sqrtIter(guess: Double, x: Double): Double =
        if (isGoodEnough(guess, x)) guess
        else sqrtIter(improve(guess, x), x)

    def isGoodEnough(guess: Double, x: Double)=
        abs(guess*guess - x  < 0.001)

    def improve(guess: Double, x: Double) =
        (guess + x/guess)/2

    def sqrt (x:Double)= sqrtIter(1.0,x)

}

at line

abs (guess*guess - x <0.001)

eclipse shows the following error

type mismatch; found : Boolean required: Double newton.sc /progfun/src/week1 line 10 Scala Problem

How do I solve this? It's my first time running scala and I'm using the exact code from Functional Programmming class currently going on in Coursera.

Answer 1

This line

abs (guess*guess - x <0.001)

returns a boolean, since it first evaluates guess*guess - x, and than compares it to 0.001.

You should do this

abs (guess*guess - x) < 0.001