def add(that: Rational): Rational =
    new Rational(
        this.numer * that.denom + that.numer * this.denom,
        this.denom * that.denom
    )

def add(that: Int): Rational =
    add(new Rational(that, 1))

def +(that: Rational): Rational =
    new Rational(
        this.numer * that.denom + that.numer * this.denom,
        this.denom * that.denom
    )

def +(that: Int): Rational =
    +(new Rational(that, 1))

(fragment of Rational.scala):19: error: value unary_+ is not a member of this.Rational
+(new Rational(that, 1))
 ^

def +(that: Int): Rational =
  this + (new Rational(that, 1))

def add(that: Int): Rational =
  this add (new Rational(that, 1))

def +(that: Int): Rational = this.+(new Rational(that, 1))

def unary_+: Rational = this.+(new Rational(that, 1))
val a = new Rational(3,2)
val b = +a

def +(that: Int): Rational =
  +(new Rational(that, 1))

def +(that: Int): Rational =
  this +(new Rational(that, 1))