Triangle de Pascal en Scala

// Triangle de pascal :

def pascal(c: Int, r: Int): Int = {

    if ( c > r )
        throw new java.lang.IllegalArgumentException("c > r")
    else if ( c < 0 )
        throw new java.lang.IllegalArgumentException("c < 0")
    else if ( r < 0 )
        throw new java.lang.IllegalArgumentException("r < 0")
    else if ( c==0 || r==c )
        1
    else
        pascal(c, r-1) + pascal(c-1, r-1)

}