一个矩阵的简单运算工具类

object MatrixTool extends App {

class Matrix(val m: Array[Array[Double]]) {
val rows = m.length
val cols = m(0).length

def apply(r: Int, c: Int) = m(r)(c)

def update(r: Int, c: Int, v: Double): Unit = {
m(r)(c) = v
}

private def compute(that: Matrix, f: (Double, Double) => Double): Array[Array[Double]] = {
if (that.dim != dim) throw new Exception("can only add matrix with same size")
(for (i <- m.indices) yield m(i).zip(that.m(i)).map(v => f(v._1, v._2))).toArray
}

def dim = (rows, cols)

def *(s: Double) = {
new Matrix(
(for (i <- m.indices) yield m(i).map(_ * s)).toArray
)
}

def +(that: Matrix) = new Matrix(compute(that, (a, b) => a + b))

def *(that: Matrix) = new Matrix(compute(that, (a, b) => a * b))

override def toString = m.map(_.mkString(" ")).mkString("\n")
}

val m = new Matrix(Array(Array(1.0, 2.0, 3.0), Array(4.0, 5.0, 6.0)))
val n = new Matrix(Array(Array(1.0, 2.0, 3.0), Array(4.0, 5.0, 6.0)))
println(m)
println(n)
println((m * 2 + n) * m)
}