MyNote/Scala at master · roliygu/MyNote · GitHub

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console
scala> 34+65
res0: Int = 99

scala> def radius = 10
radius: Int

scala> def pi = 3.14159
pi: Double

scala> radius * pi
res1: Double = 31.4159

scala> def square(x:Double) = x * x
square: (x:Double)Double

scala> square(2)
res2: Double = 4.0

scala> square(5+4)
res3: Double = 81.0

scala> square(square(4))
res4: Double = 256.0

scala> def sumOfSquares(x: Double,y: Double) = square(x) + square(y)
sumOfSquares: (x: Double,y:Doble)Double


/*
def power(x: Double,y Int)[: Double (返回类型，可以省略)]= ...
int 32-bit     double 64-bit
*/

scala> def abs(x: Int) = if (x>=0) x else -x
abs:(x: Int)Int

scala> abs(-10)
res5: Int = 10

/*
布尔操作：
ture false
!b
b && b
b || b
e <= e,e >= e,e < e,e > e,e == e,e != e
!ture ---- false
!false ---- true
true && e(e是任意变量) ---- e
false && e ---- false
true || e ---- true
false || e ---- e
*/

scala> def and(x: Boolean,y: => Boolean)=
	|	if(x) y else false
and: (x: Boolean, y: => Boolean)Boolean


def sqrtIter(guess: Double, x: Double): Double =
	if (isGoodEough(guess,x)) guess
	else sqrtIter(improve(guess,x),x)         //> sqrtIter: (guess: Double, x: Double)Double

def isGoodEough(guess: Double, x: Double) =
	abs(guess * guess -x) / x < 0.001         //> isGoodEough: (guess: Double, x: Double)Boolean

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

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


def sum(f: Int=>Int,a: Int,b: Int)={
	def loop(a:Int,acc:Int):Int =
		if(a>b)acc
		else loop(a+1,f(a)+acc)
	loop(a,0)
}
//////////////////////////////////////////////////////////////////////////////////////
object rationls {
  val x = new Rational(1,3)                       //> x  : weekthree.Rational = 1/3
  val y = new Rational(5,7)                       //> y  : weekthree.Rational = 5/7
  val z = new Rational(3,2)                       //> z  : weekthree.Rational = 3/2
  x.numer                                         //> res0: Int = 1
  x.denom                                         //> res1: Int = 3
  x.neg                                           //> res2: weekthree.Rational = -1/3
  x.sub(y).sub(z)                                 //> res3: weekthree.Rational = -79/42


}
class Rational(x: Int,y: Int){
	def numer = x
	def denom = y

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

		override def toString = numer + "/" + denom

	def neg: Rational = new Rational(-numer,denom)

	def sub(that: Rational) = add(that.neg)

}
###################################### 分数类 ########################################
//////////////////////////////////////////////////////////////////////////////////////