七周七语言：Io Day 2

第二天

今天做这些花了几乎一个下午……主要原因是要查iolanguage.org上的文档，而且那个文档不知道为什么不能搜索 :(
这“一天”的内容，关于Io的控制语句、文件IO、错误处理、列表都有涉及。

个人比较喜欢的是Io的控制语句，写在一个()里，没有else，条件、语句都用一个comma隔开的感觉很不错；
有点不理解的是关于Io的消息机制和反射，虽然书上的例子举的比较清楚，可是还是觉得将其称之为“反射”比较不习惯；再者，关于原型和对象的关系，感觉就是类的继承（？！）……好吧，学习一门语言的过程还是挺欢乐的～

• 计算fibonacci数列

  #循环的方法
  array := List clone
  array := list(1, 1)
  #change the value of a to cal fib(a)
  a ::= 10
  for(i, 2, a, 1, array append(array at(i-1) + array at(i-2)) println)
  #Output
  list(1, 1, 2)
  list(1, 1, 2, 3)
  list(1, 1, 2, 3, 5)
  list(1, 1, 2, 3, 5, 8)
  list(1, 1, 2, 3, 5, 8, 13)
  list(1, 1, 2, 3, 5, 8, 13, 21)
  list(1, 1, 2, 3, 5, 8, 13, 21, 34)
  list(1, 1, 2, 3, 5, 8, 13, 21, 34, 55)
  list(1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89)
  ==> list(1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89)
  #递归的方法
  fib := method( n,
          if(((n == 1) or (n == 2)),return(1))
          #loop until n == i
          reFib := method( n, i, n1, n2,
              if((n == i),return(n1 + n2))
                  return(reFib(n,(i+1),n2,(n2 + n1)))
          )
          #The first condition of reFib
          return(reFib( n, 3, 1, 1))
  )
  fib(1) println
  fib(2) println
  fib(10) println
  #Output
  1
  1
  55
          

• 在分母为0的情况下，如何让运算符返回0？

    Number setSlot("division", Number getSlot("/"))
    
    Number setSlot("/",
       method( denominator,
             if((denominator == 0),return (0))
             return(self division( denominator))
          )
    )
    
    (1 / 0) println
    (2 / 1) println
    #Output
    0
    2
          

• 对二维数组进行求和

  #Define a 2D array
  2d_array := list(
  		 list(1, 2, 3),
  		 list(4, 5, 6),
  		 list(7, 8, 9)
  )
  sum := 0
  #Nested foreach statement
  2d_array foreach(r, r foreach(v, (sum = sum + v)))
  "The sum of this 2D array is: " print
  sum println
  #Output
  The sum of this 2D array is: 45
          

• 对列表增加一个名为myAverage的槽，以计算列表中所有数字的平均值。如果列表没有数字会发生什么？

  List myAverage := method(
  	 sum := 0 
  	 self foreach(k, 
  	 	  if((k type != "Number"),
  		  		Exception raise("There is a NaN-value in the list, please check your list." ),
  		  sum =( sum + k))
  	)
  	return (sum/(self size))
  )
  
  list(1, 2, 3) myAverage println
  list(1, "a", 3) myAverage println
  #Output
  2
    Exception: There is a NaN-value in the list, please check your list.
    ---------
    Exception raise                      myAverage.io 5
    List myAverage                       myAverage.io 13
    CLI doFile                           Z_CLI.io 140
    CLI run                              IoState_runCLI() 1
          

• 对二维列表写一个原型。该原型的dim(x, y)方法可为一个包含y个列表的列表分配内存，其中每个列表都有x个元素，set(x, y)方法可以设置列表中的值，get(x, y)方法可返回列表中的值。

  2DList := List clone
  #This method should be considered later
  2DList dim := method(x, y,
  	   if( (self proto type == "List"),
  	   	   return 2DList clone dim(x, y)
  	   )
  	   self setSize(x)
  	   for(i, 0, (x-1), 1,
  	   		  self atPut(i, (list() setSize(y)))
  	   )
  	   return self
  )
  #set the value at(x) at(y)
  2DList set := method(x, y, value,
  	   self at(x) atPut(y, value)
  	   return self
  )
  #get the value 
  2DList get := method(x, y,
  	   return (self at(x) at(y))
  )
  
  matrix := 2DList clone dim(3, 3)
  for(i, 0, 2, 1, for(n, 0, 2, 1, matrix set(i, n, i+n))) println
  matrix get(1, 1) println
  #Output
  list(list(0, 1, 2), list(1, 2, 3), list(2, 3, 4))
  2 
          

• 把矩阵写入文件，并从文件中读取矩阵。

  #Define a matrix
  matrix := list(
  	   list(1, 2, 3),
  	   list(4, 5, 6),
  	   list(7, 8, 9)
  )
  #Create a new file named test.txt
  data := File open("test.txt")
  #Transform the matrix into a sequence and write it into the file
  data File write(matrix serialized)
  data close
  #Read solution 1: use File open(still a serialized file)
  readData := File open("test.txt")
  readData readLine println
  readData close
  #Read solution 2: use doFile
  readData2 := doFile("test.txt")
  readData2 println
  readData2 close
  #Output
  list(list(1, 2, 3);, list(4, 5, 6);, list(7, 8, 9););
  list(list(1, 2, 3), list(4, 5, 6), list(7, 8, 9))
          

• 写一个猜数字程序。

  #Guess number
  standardIO := File standardInput
  guess := nil
  counter := 0
  #Get a random number between 1~100
  answer := (Random value(99)+1) floor
  
  while( counter < 10,
  	   "Guess a number(1..100):" println
  	   guess := standardIO readLine() asNumber()
  	   if((guess == answer), 
  	   			 "You are right!" println;break,
  				 if((guess > answer), 
  				 		   "Too big" println, 
  				 		   "Too small" println)
  	   )
         counter = counter + 1
  )
  #Output
  Guess a number(1..100):
  50 
  Too small
  Guess a number(1..100):
  75
  Too small
  Guess a number(1..100):
  90
  Too small
  Guess a number(1..100):
  95
  Too big
  Guess a number(1..100):
  93
  Too big
  Guess a number(1..100):
  92
  You are right!