Note FOR Ruby 1.9 (2)

10.Ruby之Array,Hash,Set,Matrix/Vector:

• Array:
创建一个Array：
arr = Array.new(3, "baron")
for i in arr
     print " " << i
end

Array比较<=>：
小于返回-1，等于返回0，大于返回1
改写比较方式,可以使用<, ==, >进行比较：
class MyArray < Array
     include Comparable

     def <=>(anotherArray)
         self.length <=> anotherArray.length
     end
end

myarr1 = MyArray.new([0, "ab", "c"])
myarr2 = MyArray.new([1, 2])

p myarr1 <=> myarr2

Array.sort:
arr2 = ["one", "b", "abcde", 1, 3]
sort_arr2 = arr2.sort {
     |a, b|
     a.to_s <=> b.to_s
}
p sort_arr2

Array运算：

1. &: 交
2. +: 并
3. -: 差
4. <<: 添加
Array.flatten:
arr = [1, 2, 3, [4, 5]]
p arr.flatten


• Hash:
创建Hash:
hash = Hash.new("Default")
hash['b'] = "ccc"
p hash
p hash.default

Hash.sort:
用法和Array类似

11.Ruby之循环

• for ... in ... do
  end
  
• ... .each do |...|
  end
  
• while ... do
  end
  
• begin
  end while ...
  
• until ... do
  end
  
• begin
  end until ...
  
• loop {
  }
  

12.Ruby之条件

• 条件运算符，Ruby有两套，而且优先级不同，最好不要混用
1. and, or, not
2. &&, ||, !
3. === 相当于 include?
• if ... then ... elsif ... then ... else ... end
• begin ... end if ...
• begin ... end unless ...
• case ... when ... else ... end
  case返回值为when的最后一条语句
• catch,throw:
  catch (Symbol) {
  ...
  throw Symbol
  ...
  }

13.Ruby之Enumerable：
Ruby中的Array已经包括Enumerable模块,其中包含了include?, collect, min, max方法：
arr = [1, 2, 3, 4, 5]
p arr.include?(3)
p arr.collect{ |i| i * i}
p arr.min
p arr.max

可以自定义min, max的行为：
hash = {"one" => "Monday", "two" => "Tuesday"}
p hash.min{|a, b| a[1].length <=> b[1].length}

each, yield用法
class MyCollection
     include Enumerable

     def initialize(someItems)
         @items = someItems
     end

     def each
         @items.each { |i| yield(i) }
     end
end

things = MyCollection.new(['x', 'yz', 'defgh', 'ij', 'klmno'])
p things.min
p things.max
p things.collect{ |i| i.upcase }
当调用min,max,collect等方法时，其会调用each方法