ruby note——Loops and Iterators

1、For Loops

　　ruby中for循环与c++等语言不太一样，c++中通常是条件表达式，确定start，达到end条件后结束for循环。而Ruby中for循环需要列举所有的items，然后一个一个去进行迭代.

eg: 

for i in [1,2,3]

    puts i 

end

 

　 另外each可以做同样的工作，称作“syntax sugar”。Arrays、Sets、Hashes、Strings集合都实现了each method.

eg:

[1,2,3].each do |x|

    puts x

end

 

　　both for and each can be used to iterate over the values in a range

eg:

for i in 1..3

    puts i

end

(1..3).each do |s|

    puts s

end

 

2、Mutiple Iterator Arguments

eg:

mutiarr = [["one","two","three","four"],[1,2,3,4]]
 
for (a,b,c,d) in mutiaar
    print "a=#{a},b=#{b},c=#{c},d=#{d}"
end

 

 3、While Loops

　　

//when condition is true executes sleep
while tired
    sleep
end

//ececuted sleep precedes the test condition 
begin
    sleep
end while tired

4、Until Loops //it can be thought of as a "while not" loop

i = 10

puts(i) until i ==10 //never ececutes

//once executes
bebin
    puts(i)
end until i == 10

5、Loops

puts( "\nloop" )
 i=0 
loop do 
   puts(arr[i])
    i+=1 
    if (i == arr.length) then 
      break 
    end 
end