Ruby编程语言学习笔记1

对应Ruby编程语言第一章  

#coding:utf-8
#Blocks and Iterators(代码块和迭代器)
#times and upto downto是由Integer实现的迭代器
#times {|i| block }:Iterates block int times, passing in values from zero to int - 1.
puts "#times {|i| block }:"   
5.times do |i|
    print i, " "
    print "\n"
  end
3.times{print "Welcome to Ruby ,Jeriffe\n"}
#upto(limit) {|i| block }:Iterates block, passing in integer values from int up to and including limit.
print"\n"
puts "#upto(limit) {|i| block }:"  
1.upto(9){|x| print x," "}
print"\n"
#downto(limit) {|i| block }:Iterates block, passing in integer values from int down to and including limit.
print"\n"
puts "#downto(limit) {|i| block }:" 
9.downto(1){|x| print x," "}
print"\n"
#数组（及类似的”可枚举的“对象）定义了一个each迭代器
#each {|item| block }:Calls block once for each element in self, passing that element as a parameter.
print"\n"
puts "#each {|item| block }:"   
a=[3,2,1]
a.each{|item| print item,' '}
print"\n"
#在each迭代器基础上定义的其他迭代器
print"\n"
puts "#在each迭代器基础上定义的其他迭代器:"   
a=[1,2,3,4]
b=a.map{|item| item*item}
print b,"\n"
c=a.select{|item| item%2==0}
print c,"\n"
d=a.inject do|sum,item|
  sum+item
end
print d,"\n"
#Methods(方法)
#方法用def关键字来定义，方法的返回值是方法最后一个被执行的表达式
def square(x)
  x*x
end
print square(5),"\n"
#Assignment(赋值)
#除传统的=操作符赋值外，Ruby还支持并行赋值：一个表达式中出现多余一个的值和变量
puts" 并行赋值："
x,y=1,2
print "x=",x,',y=',y,"\n"
x,y=y,x
print "x=",x,',y=',y,"\n"
#方法返回多个值
puts"#方法返回多个值:"
def polar(x,y)
  theta=Math.atan2(y,x)
  r=Math.hypot(x,y)
  [r,theta]
end
distance,angle=polar(2,3)
print "distance=",distance,',angle=',angle,"\n"