Ruby_特殊语法糖_Range和if

题目：

def sysout
  while line = gets
    break if line.strip == "OK"
    puts "----"
    puts line if (( a = (line =~ /start/) ) .. (b = (line =~ /end/) ) )
    puts "==== a=#{a}, b=#{b} \n\n"
  end
end

sysout

输入和输出：

 

xx

----

==== a=, b= 

 

yy

----

==== a=, b= 

 

xxxstart

----

xxxstart

==== a=3, b= 

 

zzz

----

zzz

==== a=3, b= 

 

yyyendmm

----

yyyendmm

==== a=3, b=3 

 

mm

----

==== a=, b=3 

 

问题：

#1 为什么会有上面的现象？（什么现象，请仔细看看）

#2 为什么上面的输入zzz处，a的值仍然是3

#3 接着问：3..nil是报错的为什么被当做True，而且没有抛出错误？（难道if会捕获这个异常么）

irb(main):025:0> if( 3 .. nil)
irb(main):026:1>   puts 100
irb(main):027:1> end
100
=> nil
irb(main):028:0> 3 .. nil
ArgumentError: bad value for range
	from (irb):28
	from :0
irb(main):029:0>

 

关闭：

 

If range expression appears in any other place than conditional expression, it returns range object from left hand side to right hand side.

 

If range expression appears in conditional expression, it gives false until left hand side returns true, it stays true until right hand side is true. .. acts like awk, ... acts like sed.

 

参考：ruby的语法：

http://web.njit.edu/all_topics/Prog_Lang_Docs/html/ruby/syntax.html

 

 

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