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=begin
条件判断语句包括if语句，unless语句，case语句，
=end
#if 语句
=begin
if 条件 then
处理1
elsif 条件2 then
处理2
else
处理3
end
=end
a = 10
b = 20
if a > b
puts "a bigger than b"
elsif a < b
puts "a smaller than b"
else
puts "a is equal to b"
end
puts "a bigger than b" if a > b
#unless 语句，与if语句相反，条件判断为假的时执行处理
=begin
unless 条件
处理1
else
处理2
end
=end
a = 10
b = 20
unless a > b
puts "a smaller/same as than b"
end
#case 语句,适用于比较的对象只有一个的时候，根据这个对象的值不同，执行不同的处理;when可以一次指定多个值
=begin
case 比较对象
when 值1 then
处理1
when 值2 then
处理2
when 值3 then
处理3
else
处理4
end
=end
tags = ["A", "IMG", "PRE"]
tags.each do |word|
case word
when "P", "A", "I", "B", "BLOCKQUOTE"
puts "#{word} has child."
when "IMG", "BR"
puts "#{word} has child."
else
puts "#{word} cannoot be used"
end
end
array = ["a", 1, nil]
array.each do |word|
case word
when String
puts "the word is a String"
when Numeric
puts "the word is a Numeric"
else
puts "other words are Something"
end
end
text.each_line do |line|
case line
when /^From:/i
puts "find a sender"
when /^To:/i
puts "find a receiver"
when /^$/
puts "resolution are finnished"
exit
else
break
end
end