Best of Ruby Quiz - MadLib
题目大意明确,主要在于正则表达式运用
1]
首先是自己写的程序
str = %q{Our favorite language is ((gem:a gemstone)). We think ((gem)) is
better than ((a gemstone)). }
hash = {}
def read(prompt)
print "Give Me #{prompt}:"
gets.chomp
end
while str =~ /\(\(.*?\)\)/
pre,suc = $`,$'
$& =~ /\(\((.*?)\:(.*?)\)\)|\(\((.*?)\)\)/
key , prompt = $1 || $3 , $2 || $3
hash[key] ||= read(prompt)
str = pre + hash[key] + suc
end
better than ((a gemstone)). }
hash = {}
def read(prompt)
print "Give Me #{prompt}:"
gets.chomp
end
while str =~ /\(\(.*?\)\)/
pre,suc = $`,$'
$& =~ /\(\((.*?)\:(.*?)\)\)|\(\((.*?)\)\)/
key , prompt = $1 || $3 , $2 || $3
hash[key] ||= read(prompt)
str = pre + hash[key] + suc
end
print str + "\n"
属于比较正常的算法型想法,流式替换过程
2]
然后是书上的程序,最简短的那个
1str = %q{Our favorite language is ((gem:a gemstone)). We think ((gem)) is
2better than ((a gemstone)). }
3hash = Hash.new do |hash,key|
4 print "Give Me #{key.sub /\A([^:]+):/,"" } :"
5 #p $1
6 hash[$1] = gets.chomp
7end
8puts str.gsub(/\(\(([^\)]+)\)\)/){hash[$1]}
9#puts str.gsub(/\(\(([^\)]+)\)\)/ , hash[$1])
2better than ((a gemstone)). }
3hash = Hash.new do |hash,key|
4 print "Give Me #{key.sub /\A([^:]+):/,"" } :"
5 #p $1
6 hash[$1] = gets.chomp
7end
8puts str.gsub(/\(\(([^\)]+)\)\)/){hash[$1]}
9#puts str.gsub(/\(\(([^\)]+)\)\)/ , hash[$1])
稍微有些出入,大体一样
做一些分析:
[0]这个程序存在BUG,如果把第五行注释解开,可以看到输出的第一个$1 = "gem" ,第二个$2 = "nil",BUG在后面我的改进里有修正
[1]第八行用gsub的Block形式十分重要,以下是Programming Ruby的节选
gsub
带有block的形式,当前的匹配会作为参数传入block,并且会适当设置$1,$2,$`,$&,$'等变量
带有block的形式,当前的匹配会作为参数传入block,并且会适当设置$1,$2,$`,$&,$'等变量
如果用第9行的形式,会出现$1 = nil 的错误,因为用参数形式$1不能正确配置
修正后的程序
1str = %q{Our favorite language is ((gem:a gemstone)). We think ((gem)) is
2better than ((a gemstone)). }
3hash = Hash.new do |hash,key|
4 print "Give Me #{key.sub /^([^:]+):/,"" } :"
5 #p $1 || key
6 hash[$1 || key] = gets.chomp
7end
8puts str.gsub(/\(\(([^\)]+)\)\)/){hash[$1]}
2better than ((a gemstone)). }
3hash = Hash.new do |hash,key|
4 print "Give Me #{key.sub /^([^:]+):/,"" } :"
5 #p $1 || key
6 hash[$1 || key] = gets.chomp
7end
8puts str.gsub(/\(\(([^\)]+)\)\)/){hash[$1]}
修正的结果可以将注释行解开验证