smo*_*ers 5 ruby regex string grammar metaprogramming
我想输入一个字符串并返回一个可用于描述字符串结构的正则表达式.正则表达式将用于查找与第一个相同结构的更多字符串.
这是故意模棱两可的,因为我肯定会错过SO社区中的某个人会抓住的案例.
请发布任何和所有可能的方法来执行此操作.
Con*_*ion 12
琐碎的答案,可能不是你想要的,是:返回输入字符串(带有正则表达式特殊字符转义).这始终是与字符串匹配的正则表达式.
如果您希望识别某些结构,则必须提供有关您希望识别的结构类型的更多信息.没有这些信息,问题就会以模棱两可的方式陈述,并且有许多可能的解决方案.例如,输入字符串'aba'可以描述为
'ABA'
'ABA*'
'ABA？'
'AB\W'
'\瓦特{3}'
'().B\1'
等等
小智 6
对不起这个长度.我把这个作为一个小挑战的前提,并在Ruby中提出了一个概念证明.
我的假设是你可以提供一些与正则表达式(HITS)匹配的字符串和一个不匹配的数字(MISSES).
我将代码基于遗传算法的简单实现.请参阅底部的注释,了解我对此方法成功与否的看法.
LOOP_COUNT = 100
class Attempt
# let's try email
HITS = %w[j@j.com j@j.co.uk gates@microsoft.com sales@microsoft.com sjobs@apple.com sales@apple.com frddy@aol.com thing1@charity.org sales@mybad.org.uk thing.one@drseuss.com]
MISSES = %w[j@j j@j@.com j.com @domain.com nochance eric@google. eric@google.com. username-at-domain-dot-com linux.org eff.org microsoft.com sjobs.apple.com www.apple.com]
# odd mixture of numbers and letters, designed to confuse
# HITS = %w[a123 a999 a600 a545 a100 b001 b847 a928 c203]
# MISSES = %w[abc def ghi jkl mno pqr stu vwx xyz h234 k987]
# consonants versus vowels
# HITS = %w[bcd cdb fgh ghf jkl klj mnp npm qrs srq tvw vwt xzb bzx]
# MISSES = %w[aei oyu oio euu uio ioe aee ooo]
# letters < 11 chars and no numbers
# HITS = %w[aaa aaaa abaa azaz monkey longstring stringlong]
# MISSES = %w[aa aa1 aa0 b9b 6zz longstringz m_m ff5 666 anotherlongstring]
MAX_SUCCESSES = HITS.size + MISSES.size
# Setup the various Regular Expression operators, etc..
RELEMENTS = %w[. ? * + ( ) \[ \] - | ^ $ \\ : @ / { }]
%w[A b B d D S s W w z Z].each do |chr|
RELEMENTS << "\\#{chr}"
end
%w[alnum alpha blank cntrl digit lower print punct space upper xdigit].each do |special|
RELEMENTS << "[:#{special}:]"
end
('a'..'z').each do |chr|
RELEMENTS << chr
end
('A'..'Z').each do |chr|
RELEMENTS << chr
end
(0..9).each do |chr|
RELEMENTS << chr.to_s
end
START_SIZE = 8
attr_accessor :operators, :successes
def initialize(ary = [])
@operators = ary
if ary.length < 1
START_SIZE.times do
@operators << random_op
end
end
@score = 0
@decay = 1
make_regexp
end
def make_regexp
begin
@regexp = Regexp.new( @operators.join("") )
rescue
# "INVALID Regexp"
@regexp = nil
@score = -1000
end
end
def random_op
RELEMENTS[rand(RELEMENTS.size)]
end
def decay
@decay -= 1
end
def test
@successes = 0
if @regexp
HITS.each do |hit|
result = (hit =~ @regexp)
if result != nil
reward
end
end
MISSES.each do |miss|
result = (miss =~ @regexp)
if result == nil
reward
end
end
end
@score = @successes
self
end
def reward
@successes += 1
end
def cross other
len = size
olen = other.size
split = rand(len)
ops = []
@operators.length.times do |num|
if num < split
ops << @operators[num]
else
ops << other.operators[num + (olen - len)]
end
end
Attempt.new ops
end
# apply a random mutation, you don't have to use all of them
def mutate
send [:flip, :add_rand, :add_first, :add_last, :sub_rand, :sub_first, :sub_last, :swap][rand(8)]
make_regexp
self
end
## mutate methods
def flip
@operators[rand(size)] = random_op
end
def add_rand
@operators.insert rand(size), random_op
end
def add_first
@operators.insert 0, random_op
end
def add_last
@operators << random_op
end
def sub_rand
@operators.delete_at rand(size)
end
def sub_first
@operators.delete_at 0
end
def sub_last
@operators.delete_at size
end
def swap
to = rand(size)
begin
from = rand(size)
end while to == from
@operators[to], @operators[from] = @operators[from], @operators[to]
end
def regexp_to_s
@operators.join("")
end
def <=> other
score <=> other.score
end
def size
@operators.length
end
def to_s
"#{regexp_to_s} #{score}"
end
def dup
Attempt.new @operators.dup
end
def score
if @score > 0
ret = case
when (size > START_SIZE * 2)
@score-20
when size > START_SIZE
@score-2
else
@score #+ START_SIZE - size
end
ret + @decay
else
@score + @decay
end
end
def == other
to_s == other.to_s
end
def stats
puts "Regexp #{@regexp.inspect}"
puts "Length #{@operators.length}"
puts "Successes #{@successes}/#{MAX_SUCCESSES}"
puts "HITS"
HITS.each do |hit|
result = (hit =~ @regexp)
if result == nil
puts "\tFAIL #{hit}"
else
puts "\tOK #{hit} #{result}"
end
end
puts "MISSES"
MISSES.each do |miss|
result = (miss =~ @regexp)
if result == nil
puts "\tOK #{miss}"
else
puts "\tFAIL #{miss} #{result}"
end
end
end
end
$stderr.reopen("/dev/null", "w") # turn off stderr to stop streams of bad rexexp messages
# find some seed attempt values
results = []
10000.times do
a = Attempt.new
a.test
if a.score > 0
# puts "#{a.regexp_to_s} #{a.score}"
results << a
end
end
results.sort!.reverse!
puts "SEED ATTEMPTS"
puts results[0..9]
old_result = nil
LOOP_COUNT.times do |i|
results = results[0..9]
results.map {|r| r.decay }
3.times do
new_results = results.map {|r| r.dup.mutate.test}
results.concat new_results
new_results = results.map {|r| r.cross( results[rand(10)] ).test }
results.concat new_results
end
new_results = []
20.times do
new_results << Attempt.new.test
end
results.concat new_results
results.sort!.reverse!
if old_result != results[0].score
old_result = results[0].score
end
puts "#{i} #{results[0]}"
end
puts "\n--------------------------------------------------"
puts "Winner! #{results[0]}"
puts "--------------------------------------------------\n"
results[0].stats
玩这个代码的经验教训.
总的来说,似乎多次运行较短的循环最有可能产生可用的结果.然而,这可能是由于我的实施而不是遗传算法的本质.
您可能会得到有效但仍包含乱码的部分的结果.
您将需要非常牢固地掌握正则表达式,以了解有多少结果实际上实现了它们的功能.
最后,花在学习正则表达式上的时间要好于尝试将此代码用作快捷方式.我意识到提问者可能没有这种动机,我尝试这个的原因是因为这是一个有趣的想法.
结果中存在许多权衡因素.您提供的HITS和MISSES越多样化,产生结果所需的时间越长,您必须运行的循环越多.每个较少的结果可能会产生一个结果,该结果要么大量特定于您提供的字符串,要么非常通用,以至于它在现实世界中不会有用.
我还对一些假设进行了硬编码,例如标记过长的表达式.