Comments on: (How|Where) does one find Google's (guide|help) on (searching|querying) using regular expressions?
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions/
Comments on Ask MetaFilter post (How|Where) does one find Google's (guide|help) on (searching|querying) using regular expressions?Thu, 28 Jul 2005 07:28:35 -0800Thu, 28 Jul 2005 07:28:35 -0800en-ushttp://blogs.law.harvard.edu/tech/rss60Question: (How|Where) does one find Google's (guide|help) on (searching|querying) using regular expressions?
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions
Well, what do you know, err.. what do I know, Google does <a href="http://www.google.com/search?hl=en&lr=&safe=off&q=%22%28I%7CHe%7CShe%29+%28can%7Cmay%7Cwill%29+%28search%7Cfind%7Clocate%29%22&btnG=Search">support</a> some sort of regular expressions. However, I can't find the usage guide. Anyone?post:ask.metafilter.com,2005:site.21820Thu, 28 Jul 2005 04:34:41 -0800GyangooglesearchregularexpressionsregexpregexusesyntaxtoolsBy: jessamyn
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions#351521
Here's a <a href="http://ask.metafilter.com/mefi/20374">previous thread</a> on a similar but not identical topic.comment:ask.metafilter.com,2005:site.21820-351521Thu, 28 Jul 2005 07:28:35 -0800jessamynBy: Gyan
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions#351535
I know, I was going to post a comment there, but it's locked.comment:ask.metafilter.com,2005:site.21820-351535Thu, 28 Jul 2005 07:48:35 -0800GyanBy: mendel
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions#351541
It's a big jump from "supports permutations" to "supports regular expressions" -- just like it supporting "*" doesn't mean it supports shell globbing. The "(a|b|c)" notation seems to be identical to the documented "(a OR b OR c)" notation.comment:ask.metafilter.com,2005:site.21820-351541Thu, 28 Jul 2005 07:59:04 -0800mendelBy: majick
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions#351545
I've played quite a bit with search syntax but, no, Google does not support some sort of regular expressions. Perhaps you've been misled as to what a regular expression is?comment:ask.metafilter.com,2005:site.21820-351545Thu, 28 Jul 2005 08:04:51 -0800majickBy: Netzapper
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions#351547
Check out <a href="http://www.googletutor.com/">GoogleTutor</a>.comment:ask.metafilter.com,2005:site.21820-351547Thu, 28 Jul 2005 08:09:45 -0800NetzapperBy: Gyan
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions#351551
mendel <a href='http://ask.metafilter.com/mefi/21820#351541'>:</a> <em>"It's a big jump from 'supports permutations' to 'supports regular expressions'"</em><br>
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I know, that's why I said 'some sort'. Clearly, escape sequences don't work. I know Google can support regex, because my friend who's starting work there in August, has seen it on-campus.comment:ask.metafilter.com,2005:site.21820-351551Thu, 28 Jul 2005 08:24:13 -0800GyanBy: robhuddles
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions#351552
Also see <a href="http://www.googleguide.com">GoogleGuide</a>comment:ask.metafilter.com,2005:site.21820-351552Thu, 28 Jul 2005 08:24:48 -0800robhuddlesBy: Rhomboid
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions#351587
Just because it's something their internal interface supports doesn't mean you'll ever see it available on the external interface. The fact is that plain "keyword" searching is computationally about a million times easier to implement on the google scale than a regular expression DFA / NFA engine. The only possible way to make keyword searching efficient over hundreds of terabytes (or whatever their index is up to these days) is to precompute an index of words.<br>
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In fact a full regex engine is turing-complete, and you can write arbitrary regexps that will gobble up near infinite amounts of CPU time and memory. For all these reasons it would be technical insanity for them to offer regex searching to the general public.comment:ask.metafilter.com,2005:site.21820-351587Thu, 28 Jul 2005 09:36:07 -0800RhomboidBy: grouse
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions#351647
Since you guys want to be so nitpicky about what a regular expression is, it's an expression that defines a regular language. Even a single character is a regular expression. You don't have to have wildcards to have a regular expression. So in some sense, Google has always supported "some sort of" regular expressions. In another, they do not support the full expressiveness of regular expressions.<br>
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<em>In fact a full regex engine is turing-complete</em><br>
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Perl-compatible "regexes" have features that mean a Turing machine is necessary to accept them, but properly speaking the "regular" in regular expressions means that you can accept them with only a finite state automaton.comment:ask.metafilter.com,2005:site.21820-351647Thu, 28 Jul 2005 12:15:58 -0800grouseBy: andrew cooke
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions#351715
ok, it's late, but it seems to me that the best description of google is that it "supports regular expressions over the alphabet consisting of words in web pages except for the implementation of a kleene star".<br>
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gyan's example shows both concatenation and alternation, as long as you remember that the alphabet is words, not letters.<br>
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<a href="http://en.wikipedia.org/wiki/Regular_expression#In_formal_language_theory">wikipedia</a>comment:ask.metafilter.com,2005:site.21820-351715Thu, 28 Jul 2005 14:00:30 -0800andrew cookeBy: andrew cooke
http://ask.metafilter.com/21820/HowWhere-does-one-find-Googles-guidehelp-on-searchingquerying-using-regular-expressions#351717
(although the lack of ordering in most queries - which don't use quotes or plus - can't be described in regular expressions without a kleene star!)comment:ask.metafilter.com,2005:site.21820-351717Thu, 28 Jul 2005 14:02:37 -0800andrew cooke