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• Best way to parse command line arguments in C#

  - by Paul Stovell

  When building console applications that take parameters, you can use the arguments passed to Main(string[] args). In the past I've simply indexed/looped that array and done a few regular expressions to extract the values. However, when the commands get more complicated, the parsing can get pretty ugly. More recently, I built the world's simplest Backus-Naur Form parser in C# to parse the arguments. It does the job, but it also feels like overkill. So I'm interested in: Libraries that you use Patterns that you use Assume the commands always adhere to common standards such as answered here.

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• How to regex match a string of alnums and hyphens, but which doesn't begin or end with a hyphen?

  - by Shahar Evron

  I have some code validating a string of 1 to 32 characters, which may contain only alpha-numerics and hyphens ('-') but may not begin or end with a hyphen. I'm using PCRE regular expressions & PHP (albeit the PHP part is not really important in this case). Right now the pseudo-code looks like this: if (match("/^[\p{L}0-9][\p{L}0-9-]{0,31}$/u", string) and not match("/-$/", string)) print "success!" That is, I'm checking first that the string is of right contents, doesn't being with a '-' and is of the right length, and then I'm running another test to see that it doesn't end with a '-'. Any suggestions on merging this into a single PCRE regular expression? I've tried using look-ahead / look-behind assertions but couldn't get it to work.

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• How to sift idioms and set phrases apart from other common phrases using NLP techniques?

  - by hippietrail

  What techniques exist that can tell the difference betwen plain common phrases such as "to the", "and the" and set phrases and idioms which have their own lexical meanings such as "pick up", "fall in love", "red herring", "dead end"? Are there techniques which are successful even without a dictionary, statistical methods HMMs train on large corpora for instance? Or are there heuristics such as ignoring or weighting down "promiscuous" words which can co-occur with just about any word versus words which occur either alone or in a specific limited set of idiomatic phrases? If there are such heuristics, how do we take into account set phrases and verbal phrases which do incorporate promiscuous words such as "up" in "beat up", "eat up", "sit up", "think up"? UPDATE I've found an interesting paper online: Unsupervised Type and Token Identi?cation of Idiomatic Expressions

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• Expression Tree : C#

  - by nettguy

  My understanding of expression tree is : Expression trees are in-memory representation of expression like arithmetic or boolean expression.The expressions are stored into the parsed tree.so we can easily transalate into any other language. Linq to SQL uses expression tree.Normally when our LINQ to SQL query compiler translates it to parsed expression trees.These are passed to Sql Server as T-SQL Statements.The Sql server executes the T-SQL query and sends down the result back.That is why when you execute LINQ to SQL you gets IQueryable<T> not IEnumetrable<T>.Because IQuerybale contains public IQueryable:IEnumerable { Type Element {get;} Expression Expression {get;} IQueryaleProvider Provider {get;} } Questions : Microsoft uses Expression trees to play with LINQ-to-Sql.What are the different ways can i use expression trees to boost my code. Apart from LINQ to SQL,Linq to amazon ,who used expression trees in their applications? Linq to Object return IEnumerable,Linq to SQL return IQueryable ,What does LINQ to XML return?

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• How to handle an "infinite" IEnumerable?

  - by Danvil

  A trivial example of an "infinite" IEnumerable would be IEnumerable<int> Numbers() { int i=0; while(true) { yield return i++; } } I know, that foreach(int i in Numbers().Take(10)) { Console.WriteLine(i); } and var q = Numbers(); foreach(int i in q.Take(10)) { Console.WriteLine(i); } both work fine (and print out the number 0-9). But are there any pitfalls when copying or handling expressions like q? Can I rely on the fact, that they are always evaluated "lazy"? Is there any danger to produce an infinite loop?

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• Listing mysql row entries from tags into one single row

  - by Derrick

  Hi guys, Ive got two tables, one a listings and another representing a list of tags for the listing table. In the listings table the tag ids are stored in a field called tags as 1-2-3- this has worked out very well for me regular expressions and joins to seperate and display the data, BUT... I now need to pull the titles of those tags into a single row. See below. listings table id tags 1 1-2-3- 2 4-5-6- tags table id title 1 pig 2 dog 3 cat 4 mouse 5 elephant 6 duck And what I need to produce out of the listings table is: id tags 2 mouse, elephant, duck any suggestions?

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• How to handle subclasses in JasperReports?

  - by gotch4

  I've two classes (A and B) that extend a base class BASE. I need to make a report that takes an array of such classes and the prints the fields of A or B. I tought of using conditional expressions, then casting to one or another (depending on a field value). But I can't cast, because I don't know how to refere to the current bean. To do this I am using a JRBeanCollectionDataSource filled with a List<BASE>. How do I cast every bean to A or B in a report (or subreport)? I tried: ((A)this) but it says basically that this contains the report instance, not the current bean and gives error.

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• Regex pattern for searches with include and exclude

  - by alex-kravchenko-zmeyp

  I am working on a Regex pattern for searches that should allow optional '+' sign to include in the search and '-' sign to exclude from the search. For example: +apple orange -peach should search for apples and oranges and not for peaches. Also the pattern should allow for phrases in double quotes mixed with single words, for example: "red apple" -"black grape" +orange - you get the idea, same as most of the internet searches. So I am running 2 regular expressions, first to pick all the negatives, which is simple because '-' is required: (?<=[\-]"?)((?<=")(?<exclude>[^"]+)|(?<exclude>[^\s,\+\-"]+)) And second to pick positives, and it is a little more complex because '+' is optional: ((?<=[\+\s]")(?<include>[^\s"\+\-][^"]+))|(?<include>(?<![\-\w]"?)([\w][^,\s\-\+]+))(?<!") Positive search is where I am having a problem, it works fine when I run it in RegexBuddy but when I try in .Net the pattern picks up second word from negative criteria, for example in -"black grape" it picks up word 'grape' even though it ends with double quote. Any suggestions?

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• How to extract URL parameters from a URL with Ruby or Rails?

  - by Flackou

  Hi, I have some URLs, like http://www.example.com/something?param1=value1&param2=value2&param3=value3, and I would like to extract the parameters from these URLs and get them in a Hash. Obviously, I could use regular expressions, but I was just wondering if there was easier ways to do that with Ruby or Rails. I haven't found anything in the Ruby Module 'URI' but perhaps I missed something. In fact, I need a method that would do that : extract_parameters_from_url("http://www.example.com/something?param1=value1&param2=value2&param3=value3") => {:param1 => 'value1', :param2 => 'value2', :param3 => 'value3'} Would you have some advices? Thanks in advance. Julien

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• Why does Excel expose an 'Evaluate' method at all?

  - by jtolle

  A few questions have come up recently involving the Application.Evaluate method callable from Excel VBA. The old XLM macro language also exposes an EVALUATE() function. Both can be quite useful. Does anyone know why the general expression evaluator is exposed, though? My own hunch is that Excel needed to give people a way to get ranges from string addresses, and to get the value of named formulas, and just opening a portal to the expression evaluator was the easiest way. But of course you don't need the ability to evaluate arbitrary expressions just to do that. Application.Evaluate seems kind of...unfinished. It isn't very well documented, and there are quite a few quirks and limitations (as described by Charles Williams here: http://www.decisionmodels.com/calcsecretsh.htm) with what is exposed. I suppose the answer could be simply "why not expose it?", but I'd be interested to know what design decisions led to this feature. Failing that, I'd be interested to hear other hunches.

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• Numbering Regex Submatches

  - by gentlylisped

  Is there a canonical ordering of submatch expressions in a regular expression? For example: What is the order of the submatches in "(([0-9]{3}).([0-9]{3}).([0-9]{3}).([0-9]{3}))\s+([A-Z]+)" ? a. (([0-9]{3})\.([0-9]{3})\.([0-9]{3})\.([0-9]{3}))\s+([A-Z]+) (([0-9]{3})\.([0-9]{3})\.([0-9]{3})\.([0-9]{3})) ([A-Z]+) ([0-9]{3}) ([0-9]{3}) ([0-9]{3}) ([0-9]{3}) b. (([0-9]{3})\.([0-9]{3})\.([0-9]{3})\.([0-9]{3}))\s+([A-Z]+) (([0-9]{3})\.([0-9]{3})\.([0-9]{3})\.([0-9]{3})) ([0-9]{3}) ([0-9]{3}) ([0-9]{3}) ([0-9]{3}) ([A-Z]+) or c. somthin' else.

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• Regular expression to match one of two video ID's in a Google Video URL

  - by Baldur

  I need to grab the video ID from a Google Video URL. There are two different types of URLs that I need to be able to match: http://video.google.com/videoplay?docid=-3498228245415745977# where I need to be able to match -3498228245415745977 (note the dash; -), and video.google.com/videoplay?docid=-3498228245415745977#docid=2728972720932273543 where I need to match 2728972720932273543. Is there any good regular expression that can match this? This is what I've got so far: @"docid=(-?\d{19}+)" since the video ID seems to be 19 characters except when it's prefixed with the dash. I'm using C# (of which I have very little experience) if that changes anything. P.s. I would also appreciate you review my regular expressions for YouTube (@"[\?&]v=([^&#])";), RedTube (@"/(\d{1,6})") and Vimeo (@"/(\d*)"). I do not expect users to enter the full URL and thus do not match the ^http://\\.?sitename+\\.\\w{2,3}.

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• Python regular expression help

  - by dlw

  Hi SO, I can't seem to create the correct regular expression to extract the correct tokens from my string. Padding the beginning of the string with a space generates the correct output, but seems less than optimal: >>> import re >>> s = '-edge_0triggered a-b | -level_Sensitive c-d | a-b-c' >>> re.findall(r'\W(-[\w_]+)',' '+s) ['-edge_0triggered', '-level_Sensitive'] # correct output Here are some of the regular expressions I've tried, does anyone have a regex suggestion that doesn't involve changing the original string and generates the correct output >>> re.findall(r'(-[\w_]+)',s) ['-edge_0triggered', '-b', '-level_Sensitive', '-d', '-b', '-c'] >>> re.findall(r'\W(-[\w_]+)',s) ['-level_Sensitive'] Thanks -- DW

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• Math with interpolated variables?

  - by Idan Gazit

  Consider the following sass: $font-size: 18; $em: $font-size; $column: $font-size * 3; // The column-width of my grid in pixels $gutter: $font-size * 1; // The gutter-width of my grid in pixels $gutter-em: #{$gutter / $em}em; // The gutter-width in ems. $column-em: #{$column / $em}em; // The column-width in ems; $foo = $gutter-em / 2; // This results in a value like "1em/2". :( $bar = ($gutter-em / 2); // this doesn't work either, same as above. How can I generate a $foo that works, and that I can reuse further in other expressions?

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• How can I replace only the last occurence of an number in a string with php?

  - by Shawn

  How would you change this: a-10-b-19-c into something like this: a-10-b-20-c using regular expressions in PHP? The only solution I've found so far is: reverse the original string - "c-91-b-01-a" find the first number - "91" reverse it - "19" turn in into a number (parseInt) - 19 add 1 to it (+1) - 20 turn it into a string again (toString) - "20" reverse it again - "02" replace the original match with this new number - "c-02-b-01-a" reverse the string - "a-10-b-20-c" I was hoping someone on SO would have a simpler way to do this... Anyone?

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• Efficient data structure design

  - by Sway

  Hi there, I need to match a series of user inputed words against a large dictionary of words (to ensure the entered value exists). So if the user entered: "orange" it should match an entry "orange' in the dictionary. Now the catch is that the user can also enter a wildcard or series of wildcard characters like say "or__ge" which would also match "orange" The key requirements are: * this should be as fast as possible. * use the smallest amount of memory to achieve it. If the size of the word list was small I could use a string containing all the words and use regular expressions. however given that the word list could contain potentially hundreds of thousands of enteries I'm assuming this wouldn't work. So is some sort of 'tree' be the way to go for this...? Any thoughts or suggestions on this would be totally appreciated! Thanks in advance, Matt

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• Merging MySQL row entries into a single row

  - by Derrick

  I've got two tables, one for listings and another representing a list of tags for the listings table. In the listings table the tag ids are stored in a field called tags as 1-2-3-. This has worked out very well for me (regular expressions and joins to separate and display the data), but I now need to pull the titles of those tags into a single row. See below. listings table id tags 1 1-2-3- 2 4-5-6- tags table id title 1 pig 2 dog 3 cat 4 mouse 5 elephant 6 duck And what I need to produce out of the listings table is: id tags 2 mouse, elephant, duck

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• C# Lambda Problem

  - by Chris Klepeis

  Probably something simple, but as I'm new to lambda expressions, the problem evades me: m => m.contactID == contactID && m.primaryAddress == true && (m.addressTypeID == 2 || m.addressTypeID == 3) I tried to use that lambda expression but I receive an invalid operator. Is there a way to simplify this so that it would work? Edit: The equivolent sql query would be: SELECT * FROM Contact WHERE contactID = 3 AND primaryAddress = 1 AND (addressTypeID = 2 OR addressTypeID = 3) I have a repository function defined like so: public E Single(Expression<Func<E, bool>> where) { return objectSet.Single<E>(where); } I'm passing the lambda expression above into this function. Invalid operator error.

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• Using C# and gppg, how would I construct an abstract syntax tree?

  - by Rupert

  Is there a way to do this almost out-of-the-box? I could go and write a big method that would use the collected tokens to figure out which leaves should be put in which branches and in the end populate a TreeNode object, but since gppg already handled everything by using supplied regular expressions, I was wondering if there's an easier way? Even if not, any pointers as to how best to approach the problem of creating an AST would be appreciated. Apologies if I said anything silly, I'm only just beginning to play the compiler game. :)

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• Regular Expression for finding phone numbers

  - by Rocky

  Hello Everyone, I am new to Stackoverflow and I have a quick question. Let's assume we are given a large number of HTML files (large as in theoretically infinite). How can I use Regular Expressions to extract the list of Phone Numbers from all those files? Explanation/expression will be really appreciated. The Phone numbers can be any of the following formats: (123) 456 7899 (123).456.7899 (123)-456-7899 123-456-7899 123 456 7899 1234567899 Thanks a lot for all your help and have a good one!

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• Do comments slow down an interpreted language?

  - by mvid

  I am asking this because I use Python, but it could apply to other interpreted languages as well (ruby, php). Whenever I leave a comment in my code, is it slowing down the interpreter? My limited understanding of an interpreter is that it reads program expressions in as strings and converts those strings into code. It seems that every time it parses a comment, that is wasted time. Is this the case? Is there some convention for comments in interpreted languages, or is the effect negligible?

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• Can a Domain Specific Language (DSL) be localized?

  - by michielvoo

  I have never written a DSL, but I am considering it as a feature for a new project (hypothetical). It would be for end users to be able to express in natural language concepts such as weekdays between 10 and 11 except on the first monday of the month. Dutch users might write weekdagen tussen 10 en 11 behalve op de eerste maandag van de maand. In this case the position of the words seems to match, but there may be expressions where the position of verbs/nouns etc. could be different between languages. I realise the obvious answer (it depends). I am a .NET developer and I consider using Boo but I'm open to suggestions. I need to understand wether each translation requires rewriting a part of the implementation (which part) or if there is a way to do actual translations, maybe in some sort of preprocessor. Thanks!

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• How can I remove sensitive data from the debug_backtrace function?

  - by RenderIn

  I am using print_r(debug_backtrace(), true) to retrieve a string representation of the debug backtrace. This works fine, as print_r handles recursion. When I tried to recursively iterate through the debug_backtrace() return array before turning it into a string it ran into recursion and never ended. Is there some simple way I can remove certain sensitive key/value pairs from the backtrace array? Perhaps some way to turn the array to a string using print_r, then back to an array with the recursive locations changed to the string RECURSION, which I could the iterate through. I don't want to execute regular expressions on the string representation if possible.

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• A compiler for automata theory

  - by saadtaame

  I'm designing a programming language for automata theory. My goal is to allow programmers to use machines (DFA, NFA, etc...) as units in expressions. I'm confused whether the language should be compiled, interpreted, or jit-compiled! My intuition is that compilation is a good choice, for some operations might take too much time (converting NFA's to equivalent DFA's can be expensive). Translating to x86 seems good. There is one issue however: I want the user to be able to plot machines. Any ideas?

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• Are Scala "continuations" just a funky syntax for defining and using Callback Functions?

  - by Alex R

  And I mean that in the same sense that a C/Java for is just a funky syntax for a while loop. I still remember when first learning about the for loop in C, the mental effort that had to go into understanding the execution sequence of the three control expressions relative to the loop statement. Seems to me the same sort of effort has to be applied to understand Continuations (in Scala and I guess probably other languages). And then there's the obvious follow-up question... if so, then what's the point? It seems like a lot of pain (language complexity, programmer errors, unreadable programs, etc) for no gain.

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