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Search found 2455 results on 99 pages for 'lambda expressions'.

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• algorithmes with no executable example code

  - by gcc

  [link] http://stackoverflow.com/questions/2932016/parsing-of-mathematical-expressions (problem has been told before) ** program is to create the infix tree for the given math expression.** if the expression is given completely paranthesized then the out put is fine but when there are no paranthesis or some part paranthesized then the out put is wrong. cant get the idea how to solve. my problem is told above. I have some algorithm to solve my problem, but I have no simple code which will be guide for me. Can anyone give me simple code (not working code) so that I will try working to understand.(for a 3 hours ,I have been searching and reading some text to understand algorithm which is told above.Actually,there is no example code investigating how it is working. Can anyone send me example which is written in c not other language.

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• Doxygen C++ comment string parser in python?

  - by Sebastian

  Does anybody know of a python module to parse a doxygen style C++ comment string? I mean a string like this (simple example): /** * A constructor. * A more elaborate description of the constructor. * @param param1 test1 * @param param2 test2 */ and I would like to extract the brief, the long description, the parameters, the return value etc. I'm currently doing this using string methods and regular expressions but my solution is not very robust. Alternatively can anybody recommend an easy to use python parser lib that I can set up quickly? Thanks in advance

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• Would it be simply better to use the system's functions rather than use the language?

  - by Nullw0rm

  There are many scenarios where I've questioned PHP's performance with some of its functions, and whether I should build a complex class to handle specific things using its seemingly slow tools. For example, Complex regular expressions with sed and processing with awk would seemingly be exponential in performance rather than making PHP's regular expression and seemingly excessive functions parse and in time manage to finish it. If I were to do a lot of network tasks such as MX lookups/DIGging/retrieving simultaneously I would rather pass it via system() and let the OS handle it itself. There are simply too many functions in PHP, that are inefficient and result in slow pages or can be handled easier by the OS. What are your opinions? Do you think I should do the hard work with the OS in its own/custom functions?

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• Is there an easy way in Python to wait until certain condition is true?

  - by Checkers

  I need to wait in a script until a certain number of conditions become true? I know I can roll my own eventing using condition variables and friends, but I don't want to go through all the trouble of implementing it, since some object property changes come from external thread in a wrapped C++ library (Boost.Python), so I can't just hijack __setattr__ in a class and put a condition variable there, which leaves me with either trying to create and signal a Python condition variable from C++, or wrap a native one and wait on it in Python, both of which sound fiddly, needlessly complicated and boring. Is there an easier way to do it, barring continuous polling of the condition? Ideally it would be along the lines of res = wait_until(lambda: some_predicate, timeout) if (not res): print 'timed out'

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• C# ToDictionary can valueSelector give null?

  - by Trimack

  Hi, I want to make a dictionary out of list in a way, that the list becomes keys and values would be empty. I have following code Dictionary<XmlTest, int?> testBattery = new XmlTests().GetRandomTestBattery(id). ToDictionary(k => k, v => null); But I am getting the error "Cannot convert lambda expression to type System.Collections.Generic.IEqualityComparer' because it is not a delegate type" Any ideas how could I fix it? (I know I could iterate through and fill the dict one element at a time, but I simply want to use something more elegant)

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• What is the best way to set default values in ActiveRecord?

  - by ryw

  What is the best way to set default value in ActiveRecord? I see a post from Pratik that describes an ugly, complicated chunk of code: http://m.onkey.org/2007/7/24/how-to-set-default-values-in-your-model class Item < ActiveRecord::Base def initialize_with_defaults(attrs = nil, &block) initialize_without_defaults(attrs) do setter = lambda { |key, value| self.send("#{key.to_s}=", value) unless !attrs.nil? && attrs.keys.map(&:to_s).include?(key.to_s) } setter.call('scheduler_type', 'hotseat') yield self if block_given? end end alias_method_chain :initialize, :defaults end YUCK! I have seen the following examples googling around: def initialize super self.status = ACTIVE unless self.status end and def after_initialize return unless new_record? self.status = ACTIVE end I've also seen people put it in their migration, but I'd rather see it defined in the model code. What's the best way to set default value for fields in ActiveRecord model?

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• Semantic errors

  - by gautam kumar

  Can semantic errors be detected by the compiler or not? If not when do the errors get detected? As far as I know semantic errors are those errors which result from the expressions involving operators with incorrect number/type of operands. For example: n3=n1*n2;//n1 is integer, n2 is a string, n3 is an integer The above statement is semantically incorrect. But while reading C Primer Plus by Stephen Prata I found the following statement The compiler does not detect semantic errors, because they don't violate C rules. The compiler has no way of divining your true intentions. That leaves it to you to find these kinds of errors. One way is to compare what a program does to what you expected it to do. If not the compiler, who detects those errors? Am I missing something?

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• What are the other new features of C# 4.0, after dynamic and optional parameters?

  - by Abel

  So, C# 4.0 came out yesterday. It introduced the much-debated dynamic keyword, named and optional parameters. Smaller improvements were the implicit ref and recognizing of indexed and default properties on COM methods, contra- and co-variance (really a .NET CLR feature, not C# only) and... Is that really it? Are dynamic and optional/named params the only real improvements to C#? Or did I miss something? Not that I'm complaining, but it seems a bit meager after C# 2.0 (generics) and C# 3.0 (lambda, LINQ). Maybe the language just reached actual maturity?

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• Linq To SQL: Retain list order when using .Contains

  - by rockinthesixstring

  I'm using Lucene.net to build a MyListOfIds As List(Of Integer) which I then pass on to my Linq service. I then search the database as follows Return _EventRepository.Read().Where(Function(e) MyListOfIds.Contains(e.ID)).ToList Now I know that Lucene is already ordering MyListOfIds based on the weight it gave each term. What sucks is that Linq is losing that order in it's SQL search. My Question: How can I retain that sort order when building my Lambda expression? I tried using LINQPad to see how the query is being built, but because I had to declare a variable LINQPad didn't show me the resultant SQL :-( Here's what I tried in LINQPad Dim i As New List(Of Integer) i.Add(1) i.Add(100) i.Add(15) i.Add(3) i.Add(123) Dim r = (From e In Events Where i.Contains(e.ID) Select e) note: my example is in VB.NET, but I don't mind if responses are in C#

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• Facebook API - Get comments

  - by Simon R

  Our business has a Facebook Fan Page. The fan page doesn't seem to generate any emails to us when updates are made to the page, whether someone adds a new status or someone comments on one of the statuses etc. Currently, we are running a very crude script to grab the content of the page and then use regular expressions to get the information we require. Obviously this is not fool proof and I'm looking into alternatives to this method. I've been looking at the facebook API and wonder if the rest server might be an option. I cannot, however, seem to find out how to return information of fan page statuses and their comments. Is anyone able to direct me how to use the API to retrieve this information. I am an admin of the fan page. The programming language I'm using is PHP. Many thanks.

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• Searching for simple variable names like 'c' or 'x' in Emacs.

  - by wpeters

  I often wish to search for variables that are simply called 'c' or 'count'. For example int c, count; Unfortunately when I use an incremental search for 'c' or 'count' I get a lot of unnecessary hits like the 'c' in 'choice', or the 'count' in 'wordcount' which do not interest me. I know Emacs can do i-searches with regular expressions but I don't know the correct regular expression needed to match just 'c' and 'count'. These words are often surrounded by any number of white spaces. Anyone know the regex I can use to narrow my search?

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• Replacing elements within a string in R

  - by Maureen

  Hi, I have a row in a data frame in R that is made up of sequences of undetermined length of 0s 1s and 2s as characters. So "01", "010", "201", "102", "00012"... things like this. I'd like to find a way to determine if the last character in the string is NUMERICALLY the largest. It's important that I keep the row in the data frame as characters for other purposes. So basically I want to take substr(x, nchar(x), nchar(x)) and determine if it, as a number, is the largest of the numbers in the character string. I'm super lost as to how to do this, since I'm not all that familiar with regular expressions and I have to back and forth between treating elements as characters and numbers. Thanks in advance. ~Maureen

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• Safely dereferencing FirstOrDefault call in Linq c#

  - by samy

  For brevity's sake in my code, i'd like to be able to do the following: having a collection, find the first element matching a lambda expression; if it exists, return the value of a property or function. If it doesn't exist, return null. var stuff = {"I", "am", "many", "strings", "obviously"}; var UpperValueOfAString = stuff.FirstOrDefault(s => s.contains("bvi")).ToUpper(); // would return "OBVIOUSLY" var UpperValueOfAStringWannabe = stuff.FirstOrDefault(s => s.contains("unknown token")).ToUpper(); // would return null Is it possible with some linq-syntax-fu or do i have to check explicitly for the return value before proceeding?

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• Complex regular expression

  - by Jose3d

  Hello, i will like to capture a substring part of a text choosing the number of characters but if any word is cut then get until de last blank. As example if this is the text: "This is an example of text lorem ipsum, etc..." and i would like to get for instance 12 characters that are: "This is an e". In this case example is cutted, then i would like to get "This is an". Its possible do this with Regular Expressions? Thanks in advance. Jose

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• What should I know about Python to identify comments in different source files?

  - by Can't Tell

  I have a need to identify comments in different kinds of source files in a given directory. ( For example java,XML, JavaScript, bash). I have decided to do this using Python (as an attempt to learn Python). The questions I have are 1) What should I know about python to get this done? ( I have an idea that Regular Expressions will be useful but are there alternatives/other modules that will be useful? Libraries that I can use to get this done?) 2) Is Python a good choice for such a task? Will some other language make this easier to accomplish?

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• GUID.TryParse() ?

  - by Jack Marchetti

  Obviously there is no public GUID.TryParse() in .NET CLR 2.0. So, I was looking into regular expressions [aka googling around to find one] and each time I found one there was a heated argument in the comments section about RegEx A doesn't work, use RegEx B. Then someone would write Regex C yadda yadda So anyway, What I decided to do was this, but I feel bad about it. public static bool IsGuid (string possibleGuid) { try { Guid gid = new Guid(possibleGuid); return true; } catch (Exception ex) { return false; } } Obviously I don't really like this since it's been drilled into me since day one to avoid throwing exceptions if you can defensibly code around it. Does anyonek now why there is no public Guid.TryParse() in the .NET Framework? Does anyone have a real Regular Expression that will work for all GUIDs?

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• Vb.Net action delegate problem?

  - by Ramesh Vel

  Hi, Am vb.net newbie. This question might be very novice and answered before, but i couldn't find. I was trying the lambda features and got struck here. Private Function HigerOrderTest(highFunction as Func(Of Int16,Int16)) As Action(of String) Dim sam = highFunction(3) Dim DoIt as Action(of String) DoIt = sub(s) console.WriteLine(s) return DoIt End Function I got "Expression expected." at line DoIt = sub(s) console.WriteLine(s). And when i changed this to DoIt = function(s) console.WriteLine(s) i got Expression does not produce a value. error. Whats the problem? Cheers

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• Adding items to dictionary if condition is true, else dont - python

  - by CodeTalk

  I'm trying to take an existing process: if self.path_object is not None: dictpath = {} for path in self.path_object: self.params = path.pathval.split("?")[0] self.params = path.pathval.split("&", 2) if path.pathval.contains(self.params): out = list(map(lambda v: v.split("=")[0] +"=" + str(self.fuzz_vectors), self.params)) else: pass dictpath[path] = out print dictpath I added the sub-if/else block in, but it is failing, stating: AttributeError: 'unicode' object has no attribute 'contains' on the if block . How can I fix it? I'm simply trying to do: if the path.pathval has either ? or & in it: add to dictionary else: pass #forget about it. Thanks!

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• Efficient way to organise data file in columns with Python

  - by user1700959

  I'm getting an output data file of a program which looks like this, with more than one line for each time step: 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 7.9819E-06 1.7724E-02 2.3383E-02 3.0048E-02 3.8603E-02 4.9581E-02 5.6635E-02 4.9991E-02 3.9052E-02 3.0399E-02 .... I want to arrange it in ten columns I have made a Python script, using regular expressions to delete \n in the proper lines, but I think that there should be a simpler more elegant way to do it, here is my script: import re with open('inputfile', encoding='utf-8') as file1: datai=file1.read() dataf=re.sub(r'(?P<nomb>( \d\.\d\d\d\dE.\d\d){8})\n','\g<nomb>',datai) with open('result.txt',mode='w',encoding='utf-8') as resultfile: resultfile.write(datof) Thanks in advance

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• Java String replaceAll with conditions

  - by user1483570

  I am not good in regular expressions and I need help in replacing the string. String str = "Name_XYZ_"; str = "XYZ_NAME_"; So how can I replace "Name_" or "_NAME_" from above two strings with empty string? The conditions are "Name" can be in any case and it can be at index 0 or at any index but preceded by "_". So far I tried, String replacedString = str.replaceAll("(?i)Name_", ""); // This is not correct. This is not the homework. I am working on XML file that needs such kind of processing. Please help. Thank you.

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• deploying a war to tomcat using python

  - by Decado

  Hi, I'm trying to deploy a war to a Apache Tomcat server (Build 6.0.24) using python (2.4.2) as part of a build process. I'm using the following code import urllib2 import base64 war_file_contents = open('war_file.war','rb').read() username='some_user' password='some_pwd' base64string = base64.encodestring('%s:%s' % (username, password))[:-1] authheader = "Basic %s" % base64string opener = urllib2.build_opener(urllib2.HTTPHandler) request = urllib2.Request('http://158.155.40.110:8080/manager/deploy?path=war_file', data=war_file_contents) request.add_header('Content-Type', 'application/octet-stream') request.add_header("Authorization", authheader) request.get_method = lambda: 'PUT' url = opener.open(request) the url.code is 200, and the url.msg is "OK". However the web archive doesn't appear on the manager list applications page. Thanks.

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• What is the best regular expression for validating email addresses?

  - by acrosman

  Over the years I have slowly developed a regular expression that validates MOST email addresses correctly, assuming they don't use an IP address as the server part. Currently the expression is: ^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,4})$ I use this in several PHP programs, and it works most of the time. However, from time to time I get contacted by someone that is having trouble with a site that uses it, and I end up having to make some adjustment (most recently I realized that I wasn't allowing 4-character TLDs). What's the best regular expression you have or have seen for validating emails? I've seen several solutions that use functions that use several shorter expressions, but I'd rather have one long complex expression in a simple function instead of several short expression in a more complex function.

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• Storing expression template functors

  - by UncaughtException

  Hello guys, at the moment I'm really interested in expression templates and want to code a library for writing and differentiating mathematical functions with a lambda-style syntax. At the moment, I'm able to write (_x * _x)(2); and get the correct result 4. But I would really like to do something like MathFunction f = _x * _x; f(2);, but I don't have any ideas on how to cope with the recursive expression templates on the right side. Is it possible to achieve this without using the 'auto'-Keyword instead of MathFunction or having to make the operator() virtual? Thanks for your help!

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• How do I bind a key to "the function represented by the following key sequence"?

  - by katrielalex

  I'm just starting to learn emacs (woohoo!) and I've been mucking around in my .emacs quite happily. Unfortunately, I don't know Lisp yet, so I'm having issues with the basics. I've already remapped a few keys until I fix my muscle memory: (global-set-key (kbd "<f9>") 'recompile) That's fine. But how can I tell a key to 'simulate pressing several keys'? For instance, I don't know, make <f1> do the same as C-u 2 C-x } (widen buffer by two chars). One way is to look up that C-x } calls shrink-window-horizontally, and do some sort of lambda thing. This is of course the neat and elegant way (how do you do this?). But surely there's a way to define <f1> to send the keystrokes C-u 2 C-x }?

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• Is it possible to "learn" a regular expression by user-provided examples?

  - by DR

  Is it possible to "learn" a regular expression by user-provided examples? To clarify: I do not want to learn regular expressions. I want to create a program which "learns" a regular expression from examples which are interactively provided by a user, perhaps by selecting parts from a text or selecting begin or end markers. Is it possible? Are there algorithms, keywords, etc. which I can Google for? EDIT: Thank you for the answers, but I'm not interested in tools which provide this feature. I'm looking for theoretical information, like papers, tutorials, source code, names of algorithms, so I can create something for myself.

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