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• Does replacing statements by expressions using the C++ comma operator could allow more compiler opti

  - by Gabriel Cuvillier

  The C++ comma operator is used to chain individual expressions, yielding the value of the last executed expression as the result. For example the skeleton code (6 statements, 6 expressions): step1; step2; if (condition) step3; return step4; else return step5; May be rewritten to: (1 statement, 6 expressions) return step1, step2, condition? step3, step4 : step5; I noticed that it is not possible to perform step-by-step debugging of such code, as the expression chain seems to be executed as a whole. Does it means that the compiler is able to perform special optimizations which are not possible with the traditional statement approach (specially if the steps are const or inline)? Note: I'm not talking about the coding style merit of that way of expressing sequence of expressions! Just about the possible optimisations allowed by replacing statements by expressions.

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• XPath filter not empty attribute

  - by Marcos Buarque

  Hi, I need to filter a XPath expression to grab only a certain attribute as not empty. I tried this: <xsl:template match="DocumentElement/QueryResults[string(@FileName)]"> and this: <xsl:template match="DocumentElement/QueryResults[string-length(@FileName)>0]"> but it did not work. I need the same kind of data returning from the folloing XPath expression... <xsl:template match="DocumentElement/QueryResults"> ... but filtered to avoid items with empty attribute @FileName. Thanks!

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• Can I mix compile time string comparison with MPL templates?

  - by Negative Zero

  I got this compile time string comparison from another thread using constexpr and C++11 (http://stackoverflow.com/questions/5721813/compile-time-assert-for-string-equality). It works with constant strings like "OK" constexpr bool isequal(char const *one, char const *two) { return (*one && *two) ? (*one == *two && isequal(one + 1, two + 1)) : (!*one && !*two); } I am trying to use it in the following context: static_assert(isequal(boost::mpl::c_str<boost::mpl::string<'ak'>>::value, "ak"), "should not fail"); But it gives me an compilation error of static_assert expression is not an constant integral expression. Can I do this?

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• Get positions for NAs only in the "middle" of a matrix column

  - by Abiel

  I want to obtain an index that refers to the positions of NA values in a matrix where the index is true if a given cell is NA and there is at least one non-NA value before and after it in the column. For example, given the following matrix [,1] [,2] [,3] [,4] [1,] NA 1 NA 1 [2,] 1 NA NA 2 [3,] NA 2 NA 3 the only value of the index that comes back TRUE should be [2,2]. Is there a compact expression for what I want to do? If I had to I could loop through columns and use something like min(which(!is.na(x[,i]))) to find the first non-NA value in each column, and then set all values before that to FALSE (and the same for all values after the max). This way I would not select leading and trailing NA values. But this seems a bit messy, so I'm wondering if there is a cleaner expression that does this without loops.

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• .NET C# setting the value of a field defined by a lambda selector

  - by Frank Michael Kraft

  I have a generic class HierarchicalBusinessObject. In the constructor of the class I pass a lambda expression that defines a selector to a field of TModel. protected HierarchicalBusinessObject (Expression<Func<TModel,string>> parentSelector) A call would look like this, for example: public class WorkitemBusinessObject : HierarchicalBusinessObject<Workitem,WorkitemDataContext> { public WorkitemBusinessObject() : base(w => w.SuperWorkitem, w => w.TopLevel == true) { } } I am able to use the selector for read within the class. For example: sourceList.Select(_parentSelector.Compile()).Where(... Now I am asking myself how I could use the selector to set a value to the field. Something like selector.Body() .... Field...

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• How to initialize F# list when size is unknown, using while..do loop

  - by James Black

  I have a function that will parse the results of a DataReader, and I don't know how many items are returned, so I want to use a while..do loop to iterate over the reader, and the outcome should be a list of a certain type. (fun(reader) -> [ while reader.Read() do new CityType(Id=(reader.GetInt32 0), Name=(reader.GetString 1), StateName=(reader.GetString 2)) ]) This is what I tried, but the warning I get is: This expression should have type 'unit', but has type 'CityType'. Use 'ignore' to discard the result of the expression, or 'let' to bind the result to a name. So what is the best way to iterate over a DataReader and create a list?

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• Interning strings in Java

  - by Tiny

  The following segment of code interns a string. String str1="my"; String str2="string"; String concat1=str1+str2; concat1.intern(); System.out.println(concat1=="mystring"); The expression concat1=="mystring" returns true because concat1 has been interned. If the given string mystring is changed to string as shown in the following snippet. String str11="str"; String str12="ing"; String concat11=str11+str12; concat11.intern(); System.out.println(concat11=="string"); The comparison expression concat11=="string" returns false. The string held by concat11 doesn't seem to be interned. What am I overlooking here? I have tested on Java 7, update 11.

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• How can I convert Perl regular expressions to boost regular expressions?

  - by YY

  I'm not familiar with Perl and boost regular expression and I want to convert a Perl code to c++. I want to convert special regular expression in Perl into c++ using Boost regexp library. Please help me understand what I must do? Here is some regexps that a word of a sentence may match: if ($word =~ /^[\.:\,()\'\`-]/) { # hack for punctuation } if ($word =~ /^[A-Z]/) { return; } if ($word =~ /[A-Za-z0-9]+\-[A-Za-z0-9]+/) { # all hyphenated words return; } if ($word =~ /.*[0-9].*/) { # all numbers return; }

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• how to use expressons as function parameters in powershell

  - by rmeador

  This is a very simple task in every language I have ever used, but I can't seem to figure it out in PowerShell. An example of what I'm talking about in C: abs(x + y) The expression x + y is evaluated, and the result passed to abs as the parameter... how do I do that in PowerShell? The only way I have figured out so far is to create a temporary variable to store the result of the expression, and pass that. PowerShell seems to have very strange grammar and parsing rules that are constantly catching me by surprise, just like this situation. Does anyone know of documentation or a tutorial that explains the basic underlying theory of the language? I can't believe these are all special cases, there must be some rhyme or reason that no tutorial I have yet read explains. And yes, I've read this question, and all of those tutorials are awful. I've pretty much been relegated to learning from existing code.

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• Build a decision tree for classification of large amount data,using python?

  - by kaushik

  Hi,i am working for speech synthesis.In this i have a large number of pronunciation for each phone i.e alphabet and need to classify them according to few feature such as segment size(int) and alphabet itself(string) into a smaller set suitable for that particular context. For this purpose,i have decided to use decision tree for classification.the data to be parsed is in the S expression format.eg:((question)(LEFTNODE)(RIGHTNODE)). i hav idea for building decision tree for normal buit in type such as list..looking for suggestion for implementation for S expression.. kindly help.. Thanks in advance.. Note:this question may look similar to my prev post,srry if cant giv multiple post.already edited it many times so though of wirting new question instead of editing again

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• Problem with do construct in haskell

  - by Anonymous Coward

  Hello everyone I'm trying to learn Haskell and want to write a small program which prints the content of a file to the screen. When I load it into GHCi I get the following error: The last statement in a 'do' construct must be an expression I know this question has be asked already here: Haskell — “The last statement in a 'do' construct must be an expression”. Even though my code is very similar I still can't figure out the problem. If anyone could point out the problem to me I'd be very thankful. module Main (main) where import System.IO import System(getArgs) main :: IO() main = do args <- getArgs inh <- openFile $ ReadMode head args printFile inh hClose inh printFile :: Handle -> IO () printFile handle = do end <- hIsEOF handle if end then return () else do line <- hGetLine handle putStrLn line printFile handle

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• Linq Query Giving Error

  - by user275561

  I am getting this error when I use the Linq expression of var emp = _testModel.Where(m => m.Date == DateTime.Now).Select(m=>m); 'System.Collections.Generic.IEnumerable' does not contain a definition for 'System' and no extension method 'System' accepting a first argument of type 'System.Collections.Generic.IEnumerable' could be found (are you missing a using directive or an assembly reference?). I have google'd and looked everywhere by I have no idea what it is talking about? It doesn't throw an exception. The only way I found out about this was stepping through the expression.

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• Python __setattr__ and __getattr__ for global scope?

  - by KT

  Suppose I need to create my own small DSL that would use Python to describe a certain data structure. E.g. I'd like to be able to write something like f(x) = some_stuff(a,b,c) and have Python, instead of complaining about undeclared identifiers or attempting to invoke the function some_stuff, convert it to a literal expression for my further convenience. It is possible to get a reasonable approximation to this by creating a class with properly redefined __getattr__ and __setattr__ methods and use it as follows: e = Expression() e.f[e.x] = e.some_stuff(e.a, e.b, e.c) It would be cool though, if it were possible to get rid of the annoying "e." prefixes and maybe even avoid the use of []. So I was wondering, is it possible to somehow temporarily "redefine" global name lookups and assignments? On a related note, maybe there are good packages for easily achieving such "quoting" functionality for Python expressions?

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• Converting ObjC Blocks to C# Lambas

  - by Sam

  I need some help converting an Objective-C block to C#. Here is the source ObjC: NSDate* addYear = [_calendar dateByAddingComponents:((^{ NSDateComponents* components = [NSDateComponents new]; components.month = 12; return components; })()) toDate:now options:0]; Now I tried the following in C#: NSDate date = _calendar.DateByAddingComponents((() => { NSDateComponents components = new NSDateComponents(); components.Month = 12; return components; })(), now, NSCalendarOptions.None); To which I get the following compiler error: Expression denotes a 'anonymous method' where a 'method group' was expected. Removing the parentheses around the lambda yields Cannot convert 'lambda expression' to non-delegate type 'MonoTouch.Foundation.NSDateComponents'. What is the correct C# syntax? I need to retain the closures as there are a lot more in the code base that I am porting.

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• Collectable<T> serialization, Root Namespaces on T in .xml files.

  - by Stacey

  I have a Repository Class with the following method... public T Single<T>(Predicate<T> expression) { using (var list = (Models.Collectable<T>)System.Xml.Serializer.Deserialize(typeof(Models.Collectable<T>), FileName)) { return list.Find(expression); } } Where Collectable is defined.. [Serializable] public class Collectable<T> : List<T>, IDisposable { public Collectable() { } public void Dispose() { } } And an Item that uses it is defined.. [Serializable] [System.Xml.Serialization.XmlRoot("Titles")] public partial class Titles : Collectable<Title> { } The problem is when I call the method, it expects "Collectable" to be the XmlRoot, but the XmlRoot is "Titles" (all of object Title). I have several classes that are collected in .xml files like this, but it seems pointless to rewrite the basic methods for loading each up when the generic accessors do it - but how can I enforce the proper root name for each file without hard coding methods for each one? The [System.Xml.Serialization.XmlRoot] seems to be ignored.

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• Why does concatenating strings in the argument of EXEC sometimes cause a syntax error in T-SQL?

  - by Tim Goodman

  In MS SQL Server Management Studio 2005, running this code EXEC('SELECT * FROM employees WHERE employeeID = ' + CAST(3 AS VARCHAR)) gives this error: Incorrect syntax near 'CAST' However, if I do this, it works: DECLARE @temp VARCHAR(4000) SET @temp = 'SELECT * FROM employees WHERE employeeID = ' + CAST(3 AS VARCHAR) EXEC(@temp) I found an explanation here: http://stackoverflow.com/questions/1044831/t-sql-cannot-pass-concatenated-string-as-argument-to-stored-procedure According to the accepted answer, EXEC can take a local variable or a value as its argument, but not an expression. However, if that's the case, why does this work: DECLARE @temp VARCHAR(4000) SET @temp = CAST(3 AS VARCHAR) EXEC('SELECT * FROM employees WHERE employeeID = ' + @temp) 'SELECT * FROM employees WHERE employeeID = ' + @temp sure looks like an expression to me, but the code executes with no errors.

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• SQL Server Reporting Services Format Hours as Hours:Minutes

  - by Frank Schmitt

  I'm writing reports on SQL Server Reporting Server that have a number of hours grouped by, say, user, and a total calculated based on the sum of the values. Currently my query runs a stored proc that returns the hours as in HH:MM format, rather than decimal hours, as our users find that more intuitive. The problem occurs when I try and add up the column using an SSRS expression, because the SUM function isn't smart enough to handle adding up times in this format. Is there any way to: Display a time interval (in minutes or hours) in HH:MM format while having it calculated in decimal form? Or split up and calculate the total of the HH:MM text values to arrive at a total as an expression? I'd like to avoid having to write/run a second query just to get the total.

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• How can i pass a single additional argument to array_map callback in PHP?

  - by Gremo

  How can i pass a single additional argument to array_map callback? In my example i'd like to pass $smsPattern (as a second argument, after current element in $featureNames) to the function array_map with $getLimit closure: $features = $usage->getSubscription()->getUser()->getRoles(); // SMS regular expression in the form of ROLE_SEND_SMS_X $smsPattern = '/^ROLE_SEND_SMS_(?P<l>\d+)$/i'; // Function to get roles names and X from a role name $getNames = function($r) { return trim($r->getRole()); }; $getLimit = function($name, $pattern) { if(preg_match($pattern, $name, $m)) return $m['l']; }; // Get roles names and their limits ignoring null values with array_filter $featuresNames = array_map($getNames, $features); $smsLimits = array_filter(array_map($getLimit, $featureNames, $smsPattern)); With this code i'm getting a weird warning: Warning: array_map() [function.array-map]: Argument #3 should be an array. Of course di reason is for reusing $getLimit closure with another regular expression like $smsPattern. Thanks.

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• validate a string for text ,operators and ( [ ]) brackets

  - by sarah

  Hi, i want a regular expression to validate string to have only text,operators and these brackets ([ ])

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• C++ vector and segmentation faults

  - by Headspin

  I am working on a simple mathematical parser. Something that just reads number = 1 + 2; I have a vector containing these tokens. They store a type and string value of the character. I am trying to step through the vector to build an AST of these tokens, and I keep getting segmentation faults, even when I am under the impression my code should prevent this from happening. Here is the bit of code that builds the AST: struct ASTGen { const vector<Token> &Tokens; unsigned int size, pointer; ASTGen(const vector<Token> &t) : Tokens(t), pointer(0) { size = Tokens.size() - 1; } unsigned int next() { return pointer + 1; } Node* Statement() { if(next() <= size) { switch(Tokens[next()].type) { case EQUALS : Node* n = Assignment_Expr(); return n; } } advance(); } void advance() { if(next() <= size) ++pointer; } Node* Assignment_Expr() { Node* lnode = new Node(Tokens[pointer], NULL, NULL); advance(); Node* n = new Node(Tokens[pointer], lnode, Expression()); return n; } Node* Expression() { if(next() <= size) { advance(); if(Tokens[next()].type == SEMICOLON) { Node* n = new Node(Tokens[pointer], NULL, NULL); return n; } if(Tokens[next()].type == PLUS) { Node* lnode = new Node(Tokens[pointer], NULL, NULL); advance(); Node* n = new Node(Tokens[pointer], lnode, Expression()); return n; } } } }; ... ASTGen AST(Tokens); Node* Tree = AST.Statement(); cout << Tree->Right->Data.svalue << endl; I can access Tree->Data.svalue and get the = Node's token info, so I know that node is getting spawned, and I can also get Tree->Left->Data.svalue and get the variable to the left of the = I have re-written it many times trying out different methods for stepping through the vector, but I always get a segmentation fault when I try to access the = right node (which should be the + node) Any help would be greatly appreciated.

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• No-argument method on window.external is invoked when checking with typeof

  - by janko

  Hi, I am trying to display an HTML page with embedded JavaScript code inside a System.Windows.Forms.WebBrowser control. The JavaScript code is expected to interact with the embedding environment through the window.external object. Before invoking a method on window.external, JavaScript is supposed to check for the existance of the method. If it is not there, the code should invoke a generic fallback method. // basic idea if (typeof(window.external.MyMethod) != 'undefined') { window.external.MyMethod(args); } else { window.external.Generic("MyMethod", args); } However, checking for a no-argument method with typeof seems to invoke the method already. That is, if MyMethod accepts any positive number of arguments, the code above will work perfectly; but, if MyMethod is a no-argument method, then the expression typeof(window.external.MyMethod) will not check for its type but invoke it, too. Is there any work-around to this behavior? Can I somehow escape the expression window.external.MyMethod to prevent the method call from occurring?

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• Perl : How to get All grouped patterns

  - by pavun_cool

  I have this following code. Here I am matching the vowels characters words if ( /(a)+/ and /(e)+/ and /(i)+/ and /(o)+/ and /(u)+/ ) { print "$1#$2#$3#$4#$5\n"; $number++; } I am trying to get the all matched patterns using grouping . But I am getting only last expression pattern , which means fifth expression of if condition . Here I know that it is giving only one pattern because last pattern matching in if condition. But I want to get all matched patterns Any one help me out of this problem.

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• How to make validation for a textbox that accept only comma(,) & digit in c# web application?

  - by prateeksaluja20

  Hello Experts, I am working on a website.I am using C# 2008.I want to make a text box that accept only numbers & comma(,). for example-919981424199,78848817711,47171111747 or there may be a single number like 919981424199. I was able to do one thing My text box only containing number by using this Regular Expression validation.in its property-Validation Expression i wrote "[0-9]+". This is working but now my requirement is to send bulk SMS & each number is separated by (,). I tried a lot but not getting the ans.so please help me to sort out this problem. Thanks in advance.

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• Lookup function not working (RS SP2)

  - by Al Reyes

  Hi, I made the upgrade to SP2. I'm trying to use the Lookup function to link data from two different servers. I'm trying first a simple exercise linking data from two datasets from the same server, having one dataset with journals and the other with the account description. My Expression looks like this at a field on the table I have: =Lookup(Fields!ACTINDX.Value,Fields!ACTINDX.Value,Fields!ACTDESCR.Value,"ACCTINFO") I made sure of the names and using only uppercases for datasets and fields but I'm receiving the following message when I try to preview: "An error occurred during local report processing. The definition of the report '/DETAIL' is invalid. The Value expression for the text box 'ACTINDX' refers to the field 'ACTDESCR'. Report item expressions can only refer to fields within the current dataset scope or, if inside an aggregate, the specified dataset scope". I'll appreciate any suggestions. Regards, Al

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• Winform .Net 3.5 - Get path of ApplicationFolder for Office Add-In

  - by Serexx

  Greetings - I am writing an add-in for Expression Web 3 in VS2008 The solution has a Windows Installer setup project in which the ApplicationFolder is tagged to hold some ancillary files. I need to be able to access those files during the add-in's startup, but naturally the Application object as well as the AppDomain reference paths to Expression Web not to the Add-In. There is a tickle in the back of my head that the solution involves reflection but thats as far as I can get... has anyone dealt with this or have any suggestions? Thanks!

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