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• How do I perform a dynamic select in Linq?

  - by Matt Mangold

  I am trying to figure out how to dynamically specify the properties for my select clause in a linq query. Lets say I have a collection of employee objects. At run time, the end user will be specifying which properties they would like to see for those employees, so I need to be able to dynamically construct my Linq select clause. I have used the dynamic Linq library, but I prefer not to use that, because it requires me to build a string to pass to the select method. I'd like to understand how to do this via Expressions.

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• Does C++ require a destructor call for each placement new?

  - by Josh Haberman

  I understand that placement new calls are usually matched with explicit calls to the destructor. My question is: if I have no need for a destructor (no code to put there, and no member variables that have destructors) can I safely skip the explicit destructor call? Here is my use case: I want to write C++ bindings for a C API. In the C API many objects are accessible only by pointer. Instead of creating a wrapper object that contains a single pointer (which is wasteful and semantically confusing). I want to use placement new to construct an object at the address of the C object. The C++ object will do nothing in its constructor or destructor, and its methods will do nothing but delegate to the C methods. The C++ object will contain no virtual methods. I have two parts to this question. Is there any reason why this idea will not work in practice on any production compiler? Does this technically violate the C++ language spec?

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• Push a variable into global scope?

  - by Spot

  We use instantiate and put system critical objects in $GLOBALS for easy access from anywhere (e.g. DB, Cache, User, etc.). We use $GLOBALS so much that it would (yes, really) drop the amount of code quite a bit if I could reference it like $G = &$GLOBALS for a shorthand call. The problem is that, per my experience and several hours of Googling, I have not found any construct in PHP which allows you to 'flag' a var as global, making $GLOBALS first class, and everything else second class. Am I missing something? Is this possible?

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• Why isn't my IO executed in order?

  - by HaskellElephant

  Hi, I'm having some fun learning about the haskell IO. However in my recent exploration of it I have encountered some problems with IO not executing in order, even inside a do construct. In the following code I am just keeping track of what cards are left, where the card is a tuple of chars (one for suit and one for value) then the user is continously asked for wich cards have been played. I want the putStr to be executed between each input, and not at the very end like it is now. module Main where main = doLoop cards doLoop xs = do putStr $ show xs s <- getChar n <- getChar doLoop $ remove (s,n) xs suits = "SCDH" vals = "A23456789JQK" cards = [(s,n) | s <- suits, n <- vals] type Card = (Char,Char) remove :: Card -> [Card] -> [Card] remove card xs = filter (/= card) xs

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• Nhibernate and not-exists query

  - by Dan

  I'm trying to construct a query in NHibernate to return a list of customers with no orders matching a specific criteria. My Customer object contains a set of Orders: <set name="Orders"> <key column="CustomerID" /> <one-to-many class="Order" /> </set> How do I contruct a query using NHibernate's ICriteria API to get a list of all customers who have no orders? Using native SQL, I am able to represent the query like this: select * from tblCustomers c where not exists (select 1 from tblOrders o where c.ID = o.CustomerID) I have been unable to figure out how to do this using aliases and DetatchedCriteria objects. Any guidance would be appreciated! Thanks!

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• static effect on python

  - by fatai

  how we can construct static effect on python instead of using class and global ? not like that one : global a a = [] #simple ex ; fonk ( a , b , d) x = 1 a.append ( x) EDIT: I want to create temporary memory , if I exit the function namely fonk , I want to save change as list on temporary memory . We can do that demand only put static keyword in front of data type but in python , we dont have static, so I want that effect in python . Therefore , how can I do ? As above code say "a" represents temporary memory

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• Image processing custom filter 7 by 7

  - by ladiesMan217

  Lets say I have a 7 by 7 neighborhood around a pixel that looks like this 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 and I wanna filter the above by replacing the pixel p by the average of those pixels whose value lie in the range -10<=p_value <=10. I am new to image processing and I think in this case p_value is 25 and around 25 that are many pixel values in that range but don't exactly know to construct a convolution filter out of it.

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• Is it possible to creating a Service without starting it?

  - by ThaMe90

  Hello all, I wonder, is it possible to create a Service, set some data, and then start it? I haven't come across a thread specific to this problem, so I would like to know if it is possible (if it is known of course). My problem is that I have a Service which listens to a DatagramSocket, but the socket in question needs to be set after creation, but before the start of the Service. The setting of the socket happens through the use of a Broadcast (I broadcast 2 Strings which hold the IP-Address & Port and the BroadcastReceiver then constructs a socket for me). When the Service is started, a Thread will start to run and listen to the supposedly created socket. This, sadly, doesn't happen. The socket will remain null and I can't set it when the Thread is running (This is another issue I hope to tackle in the future, if anybody got any ideas about this, please notify me). So, is what I want possible, or should I come up with another construct for achieving this goal?

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• 3D framework/library os x

  - by Deano

  Does anyone have any advice as to a good framework for simplifying the generation of 3D models? I am trying to construct a parametric program for tasks such as ship design. Actions such as surface modelling, intersections etc are a must. I have investigated openCASCADE and it shows promise but getting it to integrate into a native cocoa interface is not currently achievable (By me at any rate). All ideas and suggestions welcome. Should I just forget it and integrate an X11 window, if so any tutorials for doing this?

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• Preventing a security breach

  - by Wiz

  I am creating a website where you "post", and the form content is saved in a MySql database, and upon loading the page, is retrieved, similar to facebook. I construct all the posts and insert raw html into a template. The thing is, as I was testing, I noticed that I could write javascript or other HTML into the form and submit it, and upon reloading, the html or JS would treated as source code, not a post. I figured that some simple encoding would do the trick, but using is not working. Is there an efficient way to prevent this type of security hole?

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• whats wrong with this piece of code for saving contacts

  - by Shadow

  Hi, i am using the latest Nokia Qt SDK. i have tried to add the contacts, its not getting added.. what is missing here.. // Construct contact manager for default contact backend QContactManager* cm = new QContactManager("simulator"); // QContactManager* cm = new QContactManager("memory"); // i tried this, its also not working // Create example contact QContact example; // Add contact name QContactName name; name.setFirstName("John"); name.setLastName("Doe"); example.saveDetail(&name); // Add contact email address //QContactEmailAddress email; // email.setContexts(QContactDetail::ContextHome); //email.setEmailAddress(“[email protected]”); // example.saveDetail(&email); // Finally, save the contact details cm->saveContact(&example); delete cm; Thanks

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• XPath 1.0 to find if an element's value is in a list of values

  - by user364902

  Is there a way to construct an XPath that evaluates whether an element's value is in a predefined list of values? Something akin to this: /Location/Addr[State='TX or AL or MA'] Which would match nodes whith State elements for Texas, Alabama, or Massachusetts? I know that I can unpack the expression: /Location/Addr[State='TX] or /Location/Addr[State='AL'], etc... But this is a bit cumbersome since the xpaths are quite long, as is the list of values. My google-fu isn't turning up much on the issue...

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• Get count matches in query on large table very slow

  - by Roy Roes

  I have a mysql table "items" with 2 integer fields: seid and tiid The table has about 35000000 records, so it's very large. seid tiid ----------- 1 1 2 2 2 3 2 4 3 4 4 1 4 2 The table has a primary key on both fields, an index on seid and an index on tiid. Someone types in 1 or more tiid values and now I would like to get the seid with most results. For example when someone types 1,2,3, I would like to get seid 2 and 4 as result. They both have 2 matches on the tiid values. My query so far: SELECT COUNT(*) as c, seid FROM items WHERE tiid IN (1,2,3) GROUP BY seid HAVING c = (SELECT COUNT(*) as c, seid FROM items WHERE tiid IN (1,2,3) GROUP BY seid ORDER BY c DESC LIMIT 1) But this query is extremly slow, because of the large table. Does anyone know how to construct a better query for this purpose?

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• How to add space after elements added via jQuery

  - by ahsteele

  I am rendering a similar construct to the below with some server side code. The server side code inserts hard returns in between the project label and text fields. Not a big deal except the below jQuery code inserts the project label and text fields mashed together. var projectLabel = $('<label for="project">Project</label>'); var projectField = $('<input type="text" name="project" id="projectName" />'); projectLabel.insertBefore($(this)); projectField.insertBefore($(this)); Because of this discrepancy the elements rendered server side have a space between them while the ones rendered on the client do not. I've tried adding a nbsp; at the end of each line to no avail. Unfortunately, I have been unable to remove the hard returns outputted by the server side code. Further because of the space I can't fix this with CSS. What are my options for adding spacing via jQuery?

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• How to create and Expression tree to do the same as "StartsWith"

  - by Jonathan

  Hi to all. Currently, I have this method to compare two numbers Private Function ETForGreaterThan(ByVal query As IQueryable(Of T), ByVal propertyValue As Object, ByVal propertyInfo As PropertyInfo) As IQueryable(Of T) Dim e As ParameterExpression = Expression.Parameter(GetType(T), "e") Dim m As MemberExpression = Expression.MakeMemberAccess(e, propertyInfo) Dim c As ConstantExpression = Expression.Constant(propertyValue, propertyValue.GetType()) Dim b As BinaryExpression = Expression.GreaterThan(m, c) Dim lambda As Expression(Of Func(Of T, Boolean)) = Expression.Lambda(Of Func(Of T, Boolean))(b, e) Return query.Where(lambda) End Function It works fine and is consumed in this way query = ETForGreaterThan(query, Value, propertyInfo) As you can see, I give it an IQueryable collection and it add a where clause to it, base on a property and a value. Y can construct Lessthan, LessOrEqualThan etc equivalents as Expression has this operators predefined. ¿How can I transform this code to do the same with strings? Expression don't give me a predefined operator like "contains" or "startwith" and I'm really noob with Expression trees. Thanks, and please Post your answer in C#/VB. Choose the one that make you feel more confortable.

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• XPath to compare two distinct attributes of two elements

  - by user364902

  Suppose I have this XML: <x> <e s="1" t="A"/> <e s="2" t="A"/> <e s="1" t="B"/> </x> Is there any way to write an xpath to find any nodes named "e" which have the same value of @s as another node but a different value of @t for the same node. The first part is easy: //e[@s = //e/@s] as is the second part: //e[@t != //e[@t]] But I don't see any way to construct an xpath that compares two different attributes for two separate elements "e". Is there a way within the xpath syntax, or is it hopeless?

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• SQL query help - merge a value to all rows in a column

  - by Tommy

  I'm trying to migrate a site from a joomla system to a drupal. The problem is that drupal needs filename and sourcepath in the same row, but joomla only has filename. I'm looking for a way to add sourcepath before the filename in all the rows in that column. I'm figuring it's the UPDATE statement that I should use, but I can't figure out how to construct the query. There's a person with a similar problem here, but I don't find the answers in that thread helpful to my problem: http://www.daniweb.com/forums/showth...t+value&page=2 Any suggestions?

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• HTML/Javascript: Is it possible to remember the filename from a fileupload field ONLY and then later

  - by Pieter Breed

  I have a HTML file upload field from which I'm reading the file name of the file that the user specifies. The actual contents of the file is never uploaded. At a later stage, is it possible to construct a link using this file name information so that if the user clicks on this link, the original file is launched into a new browser window? If not, what are the reason for disallowing this behaviour? The purpose of such a feature is to store links to documents that are available on a mapped local drive or a network share.

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• Sorting 2 arrays that have been added together

  - by tyler

  In my app, users can create galleries that their work may or may not be in. Users have and belong to many Galleries, and each gallery has a 'creator' that is designated by the gallery's user_id field. So to get the 5 latest galleries a user is in, I can do something like: included_in = @user.galleries.order('created_at DESC').uniq.first(5) # SELECT DISTINCT "galleries".* FROM "galleries" INNER JOIN "galleries_users" ON "galleries"."id" = "galleries_users"."gallery_id" WHERE "galleries_users"."user_id" = 10 ORDER BY created_at DESC LIMIT 5 and to get the 5 latest galleries they've created, I can do: created = Gallery.where(user_id: id).order('created_at DESC').uniq.first(5) # SELECT DISTINCT "galleries".* FROM "galleries" WHERE "galleries"."user_id" = 10 ORDER BY created_at DESC LIMIT 5 I want to display these two together, so that it's the 5 latest galleries that they've created OR they're in. Something like the equivalent of: (included_in + created).order('created_at DESC').uniq.first(5) Does anyone know how to construct an efficient query or post-query loop that does this?

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• looping and arrays

  - by user1838418

  Hi I'm trying to construct a loop to execute 16 states of the 8 4 2 1 code in (C++) while( condition) { double Bubble[16], Bubble1[16]; Bubble[0] = ( a-2 - (b-2) ) + ( c-2 - (d-2)); // represents 0000 Bubble[1] = ( a-2 - (b-2) ) + ( c-2 - (d+2)); // represents 0001 Bubble[2] = ( a-2 - (b-2) ) + ( c+2 - (d-2)); // represents 0010 Bubble[3] = ( a-2 - (b-2) ) + ( c+2 - (d+2)); //represents 0011 ....... Bubble[15] =(a+2 - (b+2) ) + ( c+2 - (d+2)); //represents 1111 } Is there an easy way of coding using for loops? instead of writing bubble[] every time? 0 stands for -2 and 1 stands for +2. So I have 4 variables and each one need to be incremented and/or decremented. Can this be done using for loop? Appreciate your help

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• Generating Fibonacci series in F#

  - by photo_tom

  I'm just starting to learn F# using VS2010 and below is my first attempt at generating the Fibonacci series. What I'm trying to do is to build a list of all numbers less than 400. let fabList = let l = [1;2;] let mutable a = 1 let mutable b = 2 while l.Tail < 400 do let c = a + b l.Add(c) let a = b let b = c My first problem is that on the last statement, I'm getting an error message "Incomplete structured construct at or before this point in expression" on the last line. I don't understand what I'm doing wrong here. While this seems to be an obvious way to build the list in a fairly efficient way (from a c++/C# programmer), from what little I know of f#, this doesn't seem to feel to be the right way to do the program. Am I correct in this feeling?

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• select row from table and substitute a field with one from another column if it exists

  - by EarthMind

  I'm trying construct a PostgreSQL query that does the following but so far my efforts have been in vain. Problem: There are two tables: A and B. I'd like to select all columns from table A (having columns: id, name, description) and substitute the "A.name" column with the value of the column "B.title" from table B (having columns: id, table_A_id title, langcode) where B.table_A_id is 5 and B.langcode is "nl" (if there are any rows). My attempts: SELECT A.name, case when exists(select title from B where table_A_id = 5 and langcode= 'nl') then B.title else A.name END FROM A, B WHERE A.id = 5 and B.table_A_id = 5 and B.langcode = 'nl' -- second try: SELECT COALESCE(B.title, A.name) as name from A, B where A.id = 5 and B.table_A_id = 5 and exists(select title from B where table_A_id = 5 and langcode= 'nl') I've tried using a CASE and COALESCE() but failed due to my inexperience with both concepts. Thanks in advance.

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• antlr: Best practice to integrate generated parser into the system

  - by green

  Here is the background, I am trying to create a DSL to allow customer write simple scripts to query into our mongodb based database. I choose antlr to implement the DSL. From my understanding (and pls let me know if it's not correct) there are 2 approaches to integrate antlr generated parser into the system: Embed code into the grammar file so that the generated parser could be used directly to make query to the database and return result in a certain format (e.g. json encoded) Keep the parser purely a parser, after feed the DSL file to it, and construct the query in another class by retrieving the AST from generated parser class So antlrers, which one do you think is the way I as an antlr newbie should go? Can you list the pros and cos of each approach, or you have other way to recommend?

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• Is Android IPC plumbing exposed in any official and/or supported way?

  - by mathrick

  I'm interested in knowing how much the IPC mechanisms are meant to be exposed to the outside world. That is, if I wanted to impersonate a dalvik VM instance without having my app actually written in Java, am I allowed to do so, or will the protocol change the next time I look away from the screen? If it's allowed, what are the stability guarantees or lack thereof? Is there anything like documentation, or am I supposed just to read the fine sources on android.git.kernel.org? The purpose of it all would be to write apps in !Java languages while retaining the ability to construct GUIs. I don't care or mind if the code is technically inside a dalvik process as a JNI callout, what I'm interested in is "if I'm really good at pretending I'm Java over the wire, can I do everything actual Java code can? Or is there something that's only available as Java bytecode and nothing else?"

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• include() Why should I not use it?

  - by aliov

  I am working through an older php mysql book written in 2003. The author uses the include() function to construct html pages by including header.inc, footer.inc, main.inc files, etc. Now I find out that this is not allowed in the default ini settings, (allow_url_include is set to Off) after I got many warnings from the server. I noticed also that you can use include without the parenthesis. I tried this and it works and I get no error messages or warnings. Are the two different? That is, is include() different from include ?

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