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  • Can't delete record via the datacontext it was retrieved from

    - by Antilogic
    I just upgraded one of my application's methods to use compiled queries (not sure if this is relevant). Now I'm getting contradicting error messages when I run the code. This is my method: MyClass existing = Queries.MyStaticCompiledQuery(MyRequestScopedDataContext, param1, param2).SingleOrDefault(); if (existing != null) { MyRequestScopedDataContext.MyClasses.DeleteOnSubmit(existing); } When I run it I get this message: Cannot remove an entity that has not been attached. Note that the compiled query and the DeleteOnSubmit reference the same DataContext. Still I figured I'd humor the application and add an attach command before the DeleteOnSubmit, like so: MyClass existing = Queries.MyStaticCompiledQuery(MyRequestScopedDataContext, param1, param2).SingleOrDefault(); if (existing != null) { MyRequestScopedDataContext.MyClasses.Attach(existing); MyRequestScopedDataContext.MyClasses.DeleteOnSubmit(existing); } BUT... When I run this code, I get a completely different contradictory error message: An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported. I'm at a complete loss... Does anyone else have some insight as to why I can't delete a record via the same DataContext I retrieved it from?

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  • Need help with an xpath query!

    - by gerrod
    Can anyone help with the following XPath question? Given the node-set: <table> <rows> <row> <value column="Product">Coal</value> <value column="Quantity">10000</value> </row> <row> <value column="Product">Iron</value> <value column="Quantity">5000</value> </row> <row> <value column="Product">Ore</value> <value column="Quantity">4000</value> </row> </rows> </table> I want to query to find the node sub-set with a given product name. Note that the product name is being supplied by an attribute of the current node being processed (i.e. "@name"). So when the @name attribute has the value of "Coal" I would expect this to be returned: <row> <value column="Product">Coal</value> <value column="Quantity">10000</value> </row> This is what I've come up with; I know it's wrong, because I don't get anything back. $table/rows/row[value[@column='Product'][text()=@name]] </code>

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  • When is a bool not a bool (compiler warning C4800)

    - by omatai
    Consider this being compiled in MS Visual Studio 2005 (and probably others): CPoint point1( 1, 2 ); CPoint point2( 3, 4 ); const bool point1And2Identical( point1 == point2 ); // C4800 warning const bool point1And2TheSame( ( point1 == point2 ) == TRUE ); // no warning What the...? Is the MSVC compiler brain-dead? As far as I can tell, TRUE is #defined as 1, without any type information. So by what magic is there any difference between these two lines? Surely the type of the expression inside the brackets is the same in both cases? [This part of the question now satisfactorily answered in the comments just below] Personally, I think that avoiding the warning by using the == TRUE option is ugly (though less ugly than the != 0 alternative, despite being more strictly correct), and it is better to use #pragma warning( disable:4800 ) to imply "my code is good, the compiler is an ass". Agree? Note - I have seen all manner of discussion on C4800 talking about assigning ints to bools, or casting a burger combo with large fries (hold the onions) to a bool, and wondering why there are strange results. I can't find a clear answer on what seems like a much simpler question... that might just shine line on C4800 in general.

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  • MediaWiki: how to hide users from the user list?

    - by Dave Everitt
    I've set up Mediawiki 1.15.1 for a client who has added two users by mistake. They now want to hide these users from the user list. It seems this is done via the $wgGroupPermissions array with $wgGroupPermissions['suppress']['hideuser'] = true;, but it isn't at all clear what entry this needs for the hiding to work, or whether a new group ('hidden' or whatever) has to be created first with $wgAddGroups['bureaucrat'] = true;. For now, I've added the two users to be hidden to the 'Oversight' group which explains 'Block a username, hiding it from the public (hideuser)', but they still appear on the Special:ListUsers page. At a loss as to how the MediWiki arrays alter options displayed in the interface, so far I've added this to LocalSettings.php: $wgGroupPermissions['suppress']['hideuser'] = true; $wgAddGroups['supress'] = true; Or - since they haven't actually added anything to the wiki - could they simply be removed from the MySQL users table - although MediaWiki warns against this? Has anyone else done this successfully? Update - this is a hole in MediaWiki admin (although there are workarounds). See this thread on MediaWIki Users and the note to the reply below.

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  • Linear Interpolation. How to implement this algorithm in C ? (Python version is given)

    - by psihodelia
    There exists one very good linear interpolation method. It performs linear interpolation requiring at most one multiply per output sample. I found its description in a third edition of Understanding DSP by Lyons. This method involves a special hold buffer. Given a number of samples to be inserted between any two input samples, it produces output points using linear interpolation. Here, I have rewritten this algorithm using Python: temp1, temp2 = 0, 0 iL = 1.0 / L for i in x: hold = [i-temp1] * L temp1 = i for j in hold: temp2 += j y.append(temp2 *iL) where x contains input samples, L is a number of points to be inserted, y will contain output samples. My question is how to implement such algorithm in ANSI C in a most effective way, e.g. is it possible to avoid the second loop? NOTE: presented Python code is just to understand how this algorithm works. UPDATE: here is an example how it works in Python: x=[] y=[] hold=[] num_points=20 points_inbetween = 2 temp1,temp2=0,0 for i in range(num_points): x.append( sin(i*2.0*pi * 0.1) ) L = points_inbetween iL = 1.0/L for i in x: hold = [i-temp1] * L temp1 = i for j in hold: temp2 += j y.append(temp2 * iL) Let's say x=[.... 10, 20, 30 ....]. Then, if L=1, it will produce [... 10, 15, 20, 25, 30 ...]

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  • Why is textbox.focus throwing the lostfocus event?

    - by cost
    I've seen a few similar questions on SO but nothing that seems to actually address the issue. Here's a simplified version of the function. Private Sub Check_Quantity(sender As System.Object, e As System.Windows.RoutedEventArgs) _ Handles textbox_quantity.LostFocus Dim worked As Boolean = Integer.TryParse(textbox_quantity.Text, quantity) If Not worked Then MsgBox("Enter a valid number for the quantity") textbox_quantity.Focus() textbox_quantity.SelectAll() quantity = 0 End If End Sub It's important to note that this is WPF. What I want to do is very simple. When someone finishes with the textbox the program checks that what they entered is a number. If it does it sticks this in an integer. If not, it tells them to fix it and keeps the focus on the textbox. The issue is a few things, but what it comes down to is this function runs in an infinite loop. This same function works fine in WinForms, but not in WPF. On some other questions people have said that the messagebox appearing causes focus to be lost, but in testing this isn't true. It still loops regardless of if the messagebox is called or not. The problem is the call to textbox_quantity.Focus(). Without that it works fine. Regardless of whether it's there or not though, focus is not set to the textbox, though textbox_quantity.Focus() still returns a value of true. Any thought of what's going on and maybe how I could fix it?

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  • FileNotFoundExcecption while inserting image into SDCard.

    - by Are
    Hi, I want to insert images into my SDCard.So I used below code m_cImagePath = "/sdcard/"+ String.format("%d.jpg", System.currentTimeMillis()); FileOutputStream lObjOutStream = null; try { lObjOutStream = new FileOutputStream(m_cImagePath); if (null != lObjOutStream && null != finalBitmap) { finalBitmap.compress(Bitmap.CompressFormat.JPEG, 85, lObjOutStream); lObjOutStream.close(); }catch(FileNotFoundException fe){ fe.printStackTrace(); } Sometimes it is giving FileNotFoundException even my SDCard had memory.When I remove some images from sdcard again it is working smoothly.Why this Happend?How can i know that file is inserted successfully in SDCard and Is there any functionality in Java1.5 to know available space of the SDCard like java 1.6?How can i know file length which is not before inserting into the SDCard(I searched in google and found that "when the file is not physically there then file.length() always gives 0" ).But before inserting i want to know the length of the file.Then Comparing this space to available SDCard space is simple. Note :I had an idea to use Unix command df sdcard using in Runtime class to found SDCard space. Please give me an idea in this problem. Regards, Android Developer

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  • JavaCC: How can I specify which token(s) are expected in certain context?

    - by java.is.for.desktop
    Hello, everyone! I need to make JavaCC aware of a context (current parent token), and depending on that context, expect different token(s) to occur. Consider the following pseudo-code: TOKEN <abc> { "abc*" } // recognizes "abc", "abcd", "abcde", ... TOKEN <abcd> { "abcd*" } // recognizes "abcd", "abcde", "abcdef", ... TOKEN <element1> { "element1" "[" expectOnly(<abc>) "]" } TOKEN <element2> { "element2" "[" expectOnly(<abcd>) "]" } ... So when the generated parser is "inside" a token named "element1" and it encounter "abcdef" it recognizes it as <abc>, but when its "inside" a token named "element2" it recognizes the same string as <abcd>. element1 [ abcdef ] // aha! it can only be <abc> element2 [ abcdef ] // aha! it can only be <abcd> If I'm not wrong, it would behave similar to more complex DTD definitions of an XML file. So, how can one specify, in which "context" which token(s) are valid/expected? NOTE: It would be not enough for my real case to define a kind of "hierarchy" of tokens, so that "abcdef" is always first matched against <abcd> and than <abc>. I really need context-aware tokens.

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  • crash when using stl vector at instead of operator[]

    - by Jamie Cook
    I have a method as follows (from a class than implements TBB task interface - not currently multithreading though) My problem is that two ways of accessing a vector are causing quite different behaviour - one works and the other causes the entire program to bomb out quite spectacularly (this is a plugin and normally a crash will be caught by the host - but this one takes out the host program as well! As I said quite spectacular) void PtBranchAndBoundIterationOriginRunner::runOrigin(int origin, int time) const // NOTE: const method { BOOST_FOREACH(int accessMode, m_props->GetAccessModes()) { // get a const reference to appropriate vector from member variable // map<int, vector<double>> m_rowTotalsByAccessMode; const vector<double>& rowTotalsForAccessMode = m_rowTotalsByAccessMode.find(accessMode)->second; if (origin != 129) continue; // Additional debug constrain: I know that the vector only has one non-zero element at index 129 m_job->Write("size: " + ToString(rowTotalsForAccessMode.size())); try { // check for early return... i.e. nothing to do for this origin if (!rowTotalsForAccessMode[origin]) continue; // <- this works if (!rowTotalsForAccessMode.at(origin)) continue; // <- this crashes } catch (...) { m_job->Write("Caught an exception"); // but its not an exception } // do some other stuff } } I hate not putting in well defined questions but at the moment my best phrasing is : "WTF?" I'm compiling this with Intel C++ 11.0.074 [IA-32] using Microsoft (R) Visual Studio Version 9.0.21022.8 and my implementation of vector has const_reference operator[](size_type _Pos) const { // subscript nonmutable sequence #if _HAS_ITERATOR_DEBUGGING if (size() <= _Pos) { _DEBUG_ERROR("vector subscript out of range"); _SCL_SECURE_OUT_OF_RANGE; } #endif /* _HAS_ITERATOR_DEBUGGING */ _SCL_SECURE_VALIDATE_RANGE(_Pos < size()); return (*(_Myfirst + _Pos)); } (Iterator debugging is off - I'm pretty sure) and const_reference at(size_type _Pos) const { // subscript nonmutable sequence with checking if (size() <= _Pos) _Xran(); return (*(begin() + _Pos)); } So the only difference I can see is that at calls begin instead of simply using _Myfirst - but how could that possibly be causing such a huge difference in behaviour?

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  • Is it possible to load an entire SQL Server CE database into RAM?

    - by DanM
    I'm using LinqToSql to query a small SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table via a foreign key, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of the appeal of LinqToSql. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view.

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  • Is it safe to use a boolean flag to stop a thread from running in C#

    - by Lirik
    My main concern is with the boolean flag... is it safe to use it without any synchronization? I've read in several places that it's atomic. class MyTask { private ManualResetEvent startSignal; private CountDownLatch latch; private bool running; MyTask(CountDownLatch latch) { running = false; this.latch = latch; startSignal = new ManualResetEvent(false); } // A method which runs in a thread public void Run() { startSignal.WaitOne(); while(running) { startSignal.WaitOne(); //... some code } latch.Signal(); } public void Stop() { running = false; startSignal.Set(); } public void Start() { running = true; startSignal.Set(); } public void Pause() { startSignal.Reset(); } public void Resume() { startSignal.Set(); } } Is this a safe way to design a task? Any suggestions, improvements, comments? Note: I wrote my custom CountDownLatch class in case you're wondering where I'm getting it from.

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  • Which CSS identifier is used for the selected tab in tabbed tables in browsers other than IE?

    - by David Navarre
    When you have a table on a form in Notes, you can choose to display only one row at a time (via the Special Table Row Display parameter on the Table Rows tab of the Table properties). In a Notes document displayed using Internet Explorer that contains such a table, a row is displayed with a cell for each "tab". The TD that serves as the tab for the selected "Notes table row" is assigned <td class="dominoSelTopTab">, while the other tabs get <td class="dominoTopTab">. However, when using other browsers, it's not nearly as simple. In Firefox, each "tab" ends up as a single-celled-single-row-table within the table with very little to identify it. <td><table border="1" cellpadding="2"> <tr><td><div align="center"><b>Tab 2</b></div></td></tr> </table></td> A non-selected tab would show as follows: <td><table border="1" cellpadding="2"> <tr><td><div align="center"><a name="1." href="/Projects/MyCSS.nsf/0c3b9489476440c085257a62006d97d6/d482a1767a4af77f85257a62006db064?OpenDocument&amp;TableRow=1.0#1." target="_self">Tab 1</a></div></td></tr> </table></td> So, the question is, how do I identify the selected tabs and the non-selected tabs when not using IE? Note: For those who are not Notes developers, the HTML is auto-generated from the visual design as laid out in the Notes designer client. I would replace it all with manual HTML, except there is so much of it that doing so would consume far too much time.

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  • What is the best way to wait for a GPS location fix?

    - by qtips
    Hi, Using my Android application, when a user does a certain action, a background service is started that fetches the current GPS location and saves it in a database in addition of doing some other stuff. In that service, I use the requestLocationUpdates() from the LocationManager class and wait until the onLocationChanged() of my LocationListener (which is implemented by the service) is fired. But what is the best way to wait for the onLocationChanged to fire? Should I simply poll on a variable and wait until it is set? Any tips? Note: I cannot simply write to the database in the onLocationChanged() because of some other stuff. EDIT: To clearfy my situation, I can present an example similar to my case: Let's say user pushes a button and a method myMethod is fired which will return some object. Then, in this myMethod I will register for location updates from the GPS (using requestLocationChanged) and in addition wait for the users location and use it for something. In other words, myMethod cannot return before the location is present. I don't know how I can use onLocationChanged in this case.

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  • Expose webservice directly to webclients or keep a thin server-side script layer in between?

    - by max
    Hi, I'm developing a REST webservice (Java, Jersey). The people I'm doing this for want to directly access the webservice via Javascript. Some instinct tells me this is not a good idea, but I cannot really explain that instinct. My natural approach would have been to have the webservice do the real logic and database access, but also have some (relatively thin) server-side script layer (e.g. in PHP). Clients would talk to the PHP layer which in turn would talk to the webservice. (The webservice would be pretty local to the apache/PHP server and implicitly trust calls from the script layer. The script layer would take care of session management.) (Btw, I am not talking about just hiding the webservice behind an Apache which simply redirects calls.) But as I find myself at a lack of words/arguments to explain my instinct, I wonder whether my instinct is right - note that while I have been developing all kinds of software in all kinds of languages and frameworks for like 17 years, this is the first time I develop a webservice. So my question is basically: what are your opinions? Are there any standard setups? Is my instinct totally wrong? Or partially? ;P Many thanks, Max PS: I might add a few bits of information about the planned usage of the whole application: will be accessed by different kinds of users, partly general public, partly privileged thus, all major OS/browser combinations can be expected as clients however, writing the client is not my responsibility will potentially have very high load/traffic logic of webservice will later be massively expanded for another product which is basically a superset of the functionality of the current project there is a significant likelihood that at some point an API should be exposed which can be used by 3rd party developers - obviously, with some restrictions at some point, the public view of the product should become accessible via smartphones, too (in other words, maybe a customized version of the site to adapt to the smaller display and different input methods)

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  • What should a teen dev do for practical experience in development?

    - by aviraldg
    What should a teen dev do for practical experience? If you want more details , then read on: I learnt programming when I was 9 , with GWBASIC (which I now hate) , which was what was taught @ school. That was done in a month. After that I learnt C++ and relearnt it (as I didn't know of templates and the STL before that) Recently I learnt PHP , SQL and Python. This was around the time I switched over to Ubuntu. I'd always loved the "GNUish" style of software development so I jumped right in. However , most of the projects that I found required extensive knowledge of their existing codebase. So , right now I'm this guy who knows a couple of languages and has written a couple of small programs ... but hasn't gone "big", if you get it. I would love suggestions of projects that are informal and small to medium sized , and do not require much knowledge of the codebase. Also note that I've looked at things like Google Summer of Code and sites like savannah.gnu.org and the first doesn't apply , since I'm still in school and the latter either has infeasable projects , or things that are too hard.

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  • problem in wordpress like delete rows in jquery

    - by Mac Taylor
    hey guys im trying to impelement a technique to delete stories with jquery animation exactly like wordpress this is my script part : $(function(){ $('#jqdelete').click(function() { $(this).parents('tr.box').animate( { backgroundColor: '#cb5555' }, 500).animate( { height: 0, paddingTop: 0, paddingBottom: 0 }, 500, function() { $(this).css( { 'display' : 'none' } ); }); }); }); and this is my html part <tr class='box'> <td> <a href=\"edit.php&pid=$pid\">$title</font></a></td> <td >$eki</td> <td> <a href='javascript:void(0)' id='jqdelete'> <img src=\"images/delete.gif\"></a> </td> </tr> but not working am i wrong in any part of my code ? Note : if i use div instead of tr and td , works fine , but i want to use this effect on my table rows thanx

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  • Accessing variables with different scope in C++

    - by Portablejim
    With #include <iostream> using namespace std; int a = 1; int main() { int a = 2; if(true) { int a = 3; cout << a << " " << ::a // Can I access a = 2 here? << " " << ::a << endl; } cout << a << " " << ::a << endl; } having the output 3 1 1 2 1 Is there a way to access the 'a' equal to 2 inside the if statement where there is the 'a' equal to 3, with the output 3 2 1 2 1 Note: I know this should not be done (and the code should not get to the point where I need to ask). This question is more "can it be done".

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  • C#: How to get all public (both get and set) string properties of a type

    - by Svish
    I am trying to make a method that will go through a list of generic objects and replace all their properties of type string which is either null or empty with a replacement. How is a good way to do this? I have this kind of... shell... so far: public static void ReplaceEmptyStrings<T>(List<T> list, string replacement) { var properties = typeof(T).GetProperties( -- What BindingFlags? -- ); foreach(var p in properties) { foreach(var item in list) { if(string.IsNullOrEmpty((string) p.GetValue(item, null))) p.SetValue(item, replacement, null); } } } So, how do I find all the properties of a type that are: Of type string Has public get Has public set ? I made this test class: class TestSubject { public string Public; private string Private; public string PublicPublic { get; set; } public string PublicPrivate { get; private set; } public string PrivatePublic { private get; set; } private string PrivatePrivate { get; set; } } The following does not work: var properties = typeof(TestSubject) .GetProperties(BindingFlags.Instance|BindingFlags.Public) .Where(ø => ø.CanRead && ø.CanWrite) .Where(ø => ø.PropertyType == typeof(string)); If I print out the Name of those properties I get there, I get: PublicPublic PublicPrivate PrivatePublic In other words, I get two properties too much. Note: This could probably be done in a better way... using nested foreach and reflection and all here... but if you have any great alternative ideas, please let me know cause I want to learn!

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  • Stop SQL returning the same result twice in a JOIN

    - by nbs189
    I have joined together several tables to get data i want but since I am new to SQL i can't figure out how to stop data being returned more than once. her's the SQL statement; SELECT T.url, T.ID, S.status, S.ID, E.action, E.ID, E.timestamp FROM tracks T, status S, events E WHERE S.ID AND T.ID = E.ID ORDER BY E.timestamp DESC The data that is returned is something like this; +----------------------------------------------------------------+ | URL | ID | Status | ID | action | ID | timestamp | +----------------------------------------------------------------+ | T.1 | 4 | hello | 4 | has uploaded a track | 4 | time | | T.2 | 3 | bye | 3 | has some news | 3 | time | | t.1 | 4 | more | 4 | has some news | 4 | time | +----------------------------------------------------------------+ That's a very basic example but does outline what happens. If you look at the third row the URL is repeated when there is a different status. This is what I want to happen; +-------------------------------------------------------+ | URL or Status | ID | action | timestamp | +-------------------------------------------------------+ | T.1 | 4 | has uploaded a track | time | | hello | 3 | has some news | time | | bye | 4 | has some news | time | +-------------------------------------------------------+ Please notice that the the url (in this case the mock one is T.1) is shown when the action is has uploaded a track. This is very important. The action in the events table is inserted on trigger of a status or track insert. If a new track is inserted the action is 'has uploaded a track' and you guess what it is for a status. The ID and timestamp is also inserted into the events table at this point. Note: There are more tables that go into the query, 3 more in fact, but I have left them out for simplicity.

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  • Creating simple calculator with bison & flex in C++ (not C)

    - by ak91
    Hey, I would like to create simple C++ calculator using bison and flex. Please note I'm new to the creating parsers. I already found few examples in bison/flex but they were all written in C. My goal is to create C++ code, where classes would contain nodes of values, operations, funcs - to create AST (evaluation would be done just after creating whole AST - starting from the root and going forward). For example: my_var = sqrt(9 ** 2 - 32) + 4 - 20 / 5 my_var * 3 Would be parsed as: = / \ my_var + / \ sqrt - | / \ - 4 / / \ / \ ** 32 20 5 / \ 9 2 and the second AST would look like: * / \ my_var 3 Then following pseudocode reflects AST: ast_root = create_node('=', new_variable("my_var"), exp) where exp is: exp = create_node(OPERATOR, val1, val2) but NOT like this: $$ = $1 OPERATOR $3 because this way I directly get value of operation instead of creation the Node. I believe the Node should contain type (of operation), val1 (Node), val2 (Node). In some cases val2 would be NULL, like above mentioned sqrt which takes in the end one argument. Right? It will be nice if you can propose me C++ skeleton (without evaluation) for above described problem (including *.y file creating AST) to help me understand the way of creating/holding Nodes in AST. Code can be snipped, just to let me get the idea. I'll also be grateful if you point me to an existing (possibly simple) example if you know any. Thank you all for your time and assistance!

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  • Why would one want to use the public constructors on Boolean and similar immutable classes?

    - by Robert J. Walker
    (For the purposes of this question, let us assume that one is intentionally not using auto(un)boxing, either because one is writing pre-Java 1.5 code, or because one feels that autounboxing makes it too easy to create NullPointerExceptions.) Take Boolean, for example. The documentation for the Boolean(boolean) constructor says: Note: It is rarely appropriate to use this constructor. Unless a new instance is required, the static factory valueOf(boolean) is generally a better choice. It is likely to yield significantly better space and time performance. My question is, why would you ever want to get a new instance in the first place? It seems like things would be simpler if constructors like that were private. For example, if they were, you could write this with no danger (even if myBoolean were null): if (myBoolean == Boolean.TRUE) It'd be safe because all true Booleans would be references to Boolean.TRUE and all false Booleans would be references to Boolean.FALSE. But because the constructors are public, someone may have used them, which means that you have to write this instead: if (Boolean.TRUE.equals(myBoolean)) But where it really gets bad is when you want to check two Booleans for equality. Something like this: if (myBooleanA == myBooleanB) ...becomes this: if ( (myBooleanA == null && myBooleanB == null) || (myBooleanA == null && myBooleanA.equals(myBooleanB)) ) I can't think of any reason to have separate instances of these objects which is more compelling than not having to do the nonsense above. What say you?

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  • How can I create a rules engine without using eval() or exec()?

    - by Angela
    I have a simple rules/conditions table in my database which is used to generate alerts for one of our systems. I want to create a rules engine or a domain specific language. A simple rule stored in this table would be..(omitting the relationships here) if temp > 40 send email Please note there would be many more such rules. A script runs once daily to evaluate these rules and perform the necessary actions. At the beginning, there was only one rule, so we had the script in place to only support that rule. However we now need to make it more scalable to support different conditions/rules. I have looked into rules engines , but I hope to achieve this in some simple pythonic way. At the moment, I have only come up with eval/exec and I know that is not the most recommended approach. So, what would be the best way to accomplish this?? ( The rules are stored as data in database so each object like "temperature", condition like "/=..etc" , value like "40,50..etc" and action like "email, sms, etc.." are stored in the database, i retrieve this to form the condition...if temp 50 send email, that was my idea to then use exec or eval on them to make it live code..but not sure if this is the right approach )

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  • Visual Studio internal project references not always working

    - by Chris
    I am using Visual Studio and a solution with 10 or so projects in (mostly VB, some C#) which have various dependencies set up. Usually when I compile the solution it works fine. Occasionally when I do it I get a build error saying that one of the projects referenced is the wrong version (I think always the same one, possibly may be two that can cause problems). In this case going to the solution explorer and right clicking on the mentioned project and saying "rebuild" followed by another full build makes it work fine. I assume there is something set up wrong somewhere but I didn't set up the solution myself initially and a quick look through doesn't show anything immediately wrong. It feels like there is some kind of race condition, that VS is internally setting the version number of the project it needs before that project has been rebuilt and thus gets it wrong or something like that but I'm sure VS should handle all this sort of thing properly. Can anybody please suggest places that I could check for whether this has been correctly set up... And I should finally note that since I don't have reliable repro of this I may not be able to respond to questions too quickly. For example the obvious one of "Could you give the exact error message" will have to wait since I didn't think to copy it this morning, it was only after I cleared it up with the above steps that I thought to post here. Similarly any solutions may take a while to confirm.

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  • SQL return ORDER BY result as an array

    - by EarthMind
    Is it possible to return groups as an associative array? I'd like to know if a pure SQL solution is possible. Note that I release that I could be making things more complex unnecessarily but this is mainly to give me an idea of the power of SQL. My problem: I have a list of words in the database that should be sorted alphabetically and grouped into separate groups according to the first letter of the word. For example: ape broom coconut banana apple should be returned as array( 'a' => 'ape', 'apple', 'b' => 'banana', 'broom', 'c' => 'coconut' ) so I can easily created sorted lists by first letter (i.e. clicking "A" only shows words starting with a, "B" with b, etc. This should make it easier for me to load everything in one query and make the sorted list JavaScript based, i.e. without having to reload the page (or use AJAX). Side notes: I'm using PostgreSQL but a solution for MySQL would be fine too so I can try to port it to PostgreSQL. Scripting language is PHP.

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  • Choropleth mapping issue in R

    - by chasec
    I am trying to follow the tutorial described here: http://www.thisisthegreenroom.com/2009/choropleths-in-r/ The below code executes, but it is either not matching my dataset with the maps_counties data properly, or it isn't plotting it in the order I would expect. For example, the resulting areas for the greater NYC area show no density while random counties in PA show the highest density. The general format of my data table is: county state count fairfield connecticut 17 hartford connecticut 6 litchfield connecticut 3 new haven connecticut 12 ... ... westchester new york 70 yates new york 1 luzerne pennsylvania 1 Note this data is in order by state and then county and includes data for CT, NJ, NY, & PA. First, I read in my data set: library(maps) library(RColorBrewer) d <- read.table("gissum.txt", sep="\t", header=TRUE) #Concatenate state and county info to match maps library d$stcon <- paste(d$state, d$county, sep=",") #Color bins colors = brewer.pal(5, "PuBu") d$colorBuckets <- as.factor(as.numeric(cut(d$count,c(0,10,20,30,40,50,300)))) Here is my matching mapnames <- map("county",plot=FALSE)[4]$names colorsmatched <- d$colorBuckets [na.omit(match(mapnames ,d$stcon))] Plotting: map("county" ,c("new york","new jersey", "connecticut", "pennsylvania") ,col = colors[d$colorBuckets[na.omit(match(mapnames ,d$stcon))]] ,fill = TRUE ,resolution = 0 ,lty = 0 ,lwd= 0.5 ) map("state" ,c("new york","new jersey", "connecticut", "pennsylvania") ,col = "black" ,fill=FALSE ,add=TRUE ,lty=1 ,lwd=2 ) map("county" ,c("new york","new jersey", "connecticut", "pennsylvania") ,col = "black" ,fill=FALSE ,add=TRUE , lty=1 , lwd=.5 ) title(main="Respondent Home ZIP Codes by County") I am sure I am missing something basic re: the order in which the maps function plots items - but I can't seem to figure it out. Thanks for the help. Please let me know if you need any more information.

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