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  • How does a WCF server inform a WCF client about changes? (Better solution then simple polling, e.g.

    - by Ian Ringrose
    see also "WCF push to client through firewall" I need to have a WCF client that connect to a WCF server, then when some of the data changes on the server the clients need to update its display. As there is likely to be a firewall between the clients and the server. All communications must be over HTTP The server can not make an (physical) outgoing call to the client. As I am writing both the client and the server I do not need to limit the solution to only using soap etc. I am looking for built in surport for "long polling" / "Comet" etc Thanks for the most informative answer from Drew Marsh on how to implement long polling in WCF. However I thought the main “selling point” of WCF was that you could do this sort of thing just by configuring the channels to be used in the config file. E.g I want a channel that logically two way but physically incoming only.

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  • Using code in both Actionscript3 and Javascript

    - by Ian
    Here's an interesting architectural query. I have a piece of code that needs to run on the server (under Node.js) and on the client (in a Flash 10 app written with Actionscript 3). The code is mostly fairly intricate object manipulation, it doesn't make any API calls, and works fine in both contexts. So far the project is just a demo, so I've been happy to copy and paste the code into both places. But it might be quite interesting to move forward with this. So how would you do it? I assume there is no easy way to get the Flash SDK (has to build without an IDE) to read and do something useful with a .js file. My only thought is that I could write a code-generator that takes the .js file and places it in an ActionScript wrapper. Are there any obvious approaches that I've missed? Just to pre-empt an obvious answer, I know about cross-platform languages like HaXe.

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  • How to make Databinding type safe and support refactoring

    - by Ian Ringrose
    When I wish to bind a control to a property of my object, I have to provide the name of the property as a string. This is not very good because: If the property is removed or renamed, I don’t get a compiler warning. If a rename the property with a refactoring tool, it is likely the data binding will not be updated. I don’t get an error until runtime if the type of the property is wrong, e.g. binding an integer to a date chooser. Is there a design-paten that gets round this, but still has the ease of use of data-binding? (This is a problem in WinForm, Asp.net and WPF and most likely lots of other systems) I have now found "workarounds for nameof() operator in C#: typesafe databinding" that also has a good starting point for a solution.

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  • ADO/SQL Server: What is the error code for "timeout expired"?

    - by Ian Boyd
    i'm trying to trap a "timeout expired" error from ADO. When a timeout happens, ADO returns: Number: 0x80040E31 (DB_E_ABORTLIMITREACHED in oledberr.h) SQLState: HYT00 NativeError: 0 The NativeError of zero makes sense, since the timeout is not a function of the database engine (i.e. SQL Server), but of ADO's internal timeout mechanism. The Number (i.e. the COM hresult) looks useful, but the definition of DB_E_ABORTLIMITREACHED in oledberr.h says: Execution stopped because a resource limit was reached. No results were returned. This error could apply to things besides "timeout expired" (some potentially server-side), such as a governor that limits: CPU usage I/O reads/writes network bandwidth and stops a query. The final useful piece is SQLState, which is a database-independent error code system. Unfortunately the only reference for SQLState error codes i can find have no mention of HYT00. What to do? What do do? Note: i can't trust 0x80040E31 (DB_E_ABORTLIMITREACHED) to mean "timeout expired", anymore than i could trust 0x80004005 (E_UNSPECIFIED_ERROR) to mean "Transaction was deadlocked on lock resources with another process and has been chosen as the deadlock victim". My pseudo-question becomes: does anyone have documentation on what the SQLState "HYT000" means? And my real question still remains: How can i specifically trap an ADO timeout expired exception thrown by ADO? Gotta love the questions where the developer is trying to "do the right thing", but nobody knows how to do the right thing. Also gotta love how googling for DB_E_ABORTLIMITREACHED and this question is #9, with MSDN nowhere to be found. Update 3 From the OLEdb ICommand.Execute reference: DB_E_ABORTLIMITREACHED Execution has been aborted because a resource limit has been reached. For example, a query timed out. No results have been returned. "For example", meaning not an exhaustive list.

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  • IE8 CSS Table Effect

    - by Ian
    I've been trying to make this cross browser (specifically IE), but I do not want to use tables. I will not be able to specify the container width with CSS because its contents (the image) will dynamically change with Javascript, so I need the container to 'auto-size' horizontally. The desired effect would be a centered image with two sets of text (one of the left and one of the left) directly underneath the image, aligned to it's inner edges. Example (Doesn't work on IE): http://pastehtml.com/view/19pbyw9.html <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <style type="text/css"> #container { display:table; } </style> </head> <body> <center> <div id="container"> <img src="http://www.google.com/intl/en_ALL/images/srpr/logo1w.png" alt="" /><br /> <span style="float: left;">test</span> <span style="float: right; text-align: right;">test2</span> </div> </center> </body> </html>

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  • C#, WPF. Length of string that will fit in a specific width.

    - by Ian
    Hi, I'm sure I'm missing something obvious, I have an area in which I intend to draw text. I know its (the area) height and width. I wish to know how many characters/Words will fit in the width, characters preferably. Second question, If the line is too long I'll want to draw a second line, so I guess I need to get the height of the text as well, including what ever it considers the right vertical padding? I'd also rather like to know the inverse, i.e. how many characters I can fit in a specific width. I assume the fact that WPF isn't constrained to pixels will have some bearing on the answer? Ultimately I'm planning on wrapping text around irregular shaped images embedded in the text. Any pointers in the right direction would be great. Thanks

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  • Best way to model Installation logic/flow

    - by Ian
    Hi All, We are currently working on designing the installer for our product. We are currently on the design phase and I'm wondering what is the best diagram (UML or not) to use when modeling installation logic or flow? Currently, we are using the good'ol flowchart. Thanks!

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  • How to sed search and replace without changing ownership

    - by Ian
    I found this command line search and replace example: find . -type f -print0 | xargs -0 sed -i 's/find/replace/g' It worked fine except it changed the date and file ownership on EVERY file it searched through, even those that did not contain the search text. What's a better solution to this task? Thanks.

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  • XSLT: Is there a way to "inherit" canned functionality?

    - by Ian Boyd
    i am once again having to cobble together a bit of XSLT into order to turn generated XML into (rather than simply generating HTML). i'm having huge deja-vu this time again. i'm once again having to solve again basic problems, e.g.: how to convert characters into valid html entity references how to preserve whitespace/carriage returns when converting to html how to convert to HTML as opposed to xhtml how to convert dates from xml format into presentable format how to tear apart strings with substring This is all stuff that i've solved many times before. But every time i come back to XSLT i have to start from scratch, re-inventing the wheel every time. If it were a programming language i would have a library of canned functions and procedures i can call. i would have subroutines to perform the commonly repeated tasks. i would inherit from a base class that already implements the ugly boilerplate stuff. Is there any way in XSLT to grow, expand and improve the ecosystem with canned code?

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  • How to I serialize a large graph of .NET object into a SQL Server BLOB without creating a large bu

    - by Ian Ringrose
    We have code like: ms = New IO.MemoryStream bin = New System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bin.Serialize(ms, largeGraphOfObjects) dataToSaveToDatabase = ms.ToArray() // put dataToSaveToDatabase in a Sql server BLOB But the memory steam allocates a large buffer from the large memory heap that is giving us problems. So how can we stream the data without needing enough free memory to hold the serialized objects. I am looking for a way to get a Stream from SQL server that can then be passed to bin.Serialize() so avoiding keeping all the data in my processes memory. Likewise for reading the data back... Some more background. This is part of a complex numerical processing system that processes data in near real time looking for equipment problems etc, the serialization is done to allow a restart when there is a problem with data quality from a data feed etc. (We store the data feeds and can rerun them after the operator has edited out bad values.) Therefore we serialize the object a lot more often then we de-serialize them. The objects we are serializing include very large arrays mostly of doubles as well as a lot of small “more normal” objects. We are pushing the memory limit on a 32 bit system and make the garage collector work very hard. (Effects are being made elsewhere in the system to improve this, e.g. reusing large arrays rather then create new arrays.) Often the serialization of the state is the last straw that courses an out of memory exception; our peak memory usage is while this serialization is being done. I think we get large memory pool fragmentation when we de-serialize the object, I expect there are also other problem with large memory pool fragmentation given the size of the arrays. (This has not yet been investigated, as the person that first looked at this is a numerical processing expert, not a memory management expert.) Are customers use a mix of Sql Server 2000, 2005 and 2008 and we would rather not have different code paths for each version of Sql Server if possible. We can have many active models at a time (in different process, across many machines), each model can have many saved states. Hence the saved state is stored in a database blob rather then a file. As the spread of saving the state is important, I would rather not serialize the object to a file, and then put the file in a BLOB one block at a time. Other related questions I have asked How to Stream data from/to SQL Server BLOB fields? Is there a SqlFileStream like class that works with Sql Server 2005?

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  • SQL Server: Clustering by timestamp; pros/cons

    - by Ian Boyd
    I have a table in SQL Server, where i want inserts to be added to the end of the table (as opposed to a clustering key that would cause them to be inserted in the middle). This means I want the table clustered by some column that will constantly increase. This could be achieved by clustering on a datetime column: CREATE TABLE Things ( ... CreatedDate datetime DEFAULT getdate(), [timestamp] timestamp, CONSTRAINT [IX_Things] UNIQUE CLUSTERED (CreatedDate) ) But I can't guaranteed that two Things won't have the same time. So my requirements can't really be achieved by a datetime column. I could add a dummy identity int column, and cluster on that: CREATE TABLE Things ( ... RowID int IDENTITY(1,1), [timestamp] timestamp, CONSTRAINT [IX_Things] UNIQUE CLUSTERED (RowID) ) But you'll notice that my table already constains a timestamp column; a column which is guaranteed to be a monotonically increasing. This is exactly the characteristic I want for a candidate cluster key. So I cluster the table on the rowversion (aka timestamp) column: CREATE TABLE Things ( ... [timestamp] timestamp, CONSTRAINT [IX_Things] UNIQUE CLUSTERED (timestamp) ) Rather than adding a dummy identity int column (RowID) to ensure an order, I use what I already have. What I'm looking for are thoughts of why this is a bad idea; and what other ideas are better. Note: Community wiki, since the answers are subjective.

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  • My app crashes after multiple rotates

    - by Ian Rae
    My app is crashing when I try and rotate it more than a couple of times. I first thought it was just the iPhone Simulator, so I loaded the app onto an iPod touch, and it crashed after fewer rotates in a row. I suspect it's a memory leak in one of my rotate methods. The only place I can think that the crash is being caused is in willRotateToInterfaceOrientation:duration:. The only two methods related to rotate that I've added/extended are shouldAutorotateToInterfaceOrientation: and willRotateToInterfaceOrientation:duration and I don't think it's the first because it only contains the two words: return YES;. Here is my willRotateToInterfaceOrientation:duration: method so you can review it and see where the possible memory leak is. -(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)orientation duration:(NSTimeInterval)duration { UIFont *theFont; if ((orientation == UIInterfaceOrientationLandscapeLeft) || (orientation == UIInterfaceOrientationLandscapeRight)) { theFont = [yearByYear.font fontWithSize:16.0]; yearByYear.font = theFont; [theview setContentSize:CGSizeMake(460.0f, 635.0f)]; } else { theFont = [yearByYear.font fontWithSize:10.0]; yearByYear.font = theFont; [theview setContentSize:CGSizeMake(300.0f, 460.0f)]; } [theFont release]; } yearByYear is a UITextView theview is a UIScrollView if anyone has any idea of why my app is crashing, I would be greatly appreciative.

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  • Any open source back test engine using bloomberg tick-by-tick data?

    - by Ian Xu
    I have a back test on index futures to do. I've finished the test on 1-minute OHLC data and the result is OK. Further I want to opt our tick-by-tick data downloaded from Bloomberg. I have browsed the internet and found that several trading platforms are available for such function but Bloomberg is not in the data source providers list. So I think these are not suitable for my case. I'm wondering whether there is any open-source engine that I may embed to finish the test?

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  • Redis - Records Fall Off

    - by Ian
    With memcache, when you exceed the available ram, it automatically drops the oldest records off the end of the stack.. Is there a way to do this with redis? I'm trying to find ways to avoid running in to a write error (when there's no more available ram), other than setting a timeout. The only reason the timeout isn't useful, it because it doesn't guaranty the ability to write.

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  • Delphi: Alternative to using Reset/ReadLn for text file reading

    - by Ian Boyd
    i want to process a text file line by line. In the olden days i loaded the file into a StringList: slFile := TStringList.Create(); slFile.LoadFromFile(filename); for i := 0 to slFile.Count-1 do begin oneLine := slFile.Strings[i]; //process the line end; Problem with that is once the file gets to be a few hundred megabytes, i have to allocate a huge chunk of memory; when really i only need enough memory to hold one line at a time. (Plus, you can't really indicate progress when you the system is locked up loading the file in step 1). The i tried using the native, and recommended, file I/O routines provided by Delphi: var f: TextFile; begin Reset(f, filename); while ReadLn(f, oneLine) do begin //process the line end; Problem withAssign is that there is no option to read the file without locking (i.e. fmShareDenyNone). The former stringlist example doesn't support no-lock either, unless you change it to LoadFromStream: slFile := TStringList.Create; stream := TFileStream.Create(filename, fmOpenRead or fmShareDenyNone); slFile.LoadFromStream(stream); stream.Free; for i := 0 to slFile.Count-1 do begin oneLine := slFile.Strings[i]; //process the line end; So now even though i've gained no locks being held, i'm back to loading the entire file into memory. Is there some alternative to Assign/ReadLn, where i can read a file line-by-line, without taking a sharing lock? i'd rather not get directly into Win32 CreateFile/ReadFile, and having to deal with allocating buffers and detecting CR, LF, CRLF's. i thought about memory mapped files, but there's the difficulty if the entire file doesn't fit (map) into virtual memory, and having to maps views (pieces) of the file at a time. Starts to get ugly. i just want Reset with fmShareDenyNone!

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  • Why is OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, true, true) causing an OCR running error?

    - by Ian Wells
    Hi folks, I am using MODI to read tiff images and do what I need to do with the text. Some images work fine and then other tiff images always cause the method, OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, true, true) to fail. I have researched this and tried different variations such as 'false','false' in the parameter list. I have also tried SYSDEFAULT instead of English but I still get the error. Can anyone please tell me why it would fail on some tiff images and not on others? I have done some research and found this answer: One possible cause is MODI trying to process a file without any recognisable text. A blank document, or one which has only drawings/scribbles and is effectively blank, will cause this exception. Obviously this is not good enough as there is no way I can have an app that decides to OCR some images and not others. I handle the exception, but the OCR object is not then initalised so I can't do what I need to do from there. This is a bloody nightmare! Why can't the method just do it's bloody job and if the image has some unreadable pages then just ignore them? I am using Windows 7 Ultimate and Office 2007 Ultimate. Visual Studio version is 2008 Thanks, IW

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  • Delphi 5: Ideas for simulating "Obsolete" or "Deprecated" methods?

    - by Ian Boyd
    i want to mark a method as obsolete, but Delphi 5 doesn't have such a feature. For the sake of an example, here is a made-up method with it's deprecated and new preferred form: procedure TStormPeaksQuest.BlowHodirsHorn; overload; //obsolete procedure TStormPeaksQuest.BlowHodirsHorn(UseProtection: Boolean); overload; Note: For this hypothetical example, we assume that using the parameterless version is just plain bad. There are problems with not "using protection" - which have no good solution. Nobody likes having to use protection, but nobody wants to not use protection. So we make the caller decide if they want to use protection or not when blowing Hodir's horn. If we default the parameterless version to continue not using protection: procedure TStormPeaksQuest.BlowHodirsHorn; begin BlowHodirsHorn(False); //No protection. Bad! end; then the developer is at risk of all kinds of nasty stuff. If we force the parameterless version to use protection: procedure TStormPeaksQuest.BlowHodirsHorn; begin BlowHodirsHorn(True); //Use protection; crash if there isn't any end; then there's a potential for problems if the developer didn't get any protection, or doesn't own any. Now i could rename the obsolete method: procedure TStormPeaksQuest.BlowHodirsHorn_Deprecatedd; overload; //obsolete procedure TStormPeaksQuest.BlowHodirsHorn(UseProtection: Boolean); overload; But that will cause a compile error, and people will bitch at me (and i really don't want to hear their whining). i want them to get a nag, rather than an actual error. i thought about adding an assertion: procedure TStormPeaksQuest.BlowHodirsHorn; //obsolete begin Assert(false, 'TStormPeaksQuest.BlowHodirsHorn is deprecated. Use BlowHodirsHorn(Boolean)'); ... end; But i cannot guarantee that the developer won't ship a version without assertions, causing a nasty crash for the customer. i thought about using only throwing an assertion if the developer is debugging: procedure TStormPeaksQuest.BlowHodirsHorn; //obsolete begin if DebugHook > 0 then Assert(false, 'TStormPeaksQuest.BlowHodirsHorn is deprecated. Use BlowHodirsHorn(Boolean)'); ... end; But i really don't want to be causing a crash at all. i thought of showing a MessageDlg if they're in the debugger (which is a technique i've done in the past): procedure TStormPeaksQuest.BlowHodirsHorn; //obsolete begin if DebugHook > 0 then MessageDlg('TStormPeaksQuest.BlowHodirsHorn is deprecated. Use BlowHodirsHorn(Boolean)', mtWarning, [mbOk], 0); ... end; but that is still too disruptive. And it has caused problems where the code is stuck at showing a modal dialog, but the dialog box wasn't obviously visible. i was hoping for some sort of warning message that will sit there nagging them - until they gouge their eyes out and finally change their code. i thought perhaps if i added an unused variable: procedure TStormPeaksQuest.BlowHodirsHorn; //obsolete var ThisMethodIsObsolete: Boolean; begin ... end; i was hoping this would cause a hint only if someone referenced the code. But Delphi shows a hint even if you don't call actually use the obsolete method. Can anyone think of anything else?

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  • SQL Server: Clutering by timestamp; pros/cons

    - by Ian Boyd
    i have a table in SQL Server, where i want inserts to be added to the end of the table (as opposed to a clustering key that would cause them to be inserted in the middle). This means i want the table clustered by some column that will constantly increase. This could be achieved by clustering on a datetime column: CREATE TABLE Things ( ... CreatedDate datetime DEFAULT getdate(), [timestamp] timestamp, CONSTRAINT [IX_Things] UNIQUE CLUSTERED (CreatedDate) ) But i can't guaranteed that two Things won't have the same time. So my requirements can't really be achieved by a datetime column. i could add a dummy identity int column, and cluster on that: CREATE TABLE Things ( ... RowID int IDENTITY(1,1), [timestamp] timestamp, CONSTRAINT [IX_Things] UNIQUE CLUSTERED (RowID) ) But you'll notice that my table already constains a timestamp column; a column which is guaranteed to be a monotonically increasing. This is exactly the characteristic i want for a candidate cluster key. So i cluster the table on the rowversion (aka timestamp) column: CREATE TABLE Things ( ... [timestamp] timestamp, CONSTRAINT [IX_Things] UNIQUE CLUSTERED (timestamp) ) Rather than adding a dummy identity int column (RowID) to ensure an order, i use what i already have. What i'm looking for are thoughts of why this is a bad idea; and what other ideas are better. Note: Community wiki, since the answers are subjective.

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  • Handling XMLHttpRequest to call external application

    - by Ian
    I need a simple way to use XMLHttpRequest as a way for a web client to access applications in an embedded device. I'm getting confused trying to figure out how to make something thin and light that handles the XMLHttpRequests coming to the web server and can translate those to application calls. The situation: The web client using Ajax (ExtJS specifically) needs to send and receive asynchronously to an existing embedded application. This isn't just to have a thick client/thin server, the client needs to run background checking on the application status. The application can expose a socket interface, with a known set of commands, events, and configuration values. Configuration could probably be transmitted as XML since it comes from a SQLite database. In between the client and app is a lighttpd web server running something that somehow handles the translation. This something is the problem. What I think I want: Lighttpd can use FastCGI to route all XMLHttpRequest to an external process. This process will understand HTML/XML, and translate between that and the application's language. It will have custom logic to simulate pushing notifications to the client (receive XMLHttpRequest, don't respond until the next notification is available). C/C++. I'd really like to avoid installing Java/PHP/Perl on an embedded device. So I'll need more low level understanding. How do I do this? Are there good C++ libraries for interpreting the CGI headers and HTML so that I don't have to do any syntax processing, I can just deal with the request/response contents? Are there any good references to exactly what goes on, server side, when handling the XMLHttpRequest and CGI interfaces? Is there any package that does most of this job already, or will I have to build the non-HTTP/CGI stuff from scratch? Thanks for any help! I am really having trouble learning about the server side of these technologies.

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  • G++, compiler warnings, c++ templates

    - by Ian
    During the compilatiion of the C++ program those warnings appeared: c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bc:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bits/stl_algo.h:2317: instantiated from `void std::partial_sort(_RandomAccessIterator, _RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Object<double>**, std::vector<Object<double>*, std::allocator<Object<double>*> > >, _Compare = sortObjects<double>]' c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bits/stl_algo.h:2506: instantiated from `void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Object<double>**, std::vector<Object<double>*, std::allocator<Object<double>*> > >, _Size = int, _Compare = sortObjects<double>]' c:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/c++/3.4.5/bits/stl_algo.h:2589: instantiated from `void std::sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<Object<double>**, std::vector<Object<double>*, std::allocator<Object<double>*> > >, _Compare = sortObjects<double>]' io/../structures/objects/../../algorithm/analysis/../../structures/list/ObjectsList.hpp:141: instantiated from `void ObjectsList <T>::sortObjects(unsigned int, T, T, T, T, unsigned int) [with T = double]' I do not why, because all objects have only template parameter T, their local variables are also T. The only place, where I am using double is main. There are objects of type double creating and adding into the ObjectsList... Object <double> o1; ObjectsList <double> olist; olist.push_back(o1); .... T xmin = ..., ymin = ..., xmax = ..., ymax = ...; unsigned int n = ...; olist.sortAllObjects(xmin, ymin, xmax, ymax, n); and comparator template <class T> class sortObjects { private: unsigned int n; T xmin, ymin, xmax, ymax; public: sortObjects ( const T xmin_, const T ymin_, const T xmax_, const T ymax_, const int n_ ) : xmin ( xmin_ ), ymin ( ymin_ ), xmax ( xmax_ ), ymax ( ymax_ ), n ( n_ ) {} bool operator() ( const Object <T> *o1, const Object <T> *o2 ) const { T dmax = (std::max) ( xmax - xmin, ymax - ymin ); T x_max = ( xmax - xmin ) / dmax; T y_max = ( ymax - ymin ) / dmax; ... return ....; } representing ObjectsList method: template <class T> void ObjectsList <T> ::sortAllObjects ( const T xmin, const T ymin, const T xmax, const T ymax, const unsigned int n ) { std::sort ( objects.begin(), objects.end(), sortObjects <T> ( xmin, ymin, xmax, ymax, n ) ); }

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