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• Porting Windows C++ to Standard (Linux) C++ - WSAGetLastError()

  - by Donal Rafferty

  I am currently porting some Windows mobile C++ code to standard C++. So I am trying to find alternatives for windows specific functions. I have had very little luck in finding a standard C++ function that can help me replace the WSAGetLastError() windows specific function. WSAGetLastError() returns error numbers for errors that occur with sockets in windows. So I was wondering if anyone was aware of a way to replace this function in standard c++? A way to get different error numbers for different outcomes of connecting/dissconection a socket would be sufficent.

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• Partially parse C++ for a domain-specific language

  - by PierreBdR

  I would like to create a domain specific language as an augmented-C++ language. I will need mostly two types of contructs: Top-level constructs for specialized types or declarations In-code constructs, i.e. to add primitives to make functions calls or idiom easier The language will be used for scientific computing purposes, and will ultimately be translated into plain C++. C++ has been chosen as it seems to offer a good compromise between: ease of use, efficiency and availability of a wide range of libraries. A previous attempt using flex and bison failed due to the complexity of the C++ syntax. The existing parser can still fail on some constructs. So we want to start over, but on better bases. Do you know about similar projects? And if you attempted to do so, what tools would you use? What would be the main pitfalls? Would you have recommendations in term of syntax?

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• In SQL how do I get the maximum value for an integer?

  - by CoffeeMonster

  Hi, I am trying to find out the maximum value for an integer (signed or unsigned) from a MySQL database. Is there a way to pull back this information from the database itself? Are there any built-in constants or functions I can use (either standard SQL or MySQL specific). At http://dev.mysql.com/doc/refman/5.0/en/numeric-types.html it lists the values - but is there a way for the database to tell me. The following gives me the MAX_BIGINT - what I'd like is the MAX_INT. SELECT CAST( 99999999999999999999999 AS SIGNED ) as max_int; # max_int | 9223372036854775807 Thanks in advance,

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• How to check for C++ copy ellision

  - by Steve

  I ran across this article on copy ellision in C++ and I've seen comments about it in the boost library. This is appealing, as I prefer my functions to look like verylargereturntype DoSomething(...) rather than void DoSomething(..., verylargereturntype& retval) So, I have two questions about this Google has virtually no documentation on this at all, how real is this? How can I check that this optimization is actually occuring? I assume it involves looking at the assembly, but lets just say that isn't my strong suit. If anyone can give a very basic example as to what successful ellision looks like, that would be very useful I won't be using copy ellision just to prettify things, but if I can be guaranteed that it works, it sounds pretty useful.

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• MySQL Integer vs DateTime index

  - by David Kuridža

  Let me start by saying I have looked at many similar questions asked, but all of them relate to Timestamp and DateTime field type without indexing. At least that is my understanding. As we all know, there are certain advantages when it comes to DateTime. Putting them aside for a minute, and assuming table's engine is InnoDB with 10+ million records, which query would perform faster when criteria is based on: DateTime with index int with index In other words, it is better to store date and time as DateTime or UNIX timestamp in int? Keep in mind there is no need for any built-in MySQL functions to be used.

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• When can we mock an object and its methods?

  - by Shailendra

  I am novice to the Moq and unit testing. I have to write unit tests to a lot of classes which has the objects of other classes. can i mock the methods of the class objects. Here is the exact scenerio- I have a class two classes A and B and A has a private object of B and in a method of A i am internally calling the method of B and then doing some calculation and returning the result. Can i mock the method of B in this scenerio? Please try to give me full detail about the conditions where i can mock the methods and functions of the class. Thanx

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• portable way to deal with 64/32 bit time_t

  - by MK

  I have some code which is built both on Windows and Linux. Linux at this point is always 32bit but Windows is 32 and 64bit. Windows wants to have time_t be 64 bit and Linux still has it as 32 bit. I'm fine with that, except in some places time_t values are converted to strings. So when time_T is 32 bit it should be done with %d and when it is 64bit with %lld... what is the smart way to do this? Also: any ideas how I may find all places where time_t's are passed to printf-style functions to address this issue?

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• it is possible to "group by" without losing the original rows?

  - by toPeerOrNotToPeer

  i have a query like this: ID | name | commentsCount 1 | mysql for dummies | 33 2 | mysql beginners guide | 22 SELECT ..., commentsCount // will return 33 for first row, 22 for second one FROM mycontents WHERE name LIKE "%mysql%" also i want to know the total of comments, of all rows: SELECT ..., SUM(commentsCount) AS commentsCountAggregate // should return 55 FROM mycontents WHERE name LIKE "%mysql%" but this one obviously returns a single row with the total. now i want to merge these two queries in one single only, because my actual query is very heavy to execute (it uses boolean full text search, substring offset search, and sadly lot more), then i don't want to execute it twice is there a way to get the total of comments without making the SELECT twice? !! custom functions are welcome !! also variable usage is welcome, i never used them...

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• Putting a variable name = value format in Ruby

  - by Calm Storm

  Hi, I would like to add some debugs for my simple ruby functions and I wrote a function as below, def debug(&block) varname = block.call.to_s puts "#{varname} = #{eval(varname,block)}" end debug {:x} #prints x = 5 debug {:y} #prints y = 5 I understand that eval is evil. So I have two questions. Is there any way to write that debug method without using eval? If NO is there a preferred way to do this? Is there any way to pass a list of arguments to this method? I would ideally prefer debug {:x, :y. :anynumOfvariables}. I could not quite figure out how to factor that into the debug method (i.e, to take a list of arguments)

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• typedef fixed length array

  - by Rajorshi

  Hi, I have to define a 24-bit data type.I am using char[3] to represent the type. Can I typedef char[3] to type24? I tried it in a code sample. I put typedef char[3] type42; in my header file. The compiler did not complain about it. But when I defined a function void foo(type24 val) {} in my C file, it did complain. I would like to be able to define functions like type24_to_int32(type24 val) instead of type24_to_int32(char value[3]).

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• How to keep the first result of a function from Prolog?

  - by zuhakasa

  I need to write a customized function that will be called many times by other fixed functions. In this function, at the first called time, it will return the total number of lines of a file. The second called time of this function, forward, will return the number of lines in small sections of this file. My question is how I keep the first returned result(total number of lines of a file) and use it for the next called times of my function. I need to write or declare any thing only in this function(not in the caller). Something like this: myFunction(Input, MyResult, FirstResult) :- calculateInputFunction(Input, Result), !, MyResult is Result, ... . The problem is, every time myFunction is called, it receives different Input and returns different MyResult. But I would like to keep the first MyResult to use for next called times of myFunction. How can I do that? Thanks very much for your answer in advance.

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• Change a registry value in vb.net

  - by mhofer

  Hello, I have searched a lot to find a solution for my problem, but I can't find any specific solution. I need to change a value which is stored under HKEY_LOCAL_MACHINE\SOFTWARE\APP_NAME. It is not possible to use .NET's registry functions, since they have drastic restrictions. The following snippet should solve my problem: Dim regKey As RegistryKey Dim ver As Decimal regKey = My.Computer.Registry.LocalMachine.OpenSubKey("HKEY_LOCAL_MACHINE\SOFTWARE\APP_NAME", True) regKey.SetValue("IP", "192.168.10.15:18500") regKey.Close() Unfortunately, I get a NullReferenceExeption when I try to set the value. What should I do? I have imported Microsoft.Win32 and RegistryKey doesn't accept any constructor... cheers mike

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• New form on a different thread

  - by Dan

  So I have a thread in my application, which purpose is to listen to messages from the server and act according to what it recieves. I ran into a problem when I wanted to fire off a message from the server, that when the client app recieves it, the client app would open up a new form. However this new form just freezes instantly. I think what's happening is that the new form is loaded up on the same thread as the thread listening to the server, which of course is busy listening on the stream, in turn blocking the thread. Normally, for my other functions in the clients listening thread, I'd use invokes to update the UI of the main form, so I guess what I'm asking for is if here's a way to invoke a new form on the main form.

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• Is there an equivalent to C++'s "friend class" in Java?

  - by Ricket

  In C++ there is a concept of a "friend", which has access to a class's private variables and functions. So if you have: class Foo { friend class Bar; private: int x; } then any instance of the class Bar can modify any Foo instance's x member, despite it being private, because Bar is a friend of Foo. Now I have a situation in Java where this functionality would come in handy. There are three classes: Database, Modifier, Viewer. The Database is just a collection of variables (like a struct). Modifier should be "friends" with Database; that is, it should be able to read and write its variables directly. But Viewer should only be able to read Database's variables. How is this best implemented? Is there a good way to enforce Viewer's read-only access of Database?

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• returning values from function or method multiple times by only calling the class once

  - by Sokhrat Sikar

  I have a members.php file that shows my websites members. I echo members name by using foreach method. A method of Members class returns an array, then I use foreach loop in the members.php file to echo the members. I am trying to aovid writing php code in my members.php file. Is there a way to avoid using foreach inside members.php file? For example, is it possible to return value from a method couple of times? (by only calling the object once). Just like how we normally call the functions? This question doesn't make sense, but I am just trying to see if there is a away around this issue?

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• PHP Datediff days involved

  - by user3549835

  I need to know how many days are involved in a date diff. \For example: <? $start = new DateTime('2014-06-29 14:00:00'); $ende = new DateTime('2014-07-02 05:45:00'); $diff = $start->diff($ende); echo $diff->format('%R'); echo $diff->days; ?> The above code echos +2 My desired result would be 4, because the 29th, 30th, 1st and 2nd of July are "touched". I have no idea to achieve that with the given functions. Coding a day-subtraction seems to bean open door for errors.

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• How to call C++ function from C?

  - by claws

  I know this. Calling C function from C++: If my application was in C++ and I had to call functions from a library written in C. Then I would have used //main.cpp extern "C" void C_library_function(int x, int y);//prototype C_library_function(2,4);// directly using it. This wouldn't mangle the name C_library_function and linker would find the same name in its input *.lib files and problem is solved. Calling C++ function from C??? But here I'm extending a large application which is written in C and I need to use a library which is written in C++. Name mangling of C++ is causing trouble here. Linker is complaining about the unresolved symbols. Well I cannot use C++ compiler over my C project because thats breaking lot of other stuff. What is the way out? By the way I'm using MSVC

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• printf'ing a matrix

  - by Flavius

  I'm trying to implement an all-purpose function for printing 2D data. What I've come up with is: int mprintf(FILE* f, char* fmt, void** data, size_t cols, size_t rows) The challenge is determining how many bits to read at once from data, based on fmt. The format fmt is going to be the stdlib's-specific format for printf() and alike. Do you have any knowledge of already-existing features from stdlibc (GNU GCC C's) I could use to ease this up? I try avoiding having to do it all manually, because I know "I am stupid" (I don't want to introduce stupid bugs). Thus, reusing code would be the bug-freest way. Thanks Addendum I see there's a /usr/include/printf.h. Can't I use any of those functions to do it right and ease my job at the same time?

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• Doubt about a particular pattern of Javascript class definition

  - by fenderplayer

  Recently i saw the following code that creates a class in javascript: var Model.Foo = function(){ // private stuff var a, b; // public properties this.attr1 = ''; this.attr2 = ''; if(Model.Foo._init === 'undefined'){ Model.Foo.prototype = { func1 : function(){ //...}, func2 : function(){ //... }, //other prototype functions } } Model.Foo._init = true; } // Instantiate and use the class as follows: var foo = new Model.Foo(); foo.func1(); I guess the _init variable is used to make sure we don't define the prototypes again. Also, i feel the code is more readable since i am placing everything in a function block (so in oop-speak, all attributes and methods are in one place). Do you see any issues with the code above? Any pitfalls of using this pattern if i need to create lots of classes in a big project?

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• Could someone tell me if my C++ indent style is named? (example given)

  - by Maulrus

  I'm learning C++. For me, my programming style is just what looks the best; it doesn't seem to follow the rules of any one particular style. Here's an example void f(int x){ //no space between close-paren and bracket if (!x){ cout << "x is non-zero\n"; } //closing bracket indented to the same level as the original statement } It's only slightly different for something like a class or a namespace: class myClass {}; //space between class name and bracket, otherwise the same as functions K&R style does uses that kind of bracketing for statements, but my style uses it for everything. I'd like to know if there's a name for it so I can say simply what my indent style is without having to explain using examples like these.

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• Issues with Sinatra and Heroku

  - by Brian Michel

  So I've created and published a Sinatra app to Heroku without any issues. I've even tested it locally with rackup to make sure it functions fine. There are a series of API calls to various places after a zip code is consumed from the URL, but Heroku just wants to tell me there is an server error. I've added an error page that tries to give me more description, however, it tells me it can't perform a `count' for #, which I assume means hash. Here's the code that I thin it's trying to execute... if weather_doc.root.elements["weather"].children.count > 1 curr_temp = weather_doc.root.elements["weather/current_conditions/temp_f"].attributes["data"] else raise error(404, "Not A Valid Zip Code!") end If anyone wants to bang on it, it can be reached at, http://quiet-journey-14.heroku.com/ , but there's not much to be had.

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• Dynamically udpate canvasOverlay property of jQuery jqPlot

  - by You Kuper

  I want to dynamically udpate canvasOverlay property of jQuery jqPlot. This will provide the effect of a timeline in my jqPlot. This effect should be similar to the one shown in this jFiddle. However, instead of drawing points, I want to update canvasOverlay property every second: canvasOverlay: { show: true, objects: [ { rectangle: { xmax: new Date(), xminOffset: "0px", xmaxOffset: "0px", yminOffset: "0px", ymaxOffset: "0px", color: "rgba(0, 0, 0, 0.1)", showTooltip: true } }, ] } How can I do this? What are the functions I should use? UPDATE: My idea is to do something like this: canvasOverlay: { name: 'current', show: true, objects: [ { rectangle: { xmax: new Date(), xminOffset: "0px", xmaxOffset: "0px", yminOffset: "0px", ymaxOffset: "0px", color: "rgba(0, 0, 0, 0.1)", showTooltip: true } }, ] } /... var co = plot.plugins.canvasOverlay; var current = co.get('current'); current.options.objects.rectangle.xmax = new Date(); co.draw(plot);

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• mootools: $ not defined

  - by eaigner

  I've strange error i don't understand. I'm just moving my code from jQuery over to Mootools because it's much cleaner than the jQuery mess. Now when i use the $$('div.canvas') in mootools i get the correct element. When i try $(document).getElement('div.canvas') it tells me that $ is not defined. How can $$ and all helper functions like $lambda etc. be defined but not $? Has something changed there from 1.1 to 1.2 and the docs are not updated yet?

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• Can I replace a method on a jQuery UI object? How?

  - by Cheeso

  If I want to tweak some of the capability of a jQuery UI object, by replacing one of the functions, how would I go about doing that? Example: suppose I wanted to modify the way the jQuery autocomplete widget rendered the suggestions. There's a method on the autocomplete object that looks like this: _renderItem: function( ul, item) { return $( "<li></li>" ) .data( "item.autocomplete", item ) .append( "<a>" + item.label + "</a>" ) .appendTo( ul ); }, Could I replace this? How? What syntax would I use?

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• WinXP Parallels Guest with OS X host -- communication between the two?

  - by Justin

  The setup: Windows XP guest OS running inside Parallels 5 on a OS X 10.6.2 host. I have a win32 application that runs in windows that communicates with other programs by sending out keystrokes to the program in focus. I can run this software inside parallels just fine, but I need a way for it to communicate (via keystrokes) with native OS X applications. For instance, the windows software sends out a continuous stream of a's and w's, based on the program input from an external source. On the other side, I have a Mac version of VLC media player with hotkeys set up for a and w for the two functions I would like to manipulate from the windows software. How can I set up a link between the guest and host OS's with Parallels that lets a windows program send keystrokes to a mac program?

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