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  • Using classes for the first time,help in debugging

    - by kaushik
    here is post my code:this is no the entire code but enough to explain my doubt.please discard any code line which u find irrelavent enter code here saving_tree={} isLeaf=False class tree: global saving_tree rootNode=None lispTree=None def __init__(self,x): file=x string=file.readlines() #print string self.lispTree=S_expression(string) self.rootNode=BinaryDecisionNode(0,'Root',self.lispTree) class BinaryDecisionNode: global saving_tree def __init__(self,ind,name,lispTree,parent=None): self.parent=parent nodes=lispTree.getNodes(ind) print nodes self.isLeaf=(nodes[0]==1) nodes=nodes[1]#Nodes are stored self.name=name self.children=[] if self.isLeaf: #Leaf Node print nodes #Set the leaf data self.attribute=nodes print "LeafNode is ",nodes else: #Set the question self.attribute=lispTree.getString(nodes[0]) self.attribute=self.attribute.split() print "Question: ",self.attribute,self.name tree={} tree={str(self.name):self.attribute} saving_tree=tree #Add the children for i in range(1,len(nodes)):#Since node 0 is a question # print "Adding child ",nodes[i]," who has ",len(nodes)-1," siblings" self.children.append(BinaryDecisionNode(nodes[i],self.name+str(i),lispTree,self)) print saving_tree i wanted to save some data in saving_tree{},which i have declared previously and want to use that saving tree in the another function outside the class.when i asked to print saving_tree it printing but,only for that instance.i want the saving_tree{} to have the data to store data of all instance and access it outside. when i asked for print saving_tree outside the class it prints empty{}.. please tell me the required modification to get my required output and use saving_tree{} outside the class..

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  • create CLLocationCoordinate2D from array

    - by shani
    I have a plist with dictionary of array's with coordinates (stored as strings). I want to create a CLLocationCoordinate2D from every array and crate an overlay for the map. I did that - NSString *thePath = [[NSBundle mainBundle] pathForResource:@"Roots" ofType:@"plist"]; NSDictionary *pointsDic = [[NSDictionary alloc] initWithContentsOfFile:thePath]; NSArray *pointsArray = [NSArray arrayWithArray:[pointsDic objectForKey:@"roade1"]]; CLLocationCoordinate2D pointsToUse[256]; for(int i = 0; i < 256; i++) { CGPoint p = CGPointFromString([pointsArray objectAtIndex:i]); pointsToUse[i] = CLLocationCoordinate2DMake(p.x,p.y); NSLog(@"coord %f",pointsToUse [i].longitude); NSLog(@"coord %f",pointsToUse [i].latitude); } MKPolyline *myPolyline = [MKPolyline polylineWithCoordinates:pointsToUse count:256]; [[self mv] addOverlay:myPolyline]; but the app is crashing without any error. (BTW when i remove the addOverLay method the app does not crash). I have 2 questions- What am i doing wrong? I have tried to set the pointsArray count as the argument for the CLLocationCoordinate2D like that - CLLocationCoordinate2D pointsToUse[pointsArray count]; And i am getting an error. How can i set the CLLocationCoordinate2D dynamically ? Thanks for any help. Shani

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  • Unsure how to come up with a good design

    - by Mewzer
    Hello there, I am having trouble coming up with a good design for a group of classes and was hoping that someone could give me some guidance on best practices. I have kept the classes and member functions generic to make the problem simpler. Essentially, I have three classes (lets call them A, B, and C) as follows: class A { ... int GetX( void ) const { return x; }; int GetY( void ) const { return y; }; private: B b; // NOTE: A "has-a" B int x; int y; }; class B { ... void SetZ( int value ) { z = value }; private: int z; C c; // NOTE: B "has-a" C }; class C { private: ... void DoSomething(int x, int y){ ... }; void DoSomethingElse( int z ){ ... }; }; My problem is as follows: Class A uses its member variables "x" and "y" a lot internally. Class B uses its member variable "z" a lot internally. Class B needs to call C::DoSomething(), but C::DoSomething() needs the values of X and Y in class A passed in as arguments. C::DoSomethingElse() is called from say another class (e.g. D), but it needs to invoke SetZ() in class B!. As you can see, it is a bit of a mess as all the classes need information from one another!. Are there any design patterns I can use?. Any ideas would be much appreciated ....

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  • Getting a stream back from a .Net remoting service that is accessible with IP v4 and v6

    - by jon.ediger
    My company has an existing .Net Remoting service that listens on a port, fronting interfaces used by external systems. This all works great with IP v4 based communications. However, this service now needs to support both IP v4 communications and IP v6 communications. I have found info that the system.runtime.remoting section of the app.config should include two channels as follows: <channel ref="tcp" name="tcp6" port="9000" bindTo="[::]" /> <channel ref="tcp" name="tcp4" port="9000" bindTo="0.0.0.0" /> The above config file changes to the System.Runtime.Remoting config section will get the remoting service responding to non-stream functions on both ip v4 and ip v6. The issue comes only when attempting to get a stream back, used to upload or download large files. In this case, instead of getting a usable stream back, the following ArgumentException is thrown instead: IPv4 address 0.0.0.0 and IPv6 address ::0 are unspecified addresses that cannot be used as a target address. Parameter name: hostNameOrAddress Is there a way to modify the app.config (in the system.runtime.remoting section, or another section) so that the service will return a stream mapped to a real ip so the client can actually upload/download files while maintaining the ability to use both IP v4 and IP v6?

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  • understanding and implementing Boids

    - by alphablender
    So I'm working on porting Boids to Brightscript, based on the pseudocode here: http://www.kfish.org/boids/pseudocode.html I'm trying to understand the data structures involved, for example is Velocity a single value, or is it a 3D value, ie velocity={x,y,z} It seems as if the pseudocode seems to mix this up where sometimes it has an equation that incudes both vectors and single-value items: v1 = rule1(b) v2 = rule2(b) v3 = rule3(b) b.velocity = b.velocity + v1 + v2 + v3 If Velocity is a tripartite value then this would make sense, but I'm not sure. So my first question here is, is this the correct datastructure for a single boid based on the Pseudocode on that page: boid={position:{px:0,py:0,pz:0},velocity:{x:0,y:0,z:0},vector:{x:0,y:0,z:0},pc:{x:0,y:0,z:0},pv:{x:0,y:0,z:0}) where pc=perceived center, pv= perceived velocity I"ve implemented a vector_add, vector_sub, vector_div, and vector boolean functions. The reason I'm starting from this pseudocode is I've not been able to find anything else that is as readable, but it still leaves me with lots of questions as the data structures are not explicitly defined for each variable. (edit) here's a good example of what i'm talking about: IF |b.position - bJ.position| < 100 THEN if b.position - b[j].position are both 3D coordinates, how can they be considered "less than 100" unless they are < {100,100,100} ? Maybe that is what I need to do here, use a vector comparison function?

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  • need help with C++ using maps to keep track of words in a INPUT file

    - by eNetik
    Let say i have a text file with today is today but tomorrow is today tomorrow then using maps how can i keep track of the words that are repeated? and on which line it repeats? so far i have each string in the file read in as a temp and it is stored in the following way: map<string,int> storage; int count = 1 // for the first line of the file if(infile.is_open()){ while( !infile.eof() ){ getline(in, line); istringstream my_string(line); while(my_string.good()){ string temp; my_string >> temp; storage[temp] = count } count++;// so that every string read in the next line will be recorded as that line. } } map<string,int>::iterator m; for(int m = storage.begin(); m!= storage.end(); m++){ out<<m->first<<": "<<"line "<<m->second<<endl; } right now the output is just but: line 1 is: line 2 today: line 2 tomorrow: line 2 But instead.. it should print out(no repeating strings): today : line 1 occurred 2 times, line 2 occurred 1 time. is: line 1 occurred 1 time, line 2 occurred 1 time. but: line 1 occurred 1 time. tomorrow: line 2 occurred 2 times. Note: the order of the string does not matter. Any help would be appreciated. Thanks.

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  • Security benefits from a second opinion, are there flaws in my plan to hash & salt user passwords vi

    - by Tchalvak
    Here is my plan, and goals: Overall Goals: Security with a certain amount of simplicity & database-to-database transferrability, 'cause I'm no expert and could mess it up and I don't want to have to ask a lot of users to reset their passwords. Easy to wipe the passwords for publishing a "wiped" databased of test data. (e.g. I'd like to be able to use a postgresql statement to simply reset all passwords to something simple so that testers can use that testing data for themselves). Plan: Hashing the passwords Account creation records the original email that an account is created with, forever. A global salt is used, e.g. "90fb16b6901dfceb73781ba4d8585f0503ac9391". An account specific salt, the original email the account was created with, is used, e.g. "[email protected]". The users's password is used, e.g. "password123" (I'll be warning against weak passwords in the signup form) The combination of the global salt, account specific salt, and password is hashed via some hashing method in postgresql (haven't been able to find documentation for hashing functions in postgresql, but being able to use sha-2 or something like that would be nice if I could find it). The hash gets stored in the database. Recovering an account To change their password, they have to go through standard password reset (and that reset email gets sent to the original email as well as the most recent account email that they have set). Flaws? Are there any flaws with this that I need to address? And are there best practices to doing hashing fully within postgresql?

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  • WCF - Return object without serializing?

    - by Mayo
    One of my WCF functions returns an object that has a member variable of a type from another library that is beyond my control. I cannot decorate that library's classes. In fact, I cannot even use DataContractSurrogate because the library's classes have private member variables that are essential to operation (i.e. if I return the object without those private member variables, the public properties throw exceptions). If I say that interoperability for this particular method is not needed (at least until the owners of this library can revise to make their objects serializable), is it possible for me to use WCF to return this object such that it can at least be consumed by a .NET client? How do I go about doing that? Update: I am adding pseudo code below... // My code, I have control [DataContract] public class MyObject { private TheirObject theirObject; [DataMember] public int SomeNumber { get { return theirObject.SomeNumber; } // public property exposed private set { } } } // Their code, I have no control public class TheirObject { private TheirOtherObject theirOtherObject; public int SomeNumber { get { return theirOtherObject.SomeOtherProperty; } set { // ... } } } I've tried adding DataMember to my instance of their object, making it public, using a DataContractSurrogate, and even manually streaming the object. In all cases, I get some error that eventually leads back to their object not being explicitly serializable.

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  • Design Advice Needed For Synonyms Database

    - by James J
    I'm planning to put together a database that can be used to query synonyms of words. The database will end up huge, so the idea is to keep things running fast. I've been thinking about how to do this, but my database design skills are not up to scratch these days. My initial idea was to have each word stored in one table, and then another table with a 1 to many relationship where each word can be linked to another word and that table can be queried. The application I'm developing allows users to highlight a word, and then type in, or select some synonyms from the database for that word. The application learns from the user input so if someone highlights "car" and types in "motor" the database would be updated to link the relationship if it don't exist already. What I don't want to happen is for a user to type in the word "shop" and link it to the word car. So I'm thinking I will need to add some sort of weight to each relationship. Eventually the synonyms the users enter will be used so they can auto select common synonyms used with a certain word. The lower weight words will not be displayed so shop could never be a synonym of car unless it had a very high weight, and chances are nobody is going to do that. Does the above sound right? Can you offer any suggestions or improvements?

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  • Pthread - setting scheduler parameters

    - by Andna
    I wanted to use read-writer locks from pthread library in a way, that writers have priority over readers. I read in my man pages that If the Thread Execution Scheduling option is supported, and the threads involved in the lock are executing with the scheduling policies SCHED_FIFO or SCHED_RR, the calling thread shall not acquire the lock if a writer holds the lock or if writers of higher or equal priority are blocked on the lock; otherwise, the calling thread shall acquire the lock. so I wrote small function that sets up thread scheduling options. void thread_set_up(int _thread) { struct sched_param *_param=malloc(sizeof (struct sched_param)); int *c=malloc(sizeof(int)); *c=sched_get_priority_min(SCHED_FIFO)+1; _param->__sched_priority=*c; long *a=malloc(sizeof(long)); *a=syscall(SYS_gettid); int *b=malloc(sizeof(int)); *b=SCHED_FIFO; if (pthread_setschedparam(*a,*b,_param) == -1) { //depending on which thread calls this functions, few thing can happen if (_thread == MAIN_THREAD) client_cleanup(); else if (_thread==ACCEPT_THREAD) { pthread_kill(params.main_thread_id,SIGINT); pthread_exit(NULL); } } } sorry for those a,b,c but I tried to malloc everything, still I get SIGSEGV on the call to pthread_setschedparam, I am wondering why?

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  • Convert C# (with typed events) to VB.NET

    - by Steven
    I have an ASPX page (with VB Codebehind). I would like to extend the GridView class to show the header / footer when no rows are returned. I found a C# example online (link) (source). However, I cannot convert it to VB because it uses typed events (which are not legal in VB). I have tried several free C# to VB.NET converters online, but none have worked. Please convert the example to VB.NET or provide an alternate method of extending the GridView class. Notes / Difficulties: If you get an error with DataView objects, specify the type as System.Data.DataView and the type comparison could be the following: If data.[GetType]() Is GetType(System.Data.DataView) Then Since the event MustAddARow cannot have a type in VB (and RaiseEvent event doesn't have a return value), how can I compare it to Nothing in the function OnMustAddARow()? EDIT: The following is a sample with (hopefully) relevant code to help answer the question. namespace AlwaysShowHeaderFooter { public delegate IEnumerable MustAddARowHandler(IEnumerable data); public class GridViewAlwaysShow : GridView { ////////////////////////////////////// // Various member functions omitted // ////////////////////////////////////// protected IEnumerable OnMustAddARow(IEnumerable data) { if (MustAddARow == null) { throw new NullReferenceException("The datasource has no rows. You must handle the \"MustAddARow\" Event."); } return MustAddARow(data); } public event MustAddARowHandler MustAddARow; } }

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  • php import larg table to phpmyadmin database

    - by safaali
    hi, I am so worry :( I dropped one of the tables from the database accidentally. fortunately, I have back-up. (I have used the "Auto backup for mysql") The back-up of the table is stored as .txt file (56 Megabytes) on my PC. I tried to import it by PhpMyAdmin and the import failed because the file is too large to import. then I uploaded the file to /home/tablebk directory. I have some experiences in php. I know that I would import it with this code, but i don't know the sql statment for this import. what is have to put as $line variable? please help me :( :( <?php $dbhost = 'localhost'; $dbuser = 'mysite'; $dbpw = 'password'; $dbname = 'databasename'; $file = @fopen('country.txt', 'r'); if ($file) { while (!feof($file)) { $line = trim(fgets($file)); $flag = mysql_query($line); if (isset($flag)) { echo 'Insert Successfully<br />'; } else { echo mysql_error() . '<br/>'; } flush(); } fclose($file); } echo '<br />End of File'; ?>

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  • get random password with puppet function

    - by ninja-2
    I have a function that allow me to generate random password. My function is working well without a puppetmaster. When i tried with a master an error appear when I called the function : Error 400 on SERVER: bad value for range Here is my function module Puppet::Parser::Functions newfunction(:get_random_password, :type => :rvalue, :doc => <<-EOS Returns a random password. EOS ) do |args| raise(Puppet::ParseError, "get_random_password(): Wrong number of arguments " + "given (#{args.size} for 1)") if args.size != 1 specials = ((33..33).to_a + (35..38).to_a + (40..47).to_a + (58..64).to_a + (91..93).to_a + (95..96).to_a + (123..125).to_a).pack('U*').chars.to_a numbers = (0..9).to_a alphal = ('a'..'z').to_a alphau = ('A'..'Z').to_a length = args[0] CHARS = (alphal + specials + numbers + alphau) pwd = CHARS.sort_by { rand }.join[0...length] return pwd end end The function is called in both case with $pwd = get_random_password(10). When I specified the length directly in the function to 10 for example. the password is well generated in master mode. Have you any idea why i can't specify the lentgth value ? Thanks for any help.

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  • choose javascript variable based on element id from jquery

    - by phoffer
    I feel like this is a simple question, but I am still relatively new to javascript and jquery. I am developing a site for a touch interface that uses unordered lists and jquery .click functions to take input data. I have a section to input a m:ss time, with 3 divs, each containing a list of digits for time. I need to get the input for each column and set it as a variable. I originally designed the inputs to change form inputs, because I didn't understand javascript very much. It was easy to change the 3 hidden inputs by using div id's, but I can't figure out how to do it now with javascript variables. Here is my original jquery code... $("div#time>div>ul>li").click(function() { var id = $(this).parents(".time").attr("name"); var number = $(this).html(); $("input#"+id).val(number); }); The last line sets one of 3 hidden inputs equal to whatever was clicked. I need to make it so separate variables take the inputs, then I can manipulate those variables however I want. Here's a short snippet of the html, to have an idea of how jquery grabs it. <div id="time"> <h1>Time</h1> <div name="minute" class="time" id="t_minute"> M : <ul> The full time html is here: link text Thanks everyone! I've been using SO to answer many questions I've had, but I couldn't find something for this, so I figured I would join, since I'm sure I will have more questions along the way.

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  • JMS message. Model to include data or pointers to data?

    - by John
    I am trying to resolve a design difference of opinion where neither of us has experience with JMS. We want to use JMS to communicate between a j2ee application and the stand-alone application when a new event occurs. We would be using a single point-to-point queue. Both sides are Java-based. The question is whether to send the event data itself in the JMS message body or to send a pointer to the data so that the stand-alone program can retrieve it. Details below. I have a j2ee application that supports data entry of new and updated persons and related events. The person records and associated events are written to an Oracle database. There are also stand-alone, separate programs that contribute new person and event records to the database. When a new event occurs through any of 5-10 different application functions, I need to notify remote systems through an outbound interface using an industry-specific standard messaging protocol. The outbound interface has been designed as a stand-alone application to support scalability through asynchronous operation and by moving it to a separate server. The j2ee application currently has most of the data in memory at the time the event is entered. The data would consist of approximately 6 different objects; a person object and some with multiple instances for an average size in the range of 3000 to 20,000 bytes. Some special cases could be many times this amount. From a performance and reliability perspective, should I model the JMS message to pass all the data needed to create the interface message, or model the JMS message to contain record keys for the data and have the stand-alone Java application retrieve the data to create the interface message?

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  • Adding variably named fields to Python classes

    - by Carson Myers
    I have a python class, and I need to add an arbitrary number of arbitrarily long lists to it. The names of the lists I need to add are also arbitrary. For example, in PHP, I would do this: class MyClass { } $c = new MyClass(); $n = "hello" $c.$n = array(1, 2, 3); How do I do this in Python? I'm also wondering if this is a reasonable thing to do. The alternative would be to create a dict of lists in the class, but since the number and size of the lists is arbitrary, I was worried there might be a performance hit from this. If you are wondering what I'm trying to accomplish, I'm writing a super-lightweight script interpreter. The interpreter walks through a human-written list and creates some kind of byte-code. The byte-code of each function will be stored as a list named after the function in an "app" class. I'm curious to hear any other suggestions on how to do this as well.

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  • What is the best way to implement a callback scenario using WCF and ASP.NET MVC?

    - by Mark Struzinski
    I am new to WCF. I just finished reading Learning WCF and I think I've got a pretty good grasp of the fundamentals. I am adding functionality to a line of business app that runs on ASP.NET MVC entirely inside the corporate LAN. I am calling into a service that will also send me events as they occur (and not as responses to service calls). These events can occur at any point during the user's session. I have the service written, and it is able to pick up these events. What would be the best way to deliver these events to the user? My initial thought is to run the WCF service in duplex mode over net TCP and implement the events as callbacks. Using this scenario, the best way I can think up to deliver the events to the user is a dictionary object stored in the session. The dictionary would be populated by the callbacks and polled on a set frequency for delivery via AJAX calls. Has anyone dealt with this scenario? Is there a more efficient way to implement this?

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  • How security of the systems might be improved using database procedures?

    - by Centurion
    The usage of Oracle PL/SQL procedures for controlling access to data often emphasized in PL/SQL books and other sources as being more secure approach. I'v seen several systems where all business logic related with data is performed through packages, procedures and functions, so application code becomes quite "dumb" and is only responsible for visualization part. I even heard some devs call such approaches and driving architects as database nazi :) because all logic code resides in database. I do know about DB procedure performance benefits, but now I'm interested in a "better security" when using thick client model. I assume such design mostly used when Oracle (and maybe MS SQL Server) databases are used. I do agree such approach improves security but only if there are not much users and every system user has a database account, so we might control and monitor data access through standard database user security. However, how such approach could increase the security for an average web system where thick clients are used: for example one database user with DML grants on all tables, and other users are handled using "users" and"user_rights" tables? We could use DB procedures, save usernames into context use that for filtering but vulnerability resides at the root - if the main database account is compromised than nothing will help. Of course in a real system we might consider at least several main users (for example frontend_db_user, backend_db_user).

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  • Does std::vector change its address? How to avoid

    - by kunigami
    Since vector elements are stored contiguously, I guess it may not have the same address after some push_back's , because the initial allocated space could not suffice. I'm working on a code where I need a reference to an element in a vector, like: int main(){ vector<int> v; v.push_back(1); int *ptr = &v[0]; for(int i=2; i<100; i++) v.push_back(i); cout << *ptr << endl; //? return 0; } But it's not necessarily true that ptr contains a reference to v[0], right? How would be a good way to guarantee it? My first idea would be to use a vector of pointers and dynamic allocation. I'm wondering if there's an easier way to do that? PS.: Actually I'm using a vector of a class instead of int, but I think the issues are the same.

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  • Java Equivalent of C++ .dll?

    - by Matt D
    So, I've been programming for a while now, but since I haven't worked on many larger, modular projects, I haven't come across this issue before. I know what a .dll is in C++, and how they are used. But every time I've seen similar things in Java, they've always been packaged with source code. For instance, what would I do if I wanted to give a Java library to someone else, but not expose the source code? Instead of the source, I would just give a library as well as a Javadoc, or something along those lines, with the public methods/functions, to another programmer who could then implement them in their own Java code. For instance, if I wanted to create a SAX parser that could be "borrowed" by another programmer, but (for some reason--can't think of one in this specific example lol) I don't want to expose my source. Maybe there's a login involved that I don't want exploited--I don't know. But what would be the Java way of doing this? With C++, .dll files make it much easier, but I have never run into a Java equivalent so far. (I'm pretty new to Java, and a pretty new "real-world" programmer, in general as well)

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  • Determining presence of prototype with correct return type

    - by R..
    Here's a random problem in C black magic I just came up with: Write a function that returns 1 if malloc has been prototyped to return a pointer type and 0 if malloc has a return type of int (either implicitly or due to wrong prototype), without invoking any implementation-defined or undefined behavior. I believe it's solvable, but I haven't worked out the solution. Note that calling the function cannot be necessary and in fact is not possible since calling a function with the incorrect prototype is undefined behavior. I have some ideas for ingredients but I think it makes for a better puzzle (and possibly more diverse ideas) if I leave them out for now. I don't need the solution for any immediate use, but it could be handy in configure scripts and such. Update: A better example of the usefulness (with strdup instead of malloc): #undef strdup #define strdup(x) (strdup_has_proto ? strdup((x)) : my_strdup((x))) i.e. being able to implement X_has_proto as an expression at the source level could be a portable way to use functions which a system might or might not have, and fall back on a local replacement, without needing any separate configure step.

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  • (Python/Pyramid) Better ways to have standard list/form editors?

    - by badcat
    I'm working on a number of Pyramid (former Pylons) projects, and often I have the need to display a list of some content (let's say user accounts, log entries or simply some other data). A user should be able to paginate through the list, click on a row and get a form where he/she can edit the contents of that row. Right now I'm always re-inventing the wheel by having Mako templates which use webhelpers for the pagination, Jquery UI for providing a dialog and I craft the editor form and AJAX requests on the client and server side by hand. As you may know, this eats up painfully much time. So what I'm wondering is: Is there a better way of providing lists, editor dialog and server/client communication about this, without having to re-invent the wheel every time? I heard Django takes off a big load of that by providing user accounts and other stuff out of the box; but in my case it's not just about user accounts, it can be any kind of data that is stored on the server-side in a SQL database, which should be able to be edited by a user. Thanks in advance!

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  • How to combine two rows and calculate the time difference between two timestamp values in MySQL?

    - by Nadar
    I have a situation that I'm sure is quite common and it's really bothering me that I can't figure out how to do it or what to search for to find a relevant example/solution. I'm relatively new to MySQL (have been using MSSQL and PostgreSQL earlier) and every approach I can think of is blocked by some feature lacking in MySQL. I have a "log" table that simply lists many different events with their timestamp (stored as datetime type). There's lots of data and columns in the table not relevant to this problem, so lets say we have a simple table like this: CREATE TABLE log ( id INT NOT NULL AUTO_INCREMENT, name VARCHAR(16), ts DATETIME NOT NULL, eventtype VARCHAR(25), PRIMARY KEY (id) ) Let's say that some rows have an eventtype = 'start' and others have an eventtype = 'stop'. What I want to do is to somehow couple each "startrow" with each "stoprow" and find the time difference between the two (and then sum the durations per each name, but that's not where the problem lies). Each "start" event should have a corresponding "stop" event occuring at some stage later then the "start" event, but because of problems/bugs/crashed with the data collector it could be that some are missing. In that case I would like to disregard the event without a "partner". That means that given the data: foo, 2010-06-10 19:45, start foo, 2010-06-10 19:47, start foo, 2010-06-10 20:13, stop ..I would like to just disregard the 19:45 start event and not just get two result rows both using the 20:13 stop event as the stop time. I've tried to join the table with itself in different ways, but the key problems for me seems to be to find a way to correctly identify the corresponding "stop" event to the "start" event for the given "name". The problem is exactly the same as you would have if you had table with employees stamping in and out of work and wanted to find out how much they actually were at work. I'm sure there must be well known solutions to this, but I can't seem to find them...

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  • Implementing comparision operators via 'tuple' and 'tie', a good idea?

    - by Xeo
    (Note: tuple and tie can be taken from Boost or C++11.) When writing small structs with only two elements, I sometimes tend to choose a std::pair, as all important stuff is already done for that datatype, like operator< for strict-weak-ordering. The downsides though are the pretty much useless variable names. Even if I myself created that typedef, I won't remember 2 days later what first and what second exactly was, especially if they are both of the same type. This gets even worse for more than two members, as nesting pairs pretty much sucks. The other option for that is a tuple, either from Boost or C++11, but that doesn't really look any nicer and clearer. So I go back to writing the structs myself, including any needed comparision operators. Since especially the operator< can be quite cumbersome, I thought of circumventing this whole mess by just relying on the operations defined for tuple: Example of operator<, e.g. for strict-weak-ordering: bool operator<(MyStruct const& lhs, MyStruct const& rhs){ return std::tie(lhs.one_member, lhs.another, lhs.yet_more) < std::tie(rhs.one_member, rhs.another, rhs.yet_more); } (tie makes a tuple of T& references from the passed arguments.) Edit: The suggestion from @DeadMG to privately inherit from tuple isn't a bad one, but it got quite some drawbacks: If the operators are free-standing (possibly friends), I need to inherit publicly With casting, my functions / operators (operator= specifically) can be easily bypassed With the tie solution, I can leave out certain members if they don't matter for the ordering Are there any drawbacks in this implementation that I need to consider?

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  • c++ code cons/pros

    - by VirusEcks
    below i have a code that runs in most of my simple programs .. . i want to know if it's good/bad ... and cons/pros . . win32 header file: win32.h #include <windows.h> #include <process.h> #include <stdarg.h> main header file: inc.h #include "win32.h" #ifndef INCS #define INCS #define DD #else #define DD extern #endif #ifndef VARS #define titlen L"my program" #endif DD wchar_t gtitle[512]; DD wchar_t gclass[512]; DD wchar_t gdir[32767]; #include "resources.h" #include "commonfunctions.h" then all files have something like this commonfunctions.h DD inline bool icmp( const char *String1, const char *String2 ) { if ( _stricmp( String1, String2 ) == 0 ) { return true; } return false; } DD inline bool scmp( const char *String1, const char *String2 ) { if ( strcmp( String1, String2 ) == 0 ) { return true; } return false; } all global variables have DD infront of them and all functions have DD too . is there a bad side of this ? . i came up with this idea and it wasn't problematic at all in small programs . but before i apply it in a large project will it be problematic ?. thanks in advance.

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