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  • Performing LINQ Self Join

    - by senfo
    I'm not getting the results I want for a query I'm writing in LINQ using the following: var config = (from ic in repository.Fetch() join oc in repository.Fetch() on ic.Slot equals oc.Slot where ic.Description == "Input" && oc.Description == "Output" select new Config { InputOid = ic.Oid, OutputOid = oc.Oid }).Distinct(); The following SQL returns 53 rows (which is correct), but the above LINQ returns 96 rows: SELECT DISTINCT ic.Oid AS InputOid, oc.Oid AS OutputOid FROM dbo.Config AS ic INNER JOIN dbo.Config AS oc ON ic.Slot = oc.Slot WHERE ic.Description = 'Input' AND oc.Description = 'Output' How would I replicate the above SQL in a LINQ query? Update: I don't think it matters, but I'm working with LINQ to Entities 4.0.

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  • Private heap or manage memory self

    - by Max
    Hello all, I know we could take some advantages from creating private heap of Windows especially for frequently allocated and de-allocated small chunks. But I think the normal approach is to allocate a large memory from default heap and manage the allocations and de-allocations ourselves. My question is which way is advantages and disadvantage between those two ways? Thanks, Max

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  • C++: why a self pointer of a struct automatically changes to void*

    - by Stone
    struct ptr{ int node; ptr *next; ptr(){} ptr(int _node, ptr *_next){ node=_node; next=_next; } }; struct list_t{ ptr *sht; int size; void push(int node){ size++; sht=new ptr(node,sht); } }shthead[100001], comp[200001], tree[200001]; The struct ptr is a smart pointer, be used as a linked list. But when I debug the code in gdb, I found that the ptr*'s were all converted to void*. GDB output: (gdb) pt ptr type = struct ptr { int node; void *next; public: ptr(void); ptr(int, void *); } However, I can still see the data of the struct if I covert them back to ptr* in gdb. What's the reason for this please?

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  • What programming languages do you consider indispensable in your experience?

    - by Federico Ramponi
    Each programming language comes with its concepts, best practices, libraries, tools, community, in one word: culture. Learning more than one programming language will make you a better programmer, for the more concepts you learn, the faster you will feel comfortable when the next language or technology will come. Mine, so far, are C, some C++, and Python, and many times I read that it would be worth learning LISP, for "the profound enlightenment experience you will have when you finally get it" (quoting Eric Raymond). My questions are: Which is the next one you would consider a good investment to learn? Of the many programming languages you have learnt and worked with, which ones do you consider to be an essential part of one's CS culture, and why? EDIT. Further question: is there any language you would sincerely advise to avoid as a waste of time? (The famous, and questionable, slatings in this letter from Dijkstra come to my mind.)

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  • How to pickle and unpickle objects with self-references and from a class with slots?

    - by EOL
    Is it possible to pickle an object from a class with slots, when this object references itself through one of its attributes? Here is a simple example: import weakref import pickle class my_class(object): __slots__ = ('an_int', 'ref_to_self', '__weakref__') def __init__(self): self.an_int = 42 self.ref_to_self = weakref.WeakKeyDictionary({self: 1}) # __getstate__ and __setstate__ not defined: how should this be done? if __name__ == '__main__': obj = my_class() # How to make the following work? obj_pickled = pickle.dumps(obj) obj_unpickled = pickle.loads(obj_pickled) # Self-references should be kept: print "OK?", obj_unpickled == obj_unpickled.ref_to_self.keys()[0]

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  • hierarchical data from self referencing table in tree form

    - by Beta033
    It looks like this has been asked and answered in all the simple cases, excluding the one that I'm having trouble with. I've tried using a recursive CTE to generate this; however maybe a cursor would be better? Or maybe a set of recursive functions will do the trick? Can this be done in a cte? consider the following table PrimaryKey ParentKey 1 NULL 2 1 3 6 4 7 5 2 6 1 7 NULL should yield PK 1 -2 --5 -6 --3 7 -4 where the number of - marks equal the depth, my primary difficulty is the ordering.

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  • Question about C Pointers (just learning)

    - by Mike
    I am curious as to why this is an error and what the error message means. Here is some code. int *x[] = {"foo", "bar", "baz"}; int *y[] = {"foo", "bar", "baz"}; x = y; I try to compile and I get this: error: incompatible types when assigning to type ‘char [3]’ from type ‘char *’ Question #1 why is this an error? and Question #2 why are the types different? Thanks for you help.

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  • Learning to work with audio in C++

    - by Skilldrick
    My degree was in audio engineering, but I'm fairly new to programming. I'd like to learn how to work with audio in a programming environment, partly so I can learn C++ better through interesting projects. First off, is C++ the right language for this? Is there any reason I shouldn't be using it? I've heard of Soundfile and some other libraries - what would you recommend? Finally, does anyone know of any good tutorials in this subject? I've learnt the basics of DSP - I just want to program it! EDIT: I use Windows. I'd like to play about with real-time stuff, a bit like Max/MSP but with more control.

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  • SQL database self interaction entity

    - by Ricardo Costa
    I've been working on a database, wich is referent to an Aeroport management. I'm having a problem that it's freaking me out.. What i'm trying to do is, assuming that a client wants to know the distance between 2 locations, in miles or kms. As an example, if the user wants to know the distance between London and Amsterdam, should that distance be calculated by a formule or should it be already stored on the database? (1,N) ____________ ____________|__ | | | | | City/Airport |<---------| |______________| How can i show to user the distance between his 2 choices? RicardoCosta

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  • LINQ2SQL: How to let a column accept null values as zero (0) in Self-Relation table

    - by Remon
    As described in the img, I got a parent-Children relation and since the ParentID not accepting null values (and I can't change to nullabel due to some restriction in the UI I have), how can I remove an existence relation between ReportDataSources in order to change the parent for them (here i want to set the parentId for one of them = 0) how could i do that since i cant change the ParentID directly and setting Parent = null is not valid public void SetReportDataSourceAsMaster(ReportDataSource reportDataSource) { //Some logic - not necessarily for this scenario //Reset Master this.ReportDataSources.ToList().ForEach(rds => rds.IsMaster = false); //Set Master reportDataSource.IsMaster = true; //Set Parent ID for the rest of the Reports data sources this.ReportDataSources.Where(rds => rds.ID != reportDataSource.ID).ToList().ForEach(rds => { //Change Parent ID rds.Parent = reportDataSource; //Remove filttering data rds.FilteringDataMembers.Clear(); //Remove Grouping Data rds.GroupingDataMembers.Clear(); }); //Delete parent HERE THE EXCEPTION THROWN AFTER CALLING SUBMITCHANGES() reportDataSource.Parent = null; //Other logic } Exception thrown after calling submitChanges An attempt was made to remove a relationship between a ReportDataSource and a ReportDataSource. However, one of the relationship's foreign keys (ReportDataSource.ParentID) cannot be set to null.

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  • Self-contained python installation with executable tools included (pip, orbited, etc)

    - by Tristan
    I'm trying deploy a Python application on Windows as a folder that includes a full python 2.6 folder. I don't need/want a fancy solution like py2exe, I'm just trying to automate deployment of a web application. So long as I include python26.dll and set the PYTHONHOME correctly, things seem to work if I just include the Python26 folder in its entirety. However a number of the Python26/Script files don't work. For instance, pip.exe, orbited.exe, and morbid.exe all do nothing (complete with no output) when I try to run them on a system that doesn't have a real Python26 installation. I've run out of ideas. Suggestions?

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  • self join table

    - by San82moon
    HI, i have a table, new_id----old_id----created_on 1234------5678------20100912 5678------3456------20100808 etc. i wrote this query, $q = "select event1.new_id, event1.old_id, event1.created_on,event2.new_id, event2.old_id, event2.created_on FROM replaced_isbns event1 JOIN replaced_isbns event2 ON event2.new_id = event1.old_id WHERE event1.new_id='$id'"; but i get result as 5678 - 1234, ie only one row, i want all rows... plz help me. Thanks, SLC

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  • Looking for resources for learning SharePoint Foundation on the Internet

    - by Kabeer
    Hello. While I am quite comfortable with the .Net world, I am a baby as far as SharePoint technologies are concerned. With the advent of SharePoint 2010 (Foundation especially), I'd like to directly learn the new version. However, I am not getting enough resources on the Internet that can be helpful. Besides knowing to maneuver a SharePoint site, I'd like to understand stuff under the hood from the architecture standpoint and subsequently the APIs. Can the community please guide me to the most suitable resource(s) available on the Internet?

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  • Self-modify the classpath within a Scala script?

    - by Alex R
    I'm trying to replace a bunch of Linux shell scripts with Scala scripts. One of the remaining challenges is how to scan an entire directory of JARs and place them into the classpath. Currently this is done in the shell script prior to invoking the scala JVM. I'd like to eliminate the shell script completely. Is there an elegant scala idiom for this? I have found this other question but in Java it seems hardly worthwhile to mess with it: http://stackoverflow.com/questions/252893/how-do-you-change-the-classpath-within-java

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  • MySQL on two ports using IPTables - self-access

    - by b0rman
    I trying to make MySQL available by 2 ports: 3306 and 3339 I added rule to iptables: iptables -t nat -A PREROUTING -i bond0 -p tcp --dport 3339 -j REDIRECT --to-port 3306 and everythin is great for remote connections. But if I'm trying to connect it locally, I'm getting an error: mysql -u username -ppassword --port=3339 -h Host.Name ERROR 2003 (HY000): Can't connect to MySQL server on 'Host.Name' (111) Any ideas how can I edit iptables to get local access via 3339 port?

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  • Best Books for Learning to Test Software

    - by Chris
    I have read a lot of programming books, many mention testing of various kinds. I have never really gotten into the topic of testing, but I realize how extremely important it is. Anyone know of some good books that provide a thorough exploration of this topic?

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  • self-destructing objects in php5?

    - by user151841
    I am working on a class in php that is basically an interface to a database row. I wanted to create a delete() method that would 1. delete the database row and 2. destroy the instance of itself so that further attempts to manipulate the row via the object would throw warnings. Doing some googling, it seems that, in php5, it's not possible for an object to unset itself. http://bugs.php.net/bug.php?id=36971 In fact they discuss the very situation I was wanting to do :( So how should I proceed? I could make boolean flag as a class property, for whether the row still exists, and have each operation check that flag and throw an error if the row has been deleted. This maintains the oo structure of code, so I would have $objDbRow->delete(); But then I have to put checks at the beginning of each method. Or, I could implement a __destruct method that deletes the row. But that would seem counter-intuitive to me; if I saw in code unset($objDbRow); All I would suspect that's happening is that the object is being discarded, not that a row is being deleted. So that to me would seem like bad practice.

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  • Should I be using libraries if I'm trying to learn how to program?

    - by CodeJustin.com
    I have been programming "a lot" in the past few months and at first I was trying to find the "easyest" language. Fortunately I realized that it's not about the language, it's about learning HOW to code. I ran into the Stanford lectures online (programming methodology) and I watched them all (around 23 hours total) awhile ago. Then I got into Java ME and programmed about 28.47% of a mobile RPG game (only around 2k lines of code). I feel like I learned a lot from those two experiences compared to previous ones but now that I'm moving into flash/actionscript 3.0 development and I'm finding myself learning like I did when I first started with PHP. I'm not really getting whats under the hood kind of. I'm finding myself using libraries to speed up development time which doesn't seem like a bad thing BUT I personally do not know how to write the libraries myself off hand. So should I be coding everything myself or is it ok to use libraries when you don't even know how to code them?

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