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  • [Python] name 'OptionGroup' is not defined

    - by Cawas
    Ok, so I made this rookie mistake below, but in my defense I was led to it thanks to how the help about this subject is on python docs, which states how to use optparse. It is actually an error under the gigantic tutorial section. In contrast and to my offense, I may be one of the very few stupid people who can't read very well and pay close attention on what I do. But since this took me so long to discover, I wanted to "document" it here: Python 2.6.1 (r261:67515, Feb 11 2010, 00:51:29) >>> from optparse import OptionParser >>> outputGroup = OptionGroup(parser, 'Output handling') Traceback (most recent call last): File "<stdin>", line 1, in <module> NameError: name 'OptionGroup' is not defined This is strictly done with examples found on the docs, and you can't find anything about it anywhere, be it that long long docs page, google or stackoverflow. Plus, reading optparse.py shows OptionGroup is there, so that adds to the confusion. I bet it will take less than 1 minute for someone to spot my error. For that I'll only add proper tags and / or modify the title later on. :)

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  • Can the Singleton be replaced by Factory?

    - by lostiniceland
    Hello Everyone There are already quite some posts about the Singleton-Pattern around, but I would like to start another one on this topic since I would like to know if the Factory-Pattern would be the right approach to remove this "anti-pattern". In the past I used the singleton quite a lot, also did my fellow collegues since it is so easy to use. For example, the Eclipse IDE or better its workbench-model makes heavy usage of singletons as well. It was due to some posts about E4 (the next big Eclipse version) that made me start to rethink the singleton. The bottom line was that due to this singletons the dependecies in Eclipse 3.x are tightly coupled. Lets assume I want to get rid of all singletons completely and instead use factories. My thoughts were as follows: hide complexity less coupling I have control over how many instances are created (just store the reference I a private field of the factory) mock the factory for testing (with Dependency Injection) when it is behind an interface In some cases the factories can make more than one singleton obsolete (depending on business logic/component composition) Does this make sense? If not, please give good reasons for why you think so. An alternative solution is also appreciated. Thanks Marc

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  • Eclipse CDT setup for remote build

    - by Posco Grubb
    Is there a better way to setup Eclipse CDT for local editing and remote building? I am working on a C++ project that uses GNU make in Linux. The code is under CVS on a Linux server. When I'm in the lab, I use Eclipse CDT on a Linux-x64 PC. The project is built on a Linux-x86 PC. All the computers in the lab (including the CVS server) have NFS mounts. When I'm at home, I use Eclipse CDT on a Windows 7 PC. The Windows PC connects to the Linux CVS server via SSH tunnel. To edit source, I rsync the C++ project under the Linux Eclipse workspace back to my Windows Eclipse workspace. (I can also do a remote CVS checkout on the Windows PC.) To build from home, I use a custom build command that SSH's to the Linux-x86 PC, rsync's the C++ project from my Windows Eclipse workspace to my Linux Eclipse workspace, and then runs make on the Liunx-x86 PC, specifying the correct path for the Makefile. In order to go back and forth between lab and home without committing my changes to CVS every time, I use rsync. When I transition from lab to home, I rsync sources to my Windows Eclipse workspace. When I build from home, the sources get rsync'd back to the Linux Eclipse workspace. Is there a better, less wonky way to do this? (I'm NOT interested in remote debugging.)

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  • How do I create a good evaluation function for a new board game?

    - by A. Rex
    I write programs to play board game variants sometimes. The basic strategy is standard alpha-beta pruning or similar searches, sometimes augmented by the usual approaches to endgames or openings. I've mostly played around with chess variants, so when it comes time to pick my evaluation function, I use a basic chess evaluation function. However, now I am writing a program to play a completely new board game. How do I choose a good or even decent evaluation function? The main challenges are that the same pieces are always on the board, so a usual material function won't change based on position, and the game has been played less than a thousand times or so, so humans don't necessarily play it enough well yet to give insight. (PS. I considered a MoGo approach, but random games aren't likely to terminate.) Any ideas? Game details: The game is played on a 10-by-10 board with a fixed six pieces per side. The pieces have certain movement rules, and interact in certain ways, but no piece is ever captured. The goal of the game is to have enough of your pieces in certain special squares on the board. The goal of the computer program is to provide a player which is competitive with or better than current human players.

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  • IO operation taking long time for files in remote server

    - by user841311
    I have files of size 150 MB each in a remote server in a different domain in the network. I am accessing them thorugh UNC path. I want to read the file content and perform a basic string search. When I try reading the files line by line, the operation just don't finish and takes long time, more than 30 minutes. However when I copy those files to my local machine, the same code reads and performs the string search in less than 5 seconds. I don't have .NET framework installed in the server so I have to do this from my machine. I want to perform all this through C# code in .NET framework 3.5 so I don't want to explictly ftp all the files to my machine before performing this operation. Sample Code DirectoryInfo dir = new DirectoryInfo(@strFilePath); FileInfo[] fiArray = dir.getFiles("*.txt"); foreach (FileInfo fi in fiArray) { //reading file content from server takes long time but fast in local machine //perform string search } Let me know if my requirement is not clear. Thanks in advance!

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  • Spaced repetition (SRS) for learning

    - by Fredrik Johansson
    A client has asked me to add a simple spaced repeition algorithm (SRS) for an onlinebased learning site. But before throwing my self into it, I'd like to discuss it with the community. Basically the site asks the user a bunch of questions (by automatically selecting say 10 out of 100 total questions from a database), and the user gives either a correct or incorrect answer. The users result are then stored in a database, for instance: userid questionid correctlyanswered dateanswered 1 123 0 (no) 2010-01-01 10:00 1 124 1 (yes) 2010-01-01 11:00 1 125 1 (yes) 2010-01-01 12:00 Now, to maximize a users ability to learn all answers, I should be able to apply an SRS algorithm so that a user, next time he takes the quiz, receives questions incorrectly answered more often; than questions answered correctly. Also, questions that are previously answered incorrectly, but recently often answered correctly should occur less often. Have anyone implemented something like this before? Any tips or suggestions? Theese are the best links I've found: http://en.wikipedia.org/wiki/Spaced_repetition http://www.mnemosyne-proj.org/principles.php http://www.supermemo.com/english/ol/sm2.htm

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  • Properties vs. Fields: Need help grasping the uses of Properties over Fields.

    - by pghtech
    First off, I have read through a list of postings on this topic and I don't feel I have grasped properties because of what I had come to understand about encapsulation and field modifiers (private, public..ect). One of the main aspects of C# that I have come to learn is the importance of data protection within your code by the use of encapsulation. I 'thought' I understood that to be because of the ability of the use of the modifiers (private, public, internal, protected). However, after learning about properties I am sort of torn in understanding not only properties uses, but the overall importance/ability of data protection (what I understood as encapsulation) within C#. To be more specific, everything I have read when I got to properties in C# is that you should try to use them in place of fields when you can because of: 1) they allow you to change the data type when you can't when directly accessing the field directly. 2) they add a level of protection to data access However, from what I 'thought' I had come to know about the use of field modifiers did #2, it seemed to me that properties just generated additional code unless you had some reason to change the type (#1) - because you are (more or less) creating hidden methods to access fields as opposed to directly. Then there is the whole modifiers being able to be added to Properties which further complicates my understanding for the need of properties to access data. I have read a number of chapters from different writers on "properties" and none have really explained a good understanding of properties vs. fields vs. encapsulation (and good programming methods). Can someone explain: 1) why I would want to use properties instead of fields (especially when it appears I am just adding additional code 2) any tips on recognizing the use of properties and not seeing them as simply methods (with the exception of the get;set being apparent) when tracing other peoples code? 3) Any general rules of thumb when it comes to good programming methods in relation to when to use what? Thanks and sorry for the long post - I didn't want to just ask a question that has been asked 100x without explaining why I am asking it again.

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  • sql query - how to apply limit within group by

    - by Raj
    hey guys assuming i have a table named t1 with following fields: ROWID, CID, PID, Score, SortKey it has the following data: 1, C1, P1, 10, 1 2, C1, P2, 20, 2 3, C1, P3, 30, 3 4, C2, P4, 20, 3 5, C2, P5, 30, 2 6, C3, P6, 10, 1 7, C3, P7, 20, 2 what query do i write so that it applies group by on CID, but instead of returning me 1 single result per group, it returns me a max of 2 results per group. also where condition is score = 20 and i want the results ordered by CID and SortKey. If I had to run my query on above data, i would expect the following result: RESULTS FOR C1 - note: ROWID 1 is not considered as its score < 20 C1, P2, 20, 2 C1, P3, 30, 3 RESULTS FOR C2 - note: ROWID 5 appears before ROWID 4 as ROWID 5 has lesser value SortKey C2, P5, 30, 2 C2, P4, 20, 3 RESULTS FOR C3 - note: ROWID 6 does not appear as its score is less than 20 so only 1 record returned here C3, P7, 20, 2 IN SHORT, I WANT A LIMIT WITHIN A GROUP BY. I want the simplest solution and want to avoid temp tables. sub queries are fine. also note i am using sqlite for this

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  • Shape object in Processing, translate individual shapes.

    - by Zain
    I am relatively new to Processing but have been working in Java for about 2 years now. I am facing difficulty though with the translate() function for objects as well as objects in general in processing. I went through the examples and tried to replicate the manners by which they instantiated the objects but cannot seem to even get the shapes to appear on the screen no less move them. I instantiate the objects into an array using a nested for loop and expect a grid of the objects to be rendered. However, nothing at all is rendered. My nested for loop structure to instantiate the tiles: for(int i=0; i<102; i++){ for(int j=0; j<102; j++){ tiles[i][j]=new tile(i,0,j); tiles[i][j].display(); } } And the constructors for the tile class: tile(int x, int y, int z){ this.x=x; this.y=y; this.z=z; beginShape(); vertex(x,y,z); vertex(x+1,y,z); vertex(x+1,y,z-1); vertex(x,y,z-1); endShape(); } Nothing is rendered at all when this runs. Furthermore, if this is of any concern, my translations(movements) are done in a method I wrote for the tile class called move which simply calls translate. Is this the correct way? How should one approach this? I can't seem to understand at all how to render/create/translate individual objects/shapes. Thanks for any help any of you are able to provide!

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  • Fast, very lightweight algorithm for camera motion detection?

    - by Ertebolle
    I'm working on an augmented reality app for iPhone that involves a very processor-intensive object recognition algorithm (pushing the CPU at 100% it can get through maybe 5 frames per second), and in an effort to both save battery power and make the whole thing less "jittery" I'm trying to come up with a way to only run that object recognizer when the user is actually moving the camera around. My first thought was to simply use the iPhone's accelerometers / gyroscope, but in testing I found that very often people would move the iPhone at a consistent enough attitude and velocity that there wouldn't be any way to tell that it was still in motion. So that left the option of analyzing the actual video feed and detecting movement in that. I got OpenCV working and tried running their pyramidal Lucas-Kanade optical flow algorithm, which works well but seems to be almost as processor-intensive as my object recognizer - I can get it to an acceptable framerate if I lower the depth levels / downsample the image / track fewer points, but then accuracy suffers and it starts to miss some large movements and trigger on small hand-shaking-y ones. So my question is, is there another optical flow algorithm that's faster than Lucas-Kanade if I just want to detect the overall magnitude of camera movement? I don't need to track individual objects, I don't even need to know which direction the camera is moving, all I really need is a way to feed something two frames of video and have it tell me how far apart they are.

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  • Trouble with __VA_ARGS__

    - by Noah Roberts
    C++ preprocessor __VA_ARGS__ number of arguments The accepted answer there doesn't work for me. I've tried with MSVC++ 10 and g++ 3.4.5. I also crunched the example down into something smaller and started trying to get some information printed out to me in the error: template < typename T > struct print; #include <boost/mpl/vector_c.hpp> #define RSEQ_N 10,9,8,7,6,5,4,3,2,1,0 #define ARG_N(_1,_2,_3,_4,_5,_6,_7,_8,_9,_10,N,...) N #define ARG_N_(...) ARG_N(__VA_ARGS__) #define XXX 5,RSEQ_N #include <iostream> int main() { print< boost::mpl::vector_c<int, ARG_N_( XXX ) > > g; // ARG_N doesn't work either. } It appears to me that the argument for ARG_N ends up being 'XXX' instead of 5,RSEQ_N and much less 5,10,...,0. The error output of g++ more specifically says that only one argument is supplied. Having trouble believing that the answer would be proposed and then accepted when it totally fails to work, so what am I doing wrong? Why is XXX being interpreted as the argument and not being expanded? In my own messing around everything works fine until I try to pass off VA_ARGS to a macro containing some names followed by ... like so: #define WTF(X,Y,...) X , Y , __VA_ARGS__ #define WOT(...) WTF(__VA_ARGS__) WOT(52,2,5,2,2) I've tried both with and without () in the various macros that take no input.

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  • With Go, how to append unknown number of byte into a vector and get a slice of bytes?

    - by Stephen Hsu
    I'm trying to encode a large number to a list of bytes(uint8 in Go). The number of bytes is unknown, so I'd like to use vector. But Go doesn't provide vector of byte, what can I do? And is it possible to get a slice of such a byte vector? I intends to implement data compression. Instead of store small and large number with the same number of bytes, I'm implements a variable bytes that uses less bytes with small number and more bytes with large number. My code can not compile, invalid type assertion: 1 package main 2 3 import ( 4 //"fmt" 5 "container/vector" 6 ) 7 8 func vbEncodeNumber(n uint) []byte{ 9 bytes := new(vector.Vector) 10 for { 11 bytes.Push(n % 128) 12 if n < 128 { 13 break 14 } 15 n /= 128 16 } 17 bytes.Set(bytes.Len()-1, bytes.Last().(byte)+byte(128)) 18 return bytes.Data().([]byte) // <- 19 } 20 21 func main() { vbEncodeNumber(10000) } I wish to writes a lot of such code into binary file, so I wish the func can return byte array. I haven't find a code example on vector.

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  • 1k of Program Space, 64 bytes of RAM. Is assembly an absolute must?

    - by Earlz
    (If your lazy see bottom for TL;DR) Hello, I am planning to build a new (prototype) project dealing with physical computing. Basically, I have wires. These wires all need to have their voltage read at the same time. More than a few hundred microseconds difference between the readings of each wire will completely screw it up. The Arduino takes about 114 microseconds. So the most I could read is 2 or 3 wires before the latency would skew the accuracy of the readings. So my plan is to have an Arduino as the "master" of an array of ATTinys. The arduino is pretty cramped for space, but it's a massive playground compared to the tinys. An ATTiny13A has 1k of flash ROM(program space), 64 bytes of RAM, and 64 bytes of (not-durable and slow) EEPROM. (I'm choosing this for price as well as size) The ATTinys in my system will not do much. Basically, all they will do is wait for a signal from the Master, and then read the voltage of 1 or 2 wires and store it in RAM(or possibly EEPROM if it's that cramped). And then send it to the Master using only 1 wire for data.(no room for more than that!). So far then, all I should have to do is implement trivial voltage reading code (using built in ADC). But this communication bit I'm worried about. Do you think a communication protocol(using just 1 wire!) could even be implemented in such constraints? TL;DR: In less than 1k of program space and 64 bytes of RAM(and 64 bytes of EEPROM) do you think it is possible to implement a 1 wire communication protocol? Would I need to drop to assembly to make it fit? I know that currently my Arduino programs linking to the Wiring library are over 8k, so I'm a bit concerned.

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  • Strategy for WCF server with .Net clients and Android clients?

    - by D.H.
    I am using WCF to write a server that should be able to communicate with .Net clients, Android clients and possibly other types of clients. The main type of client is a desktop application that will be written in .Net. This client will usually be on the same intranet as the server. It will make an initial call to the server to get the current state of the system and will then receive updates from the server whenever a value changes. These updates are frequent, perhaps once a second. The Android clients will connect over the Internet. This client is also interested in updates, but it is not as critical as for the desktop client so a (less frequent) polling scenario might be acceptable. All clients will have to login to use the services, and when connecting over the Internet the connection should be secure. I am familiar with WCF but I am not sure what bindings are most appropriate for the scenario and what security solution to use. Also, I have not used Android, but I would like to make it as simple as possible for the person implementing the Android client to consume my services. So, what is my strategy?

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  • Excel::Shape object getting released automatically after the count reaches 18 in List<T>

    - by A9S6
    I have a Excel addin written in C# 2.0 in which I am experiencing a strange behavior.Please note that this behavior is only seen in Excel 2003 and NOT in Excel 2007 or 2010. Issue: When the user clicks an import command button, a file is read and a number of Shapes are created/added to the worksheet using Worksheet::Shapes::AddPicture() method. A reference to these Shape objects are kept in a generic list: List<Excel.Shape> list = new List<Excel.Shape>(); Everything works fine till the list has less than 18 references. When the count reaches 18, and a new Shape reference is added, the first one i.e. @ index [0] is released. I am unable to call any method or property on that reference and calling a method/property throws a COMException (0x800A1A8) i.e. Object Required. If I add one more, then the reference @ [1] is not accessible and so on. Strange enough... this happens with Shape object only i.e. If I add one Shape and then 17 nulls to the list then this wont happen until 17 more Shape objects are added. Does anyone has an idea why it happens after the count reaches 18? I thought it might be something with the List's default capacity. Something like relocating the references during which they get released so I initialized it with a capacity of 1000 but still no luck. List<Excel.Shape> list = new List<Excel.Shape>(1000); Any Idea??

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  • Apple's Sample App TopSongs has 26 Leaks, Ugh!

    - by RoLYroLLs
    Hey all, I've been building an app for a client and part of it uses Apple's TopSongs sample app to download data on another thread. I finally got enough done to start testing that part and found 1000 leaks!!! A closer look at the leaks made me check TopSongs for leaks, since none of the my methods were in leaks report. Running TopSongs returned 26 leaks. Not quite sure how to fix them, or if they are part of some library from Apple. I bet you're asking if it has 26, why do you have 1000? Well, I use their sample to make roughly 48 calls to webservices to get all the information needed on initial install (48 calls x 26 leaks = 1248 leaks!!). Later it makes at least 12 calls + 4 to check for updated information on other sections of the app. Can't do a thing about it, can't make one call, or less calls, please don't comment about this part. I seen people respond to posts that aren't necessarily answering the question the user originally posted, which in this case is has anyone tried patching up the leaks, if they are patchable, or is this a bug in Apple's libraries? Thanks so much.

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  • How to choose light version of databse system

    - by adopilot
    I am starting one POS (Point of sale) project. Targeting system is going to be written in C# .NET 2 WinForms and as main database server We are going to use MS-SQL Server. As we have a lot of POS devices in chain for one store I will love to have backend local data base system on each POS device. Scenario are following: When main server goes down!! POS application should continue working "off-line" with local database, until connection to main server come up again. Now I am in dilemma which local database is going to be most adoptable for me. Here is some notes for helping me point me in right direction: To be Light "My POS devices art usually old and suffering with performances" To be Free "I have a lot of devices and I do not wont additional cost beside main SQL serer" One day Ill love to try all that port on Mono and Linux OS. Here is what I've researched so far: Simple XML "Light but I am afraid of performance, My main table of items is average of 10K records" SQL-Expres "I am afraid that my POS devices is poor with hardware for SQLExpres, and also hard to install on each device and configure" Less known Advantage Database Server have free distribution of offline ADT system. DBF with extended Library,"Respect for good old DBFs but that era is behind Me with clipper and DBFs" MS Access Sqlite "Mostly like for now, but I am afraid how it is going to pair with MS SQL do they have same Data taypes". I know that in this SO is a lot of subjective data, but at least can someone recommended some others lite database system, or things that I shod most take attention before I choice database.

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  • Can I automatically throw descriptive exceptions with parameter values and class feild information?

    - by Robert H.
    I honestly don't throw exceptions often. I catch them even less, ironically. I currently work in shop where we let them bubble up to avicode. For whatever reason, however, avicode isn't configured to capture some of the critical bits I need when these exceptions come bouncing back to my attention. Specifically, I'd like to see the parameter values and the class’s field data at the time of the exception. I’d guess with the large suite of .Net services that I could create a static method to crawl up the stack, gather these bits and store them in a string that I could stick in my exception message. I really don't are how long such a method would take to execute as performance is no longer a concern when I hit one of these scenarios. If it's possible, I'm sure someone has done it. If that's the case, I'm having a hard time finding it. I think any search containing "exception" brings back too many resutls. Anyway, can this be done? If so, some examples or links would be great. Thanks in advance for your time, Robert

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  • Runtime Exception when using Custom Healthmonitoring event in medium trust

    - by Elementenfresser
    Hi, I'm using custom healthmonitoring events in ASP.NET We recently moved to a new server with default High Trust Permissions. Literature says that healthmonitoring and custom events should work under Medium or higher trust (http://msdn.microsoft.com/en-us/library/bb398933.aspx). Problem is it doesn't. In less than high trust I get a SecurityException saying The application attempted to perform an operation not allowed by the security policy It works in Full trust or when I remove the inheritance of System.Web.Management.WebErrorEvent. Any suggestions anyone? Here is the super simple code behind with a custom event defined: public partial class Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { try { CallCustomEvent(); } catch (Exception ex) { Response.Write(ex.Message); throw ex; } } /// <summary> /// this metho is never called due to lacking permissions... /// </summary> private void CallCustomEvent() { try { //do something useful here } catch (Exception) { //code to instantiate the forbidden inheritance... WebBaseEvent.Raise(new CustomEvent()); } } } /// <summary> /// custom error inheriting WebErrorEvent which is not allowed in high trust? can't believe that... /// </summary> public class CustomEvent : WebErrorEvent { public CustomEvent() : base("test", HttpContext.Current.Request, 100001, new ApplicationException("dummy")) { } } and the Web Config excerpt for high trust: <system.web> <trust level="High" originUrl="" />

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  • Custom Calculations in a Matrix - Reporting Services 2005

    - by bfrancis
    I am writing a report to show gas usage (in gallons) used by each department. The request is to view each month and the gallons used by each department. A column is required to display what each departments target goal is, based on the gallons of gas they have used in a past time frame. Each departments target goal is x percent less than the total gallons used for said time frame. I currently have a matrix in Reporting Services with departments making up rows, months making up columns, and gallons filling the details. The matrix is being filled by dataset1. I have the data grouping as is requested for each month by each department. My problem is calculating the target goal. My thought was to create a second dataset (dataset2) that returns the gallons used based on the time frame requested. I grouped this data by department. I was hoping I could use the department field in each dataset to make sure the appropriate numbers were used. I added a new column which shows up next to the gallons field. As I attempted to build the Expression I found out that I could only grab the gallons used from dataset2 if I was summing the gallons field. This gives me the total gallons used by every department combined. I have tried to find resources with similar examples of what I am trying to accomplish but I cannot seem to come across one. I am trying to keep this as detailed as possible without making it too wordy. I would be more than happy to clarify or explain into further detail what I have written above if it is needed. If anyone has links, comments, or suggestions they would be greatly appreciated. A very simple visual or what I am hoping to accomplish is below. The months and departments would expand based on the data returned. months ------------------------------ departments| gallons/month | target goal

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  • How do I left join tables in unidirectional many-to-one in Hibernate?

    - by jbarz
    I'm piggy-backing off of http://stackoverflow.com/questions/2368195/how-to-join-tables-in-unidirectional-many-to-one-condition. If you have two classes: class A { @Id public Long id; } class B { @Id public Long id; @ManyToOne @JoinColumn(name = "parent_id", referencedColumnName = "id") public A parent; } B - A is a many to one relationship. I understand that I could add a Collection of Bs to A however I do not want that association. So my actual question is, Is there an HQL or Criteria way of creating the SQL query: select * from A left join B on (b.parent_id = a.id) This will retrieve all A records with a Cartesian product of each B record that references A and will include A records that have no B referencing them. If you use: from A a, B b where b.a = a then it is an inner join and you do not receive the A records that do not have a B referencing them. I have not found a good way of doing this without two queries so anything less than that would be great. Thanks.

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  • How can I change some specific carps into croaks in Perl?

    - by sid_com
    I tried to catch a carp-warning: carp "$start is > $end" if (warnings::enabled()); ) with eval {} but it didn't work, so I looked in the eval documentation and I discovered, that eval catches only syntax-errors, run-time-errors or executed die-statements. How could I catch a carp warning? #!/usr/bin/env perl use warnings; use strict; use 5.012; use List::Util qw(max min); use Number::Range; my @array; my $max = 20; print "Input (max $max): "; my $in = <>; $in =~ s/\s+//g; $in =~ s/(?<=\d)-/../g; eval { my $range = new Number::Range( $in ); @array = sort { $a <=> $b } $range->range; }; if ( $@ =~ /\d+ is > \d+/ ) { die $@ }; # catch the carp-warning doesn't work die "Input greater than $max not allowed $!" if defined $max and max( @array ) > $max; die "Input '0' or less not allowed $!" if min( @array ) < 1; say "@array";

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  • Listing serial (COM) ports on Windows?

    - by Eli Bendersky
    Hello, I'm looking for a robust way to list the available serial (COM) ports on a Windows machine. There's this post about using WMI, but I would like something less .NET specific - I want to get the list of ports in a Python or a C++ program, without .NET. I currently know of two other approaches: Reading the information in the HARDWARE\\DEVICEMAP\\SERIALCOMM registry key. This looks like a great option, but is it robust? I can't find a guarantee online or in MSDN that this registry cell indeed always holds the full list of available ports. Tryint to call CreateFile on COMN with N a number from 1 to something. This isn't good enough, because some COM ports aren't named COMN. For example, some virtual COM ports created are named CSNA0, CSNB0, and so on, so I wouldn't rely on this method. Any other methods/ideas/experience to share? Edit: by the way, here's a simple Python implementation of reading the port names from registry: import _winreg as winreg import itertools def enumerate_serial_ports(): """ Uses the Win32 registry to return a iterator of serial (COM) ports existing on this computer. """ path = 'HARDWARE\\DEVICEMAP\\SERIALCOMM' try: key = winreg.OpenKey(winreg.HKEY_LOCAL_MACHINE, path) except WindowsError: raise IterationError for i in itertools.count(): try: val = winreg.EnumValue(key, i) yield (str(val[1]), str(val[0])) except EnvironmentError: break

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  • Asynchronous event loop design and issues.

    - by Artyom
    Hello, I'm designing event loop for asynchronous socket IO using epoll/devpoll/kqueue/poll/select (including windows-select). I have two options of performing, IO operation: Non-blocking mode, poll on EAGAIN Set socket to non-blocking mode. Read/Write to socket. If operation succeeds, post completion notification to event loop. If I get EAGAIN, add socket to "select list" and poll socket. Polling mode: poll and then execute Add socket to select list and poll it. Wait for notification that it is readable writable read/write Post completion notification to event loop of sucseeds To me it looks like first would require less system calls when using in normal mode, especially for writing to socket (buffers are quite big). Also it looks like that it would be possible to reduce the overhead over number of "select" executions, especially it is nice when you do not have something that scales well as epoll/devpoll/kqueue. Questions: Are there any advantages of the second approach? Are there any portability issues with non-blocking operations on sockets/file descriptors over numerous operating systems: Linux, FreeBSD, Solaris, MacOSX, Windows. Notes: Please do not suggest using existing event-loop/socket-api implementations

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  • Using diff and patch to force one local code base to look like another

    - by Dave Aaron Smith
    I've noticed this strange behavior of diff and patch when I've used them to force one code base to be identical to another. Let's say I want to update update_me to look identical to leave_unchanged. I go to update_me. I run a diff from leave_unchanged to update_me. Then I patch the diff into update_me. If there are new files in leave_unchanged, patch asks me if my patch was reversed! If I answer yes, it deletes the new files in leave_unchanged. Then, if I simply re-run the patch, it correctly patches update_me. Why does patch try to modify both leave_unchanged and update_me? What's the proper way to do this? I found a hacky way which is to replace all +++ lines with nonsense paths so patch can't find leave_unchanged. Then it works fine. It's such an ugly solution though. $ mkdir copyfrom $ mkdir copyto $ echo "Hello world" > copyfrom/myFile.txt $ cd copyto $ diff -Naur . ../copyfrom > my.diff $ less my.diff diff -Naur ./myFile.txt ../copyfrom/myFile.txt --- ./myFile.txt 1969-12-31 19:00:00.000000000 -0500 +++ ../copyfrom/myFile.txt 2010-03-15 17:21:22.000000000 -0400 @@ -0,0 +1 @@ +Hello world $ patch -p0 < my.diff The next patch would create the file ../copyfrom/myFile.txt, which already exists! Assume -R? [n] yes patching file ../copyfrom/myFile.txt $ patch -p0 < my.diff patching file ./myFile.txt

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