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• Random Loss of precision in Python ReadLine()

  - by jackyouldon

  Hi all, We have a process which takes a very large csv (1.6GB) and breaks it down into pieces (in this case 3). This runs nightly and normally doesn't give us any problems. When it ran last night, however, the first of the output files had lost precision on the numeric fields in the data. The active ingredient in the script are the lines: while lineCounter <= chunk: oOutFile.write(oInFile.readline()) lineCounter = lineCounter + 1 and the normal output might be something like StringField1; StringField2; StringField3; StringField4; 1000000; StringField5; 0.000054454 etc. On this one occasion and in this one output file the numeric fields were all output with 6 zeros at the end i.e. StringField1; StringField2; StringField3; StringField4; 1000000.000000; StringField5; 0.000000 We are using Python v2.6 (and don't want to upgrade unless we really have to) but we can't afford to lose this data. Does anyone have any idea why this might have happened? If the readline is doing some kind of implicit conversion is there a way to do a binary read, because we really just want this data to pass through untouched? It is very wierd to us that this only affected one of the output files generated by the same script, and when it was rerun the output was as expected. thanks Jack

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• easy c question: compare first char of a char array

  - by nunos

  How can I compare the first letter of the first element of a *char[]? I have done if (foo[0][0] == 'c') but that gives a segmentation fault

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• Checking for length of ul and removing an li element

  - by Legend

  I am trying to remove the last <li> element from a <ul> element only if it exceeds a particular length. For this, I am doing something like this: var selector = "#ulelement" if($(selector).children().length > threshold) { $(selector + " >:last").remove(); } I don't like the fact that I have to use the selector twice. Is there a shorter way to do this? Something like a "remove-if-length-greater-than-threshold" idea. I was thinking that maybe there is a way to do this using the live() function but I have no idea how.

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• Assigning Value to a variable that is too big for it! (checked and unchecked concept)

  - by ThickBook

  So when we assign a value to a variable then that variable should be able to hold it, right? and if not compiler produces the error. Now there is an option in C# known as Checked (which is by default) and unchecked option. But is there practical use of unchecked? any comments for a layman? :) Example: int a=int.MaxValue; int b=int.MaxValue; unchecked { int sum=a+b; }

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• (newbie) type signature "Maybe a" doesn't like "Just [Event]"

  - by sisif

  i'm still learning Haskell and need help with the type inference please! using packages SDL and Yampa i get the following type signature from FRP.Yampa.reactimate: (Bool -> IO (DTime, Maybe a)) and i want to use it for: myInput :: Bool -> IO (DTime, Maybe [SDL.Event]) myInput isBlocking = do event <- SDL.pollEvent return (1, Just [event]) ... reactimate myInit myInput myOutput mySF but it says Couldn't match expected type `()' against inferred type `[SDL.Event]' Expected type: IO (DTime, Maybe ()) Inferred type: IO (DTime, Maybe [SDL.Event]) In the second argument of `reactimate', namely `input' In the expression: reactimate initialize input output process i thought "Maybe a" allows me to use anything, even a SDL.Event list? why is it expecting "Maybe ()" when the type signature is actually "Maybe a"? why does it want an empty tuple, or a function taking no arguments, or what is () supposed to be?

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• What's a good starting point, tutorial, or project, to learn database programming?

  - by DarthNoodles

  I've been a Software Developer now for over 10 years. I've mostly worked in Embedded C with some time spent on C++ (limited) and Java. I'm looking to learn some new technologies and skills. I thought that database programming may be interesting to learn. I would like to make my own pet project in order to learn these things. My platform of choice is Windows but can work in Linux also. My ideal pet project would involve a GUI and some network/internet programming also which I have some experience doing. I wouldn't mind getting into C# but don't want to bite off more than I can chew right now as my spare time is limited. If I understand correctly SQLite allows for programs to use a database without running an ODBC server. Is this correct? Is that a good place to start? What can I do to start that is not too complicated but not so simple that I won't learn the details also? Your opinions and feedback would be appreciated.

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• new Integer vs valueOf

  - by LB

  Hi, I was using Sonar to make my code cleaner, and it pointed that I'm using new Integer(1) instead of Integer.valueOf(1). Because it seems that valueOf does not instantiate a new object so is more memory-friendly. How can valueOf not instantiate a new object ? How does it work ? Is this true for all integers ? thanks.

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• Differences between DB2 and Oracle

  - by Ondrej Slinták

  We had a talk with colleagues about databases yesterday as we will have a DB2 education in few weeks. I'm wondering, what are the differences between DB2 and Oracle as two major enterprise solutions? Are there any limitations in comparison to each other? Are there any tasks more suitable for DB2 or Oracle? (I found this article, but I somehow doubt it covers everything)

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• Error handling with Python + Pylons

  - by ensnare

  What is the proper way to handle errors with Python + Pylons? Say a user sets a password via a form that, when passed to a model class via the controller, throws an error because it's too short. How should that error be handled so that an error message gets displayed on the web page rather than the entire script terminating to an error page? Should there be any error handling in the controller itself? I hope I am explaining myself clearly. Thank you.

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• Normal C++ code in Qt doesnt build and run

  - by Nick

  Hello. I am using Qt under linux, if it matters. I ran successfully under Geany (a simple c++ compiler) the following: //my first program in C++ Hello World! include using namespace std; int main () {cout << "Hello World!"; return 0;} I opened Qt source file and copied the exact same code and i can't build or run. Thank you for your responses to this simple problem.

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• How to empty a list in Python?

  - by DrFalk3n

  It seems so "dirty" emptying a list in this way: while len(alist) > 0 : alist.pop() Does a clear way exist to do that?

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• Relationship problem?

  - by dilip

  I have four tables Tag=id,tag_name Image=Id,Image_name TagImage=Id,tag_id,Image_id ImageStudent=id,Image_id,student_id And I want to find a record using student id and tag name. What relationship do I use?

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• Processor, OS : 32bit, 64 bit

  - by Sandbox

  I am new to programming and come from a non-CS background (no formal degree). I mostly program winforms using C#. I am confused about 32 bit and 64 bit.... I mean, have heard about 32 bit OS, 32 bit processor and based on which a program can have maximum memory. How it affects the speed of a program. There are lot more questions which keep coming to mind. I tried to go through some Computer Organization and Architecture books. But, either I am too dumb to understand what is written in there or the writers assume that the reader has some CS background. Can someone explain me these things in a plain simple English or point me to something which does that. EDIT: I have read things like In 32-bit mode, they can access up to 4GB memory; in 64-bit mode, they can access much much more....I want to know WHY to all such things. BOUNTY: Answers below are really good....esp one by Martin. But, I am looking at a thorough explanation, but in plain simple English.

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• F# - Function with no arguments?

  - by Rubys

  When thinking in a functional mindset, given that functions are supposed to be pure, one can conclude any function with no arguments is basically just a value. However, reallity gets in the way, and with different inputs, I might not need a certain function, and if that function is computationally expensive, I'd like to not evaluate it if it's not needed. I found a workaround, using let func _ = ... and calling it with func 1 or whatever, but that feels very non-idiomatic and confusing to the reader. This boils down to one question: In F#, Is there a proper way to declare a function with zero arguments, without having it evaluated on declaration?

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• Getter/Setter Problem in Java?

  - by Praveen Chandrasekaran

  Hi Folks, I want to pass the String value between the classes both are same package. so i created the the classs like the code: public class Map_Delegate { String myLatitude; String myLongitude; String myName; private String TAG = "Map_Delegate"; public String getMyName() { return this.myName; } public void setMyName(String value) { Log.v(TAG, value); this.myName = value; } public String getMyLatitude() { return this.myLatitude; } public void setMyLatitude(String value) { Log.v(TAG, value); this.myLatitude = value; } public String getMyLongitude() { return this.myLongitude; } public void setMyLongitude(String value) { Log.v(TAG, value); this.myLongitude = value; } } But it can't pass the value. I done like this code to set the value: Map_Delegate map = new Map_Delegate(); map.setMyName(first_name_temp + " " + last_name_temp); map.setMyLatitude(homeLatitude_temp); map.setMyLongitude(homeLongitude_temp); code to get the value: Map_Delegate map = new Map_Delegate(); name_val = getMyName(); lat_val = getMyLatitude(); long_val = getMyLongitude(); Why get the Null value can you Guess? All classes in the same package and public .AnyIdea?

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• Python Class Variables Question

  - by zyq524

  I have some doubt about python's class variables. As my understanding, if I define a class variable, which is declared outside the init() function, this variable will create only once as a static variable in C++. This seems right for some python types, for instance, dict and list type, but for those base type, e.g. int,float, is not the same. For example: class A: dict1={} list1=list() int1=3 def add_stuff(self, k, v): self.dict1[k]=v self.list1.append(k) self.int1=k def print_stuff(self): print self.dict1,self.list1,self.int1 a1 = A() a1.add_stuff(1, 2) a1.print_stuff() a2=A() a2.print_stuff() The output is: {1: 2} [1] 1 {1: 2} [1] 3 I understand the results of dict1 and list1, but why does int1 behavior different?

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• Long variable names

  - by RaouL

  Lets say i have a variable that contains the number of search engine names in a file, what would you name it? number_of_seach_engine_names search_engine_name_count num_search_engines engines engine_names other name? The first name describes what the variable contains precisely, but isn't it too long?, any advice for choosing variable names? especially how to shorten a name that is too long or what kind of abbreviations to use?

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• Simple check authentication decorator in Python + Pylons

  - by ensnare

  I'd like to write a simple decorator that I can put above functions in my controller to check authentication and re-direct to the login page if the current user is not authenticated. What is the best way to do this? Where should the decorator go? How should I pass cookie info to the decorator? Sample code is greatly appreciated. Thank you!

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• how to write hello world in assembler under windows?

  - by feiroox

  Hi I wanted to write something basic in assembly under windows, I'm using nasm, but I can't get anything working. How to write and compile hello world without help of c functions on windows? thx

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• PHP Forms checkbox calculation

  - by Sef

  Hello, I am trying to perform some calculations with a form but every time i try to work with checkboxes it goes wrong. The checkboxes are beign set on value 1 in the form itselff and are being checked if there checked or not. $verdieping = isset($_POST["verdieping"]) ? $_POST["verdieping"] : 0; $telefoon = isset($_POST["telefoon"]) ? $_POST["telefoon"] : 0; $netwerk = isset($_POST["netwerk"]) ? $_POST["netwerk"] : 0; When i try to do calculations every works expect for the options with the checkboxes. When both checkboxes (telefoon & netwerk) are selected the value should be 30. If only one is selected the value should be 20. But no mather what i have tried to write down it always give problem, and it always uses 20, never the value 30. How do i solve this problem? Or suppose i am writing the syntax all wrong to lay conditions to a calculation? Any input appreciated. $standnaam = $_SESSION["standnaam"]; $oppervlakte = $_SESSION["oppervlakte"]; $verdieping = $_SESSION["verdieping"]; $telefoon = $_SESSION["telefoon"]; $netwerk = $_SESSION["netwerk"]; if ($oppervlakte <= 10) $tarief = 100; if ($oppervlakte > 10 && $oppervlakte <= 20) $tarief = 90; if ($oppervlakte > 20) $tarief = 80; if($verdieping == 1) { $prijsVerdieping = $oppervlakte * 120; } else { $prijsVerdieping = 0; } if(($telefoon == 1) && ($netwerk == 1)) { $prijsCom = 30; // never get this value, it always uses 20 } if(($telefoon == 1) || ($netwerk == 1)) { $prijsCom = 20; } $prijsOpp = $tarief * $oppervlakte; // works $totalePrijs = $prijsOpp + $prijsVerdieping + $prijsCom; //prijsCom value is always wrong Regards.

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• If you could remove one feature of php ti help newbies what would it be?

  - by Chris

  If you could remove one feature from PHP so as to discourage, prevent or otherwise help stop newer programmers develop bad habits or practices, or, to stop them falling into traps that might hinder their development skills what would it be and why? Now, before the votes to close it's not as open-ended as you might think. I'm not asking purely what is the worst feature or what feature would you really like to remove purely arbitrarily. Yes, there may not be one correct answer but I suspect there will be many similar answers which will provide me with a good idea of things I might be doing wrong, even inadvertently.

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• C++ STL: Trouble with string iterators

  - by Rosarch

  I'm making a simple command line Hangman game. void Hangman::printStatus() { cout << "Lives remaining: " << livesRemaining << endl; cout << getFormattedAnswer() << endl; } string Hangman::getFormattedAnswer() { return getFormattedAnswerFrom(correctAnswer.begin(), correctAnswer.end()); } string Hangman::getFormattedAnswerFrom(string::const_iterator begin, string::const_iterator end) { return begin == end? "" : displayChar(*begin) + getFormattedAnswerFrom(++begin, end); } char Hangman::displayChar(const char c) { return c; } (Eventually, I'll change this so displayChar() displays a - or a character if the user has guessed it, but for simplicity now I'm just returning everything.) When I build and run this from VS 2010, I get a popup box: Debug Assertion Failed! xstring Line: 78 Expression: string iterator not dereferenceable What am I doing wrong?

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• C and C++: Array element access pointer vs int

  - by begun

  Is there a performance difference if you either do myarray[ i ] or store the adress of myarray[ i ] in a pointer?

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• Python, lambda, find minimum

  - by qba

  I have foreach function which calls specified function on every element which it contains. I want to get minimum from thise elements but I have no idea how to write lambda or function or even a class that would manage that. Thanks for every help. I use my foreach function like this: o.foreach( lambda i: i.call() ) or o.foreach( I.call ) I don't like to make a lists or other objects. I want to iterate trough it and find min. I manage to write a class that do the think but there should be some better solution than that: class Min: def __init__(self,i): self.i = i def get_min(self): return self.i def set_val(self,o): if o.val < self.i: self.i = o.val m = Min( xmin ) self.foreach( m.set_val ) xmin = m.get_min() Ok, so I suppose that my .foreach method is non-python idea. I should do my Class iterable because all your solutions are based on lists and then everything will become easier. In C# there would be no problem with lambda function like that, so I though that python is also that powerful.

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• Codeigniter: how to track activity w/o using multiple db rows?

  - by Kevin Brown

  I need to track the completion of tasks for users. I started by having a row called "first_login", "profile_complete", "other_thing_complete", etc... I'd like to combine these all into one row "activity_state". I just don't know how to properly store data in this field, and how to retrieve it. What kind of field should it be, and how should I read/write to it?

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