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• Can FileOutputStream() take a relative path as an argument

  - by Ankur

  I am creating a FileOutputStream object. It takes a file or String as an argument in its constructor. My question is, can I give it a relative URL as an argument for the location of a file, it doesn't seem to work, but I am trying to work out if this is possible at all (if not I will stop trying). If it is not possible, how can I (from a servlet) get the absolute path (on the filesystem, not the logical URL) to the current location in such a way that I can pass that to the constructor. Part of my problem is that my dev box is Windows but I will publish this to a Unix box, so the paths cannot be the same i.e. on Windows C:/.... and on unix /usr/...

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• Sort CMap Key by String Length

  - by Yan Cheng CHEOK

  Previously, I am using STL map to perform the mentioned task. struct ltstr { bool operator()(std::string s1, std::string s2) const { const int l1 = s1.length(); const int l2 = s2.length(); if (l1 == l2) { // In alphabetical order. return s1.compare(s2) < 0; } // From longest length to shortest length. return l1 > l2; } }; std::map<std::string, int, ltstr> m; How can I perform the same task using CMap? // How to make key sorted by string length? CMap<CString, LPCTSTR, int, int> m;

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• Why is floating point byte swapping different from integer byte swapping?

  - by CJ

  I have a binary file of doubles that I need to load using C++. However, my problem is that it was written in big-endian format but the fstream operator will then read the number wrong because my machine is little-endian. It seems like a simple problem to resolve for integers, but for doubles and floats the solutions I have found won't work. How can I (or should I) fix this? I read this as a reference for integer byte swapping: http://stackoverflow.com/questions/105252/how-do-i-convert-between-big-endian-and-little-endian-values-in-c

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• What documents/requirements do you need from clients to develop web projects ?

  - by kacalapy

  I have an interview coming up where I would be a consultant to a small advertising agency. They crank out web sites for clients using DNN. tTe company owner/ operator asked me what I need in order to run with something and get it done, and eluded to wire frames and a site map. I am more used to having more detailed work and in a full time company environment but in these times it looks like we all need to be a bit more flexible. Typically I have functional and non-functional specifications defined for development work. This way I can control what is in scope, manage expectations, get sign offs, track deliverables and so on. Are there any contractors out there who develop web sites andcan advise me on the best approach to this so that I don't look foolish and get burned or taken advantage of? thanks

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• In SQL, we can use "Union" to merge two tables. What are different ways to do "Intersection"?

  - by Jian Lin

  In SQL, there is an operator to "Union" two tables. In an interview, I was told that, say one table has just 1 field with 1, 2, 7, 8 in it, and another table also has just 1 field with 2, and 7 in it, how do I get the intersection. I was stunned at first, because I never saw it that way. Later on, I found that it is actually a "Join" (inner join), which is just select * from t1, t2 where t1.number = t2.number (although the name "join" feels more like "union" rather than "intersect") another solution seems to be select * from t1 INTERSECT select * from t2 but it is not supported in MySQL. Are there different ways to get the intersection besides these two methods?

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• Allow for modular development while still running in same JVM?

  - by Marcus

  Our current app runs in a single JVM. We are now splitting up the app into separate logical services where each service runs in its own JVM. The split is being done to allow a single service to be modified and deployed without impacting the entire system. This reduces the need to QA the entire system - just need to QA the interaction with the service being changed. For inter service communication we use a combination of REST, an MQ system bus, and database views. What I don't like about this: REST means we have to marshal data to/from XML DB views couple the systems together which defeats the whole concept of separate services MQ / system bus is added complexity There is inevitably some code duplication between services You have set up n JBoss server configurations, we have to do n number of deployments, n number of set up scripts, etc, etc. Is there a better way to structure an internal application to allow modular development and deployment while allowing the app to run in a single JVM (and achieving the associated benefits)?

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• Boost::Container::Vector with Enum Template Argument - Not Legal Base Class

  - by CuppM

  Hi, I'm using Visual Studio 2008 with the Boost v1.42.0 library. If I use an enum as the template argument, I get a compile error when adding a value using push_back(). The compiler error is: 'T': is not a legal base class and the location of the error is move.hpp line 79. #include <boost/interprocess/containers/vector.hpp> class Test { public: enum Types { Unknown = 0, First = 1, Second = 2, Third = 3 }; typedef boost::container::vector<Types> TypesVector; }; int main() { Test::TypesVector o; o.push_back(Test::First); return 0; } If I use a std::vector instead it works. And if I resize the Boost version first and then set the values using the [] operator it also works. Is there some way to make this work using push_back()?

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• Tool to automatically add tracing or instrumentation to an .NET app?

  - by Tony_Henrich

  I have a .NET app which runs once a day. Sometimes there's a logical error somewhere which occurs randomly. Is there a tool like Eqatec's Tracer which automatically injects instrumentation in the code and logs everything to a file? The issue with Eqatec's Tracer is that it opens a window on the machine and it doesn't seem to log. My issue rarely occurs and I need to keep all logs for a long time. I don't want to change the source code and add logging statements all over the place. I am aware of PostSharp & Logfaces.

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• Is this call to a function object inlined?

  - by dehmann

  In the following code, Foo::add calls a function via a function object: struct Plus { inline int operator()(int x, int y) const { return x + y; } }; template<class Fct> struct Foo { Fct fct; Foo(Fct f) : fct(f) {} inline int add(int x, int y) { return fct(x,y); // same efficiency adding directly? } }; Is this the same efficiency as calling x+y directly in Foo::add? In other words, does the compiler typically directly replace fct(x,y) with the actual call, inlining the code, when compiling with optimizations enabled?

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• Declaring pointers; asterisk on the left or right of the space between the type and name?

  - by GenTiradentes

  I've seen mixed versions of this in a lot of code. (This applies to C and C++, by the way.) People seem to declare pointers in one of two ways, and I have no idea which one is correct, of if it even matters. The first way it to put the asterisk adjacent the type name, like so: someType* somePtr; The second way is to put the asterisk adjacent the name of the variable, like so: someType *somePtr; This has been driving me nuts for some time now. Is there any standard way of declaring pointers? Does it even matter how pointers are declared? I've used both declarations before, and I know that the compiler doesn't care which way it is. However, the fact that I've seen pointers declared in two different ways leads me to believe that there's a reason behind it. I'm curious if either method is more readable or logical in some way that I'm missing.

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• Good excuses NOT to use version control

  - by Kent Fredric

  This question may seem backwards to all logical reasoning, but I encountered a team member who was working on a side project out of the main tree, and had decided ( rephrased ) I'm the only developer, we don't need version control, that's stupid Now personally, the idea horrifies me, and I can't for one justify it. So now my stance is clear, I want some legitimate answers why somebody can excuse themselves from using version control. The default answers will of course be "there is no excuse". Not what I want to see. If you can't see an excuse, then just don't post. ( Feel free to downmod excuses others post that are illegitimate/bad and give reasoning )

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• Is there alternative way to write this query?

  - by Kugel

  I have tables A, B, C, where A represents items which can have zero or more sub-items stored in C. B table only has 2 foreign keys to connect A and C. I have this sql query: select * from A where not exists (select * from B natural join C where B.id = A.id and C.value > 10); Which says: "Give me every item from table A where all sub-items have value less than 10. Is there a way to optimize this? And is there a way to write this not using exists operator?

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• visual studio intellisense error

  - by rakkarage

  template <typename T> class Test { friend Test<T> & operator * (T lhs, const Test<T> & rhs) { Test<T> r(rhs); // return r *= lhs; } } 4 IntelliSense: identifier "T" is undefined why is T defined on line 3 but not line 4? i mean i guess its not a real error just an intellisense error... it works anyway but is there something wrong? can i fix it? or remove the red squiggles somehow? thanks i am using visual studio 2010... i wonder if this happens in other versions as well?

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• Having an @ inside of a string - PHP

  - by Msencenb

  So I know that you use a backslash to escape most things in php however the @ symbol is an operator that suppresses error messages. I'm trying to put an email string like this inside of an array "[email protected]", however php is throwing an error. How do you escape the @ sign? EDIT: Here is the code example that was throwing the error: $arr = array(3=> "[email protected]",4=> "[email protected]"); However replacing the double quotes with single quotes fixes the error as answered below.... why is that true?

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• Why does sh/bash set command line parameter values when trying to set environment variable?

  - by Touko

  A question on basics : While tuning environment variables for a program launched from a script, I ended up with somewhat strange behaviour with sh (which seems to be actually linked to bash) : variable setting seems to mess up with command-line parameters. Could somebody explain why does this happen? A simple script: #! /bin/sh # Messes with $1 ?? set ANT_OPTS=-Xmx512M export ANT_OPTS # Works # export ANT_OPTS=-Xmx512M echo "0 = $0" echo "1 = $1" When I run this with the upper alternative (set + export), the result is as following: $ ./test.sh foo 0 = ./test.sh 1 = ANT_OPTS=-Xmx512M But with lower alternative (export straight), the result is as I supposed: $ ./test.sh foo 0 = ./test.sh 1 = foo There is surely logical explanation, I just haven't figured it out yet. Somebody who does have idea? br, Touko

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• 'Lexical' scoping of type parameters in C#

  - by leppie

  I have 2 scenarios. This fails: class F<X> { public X X { get; set; } } error CS0102: The type 'F' already contains a definition for 'X' This works: class F<X> { class G { public X X { get; set; } } } The only logical explanation is that in the second snippet the type parameter X is out of scope, which is not true... Why should a type parameter affect my definitions in a type? IMO, for consistency, either both should work or neither should work. Any other ideas? PS: I call it 'lexical', but it probably is not not the correct term.

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• When does ref($variable) return 'IO'?

  - by Zaid

  Here's the relevant excerpt from the documentation of the ref function: The value returned depends on the type of thing the reference is a reference to. Builtin types include: SCALAR ARRAY HASH CODE REF GLOB LVALUE FORMAT IO VSTRING Regexp Based on this, I imagined that calling ref on a filehandle would return 'IO'. Surprisingly, it doesn't: use strict; use warnings; open my $fileHandle, '<', 'aValidFile'; close $fileHandle; print ref $fileHandle; # prints 'GLOB', not 'IO' perlref tries to explain why: It isn't possible to create a true reference to an IO handle (filehandle or dirhandle) using the backslash operator. The most you can get is a reference to a typeglob, which is actually a complete symbol table entry [...] However, you can still use type globs and globrefs as though they were IO handles. In what circumstances would ref return 'IO' then?

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• Problem of using cin twice.

  - by gc

  Here is the code: string str; cinstr; cout<<"first input:"<<str<<endl; getline(cin, str); cout<<"line input:"<<str<<endl; The result is that getline never pauses for user input, therefore the second output is always empty. After spending some time on it, I realized after the first call "cinstr", it seems '\n' is still stored in cin (using cin.peek() to check), which ends getline immediately. The solution will be adding one more line between the first usage and the second one: cin.ignore(numeric_limits::max(), '\n'); However, I still don't understand, why is '\n' left there after the first call? What does istream& operator really do?

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• C# : Number Conversion Problem

  - by Sayem Ahmed

  Today I faced a strange problem in C#. I have an ASP.NET page where user can enter certain price, quantity etc. I get the price value, convert it to double, then multiply it with 100 and then typecast it to an integer. When the price is "33.30", after converting it to double it remains 33.3 (obviously...), but after multiplying it with 100, it becomes 3329.9999999999995, and when I cast it to integer by applying simple cast operator "(int) (price * 100) ", it becomes 3329. Right now I have no idea why this is happening. So I thought may be you guys can help :) .

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• How does Hibernate detect dirty state of an entity object?

  - by ???'Lenik

  Is it using some kind of byte codes modification to the original classes? Or, maybe Hibernate get the dirty state by compare the given object with previously persisted version? I'm having a problem with hashCode() and equals() methods for complicated objects. I feel it would be very slow to compute hash code if the object has collection members, and cyclic references are also a problem. If Hibernate won't use hashCode()/equals() to check the dirty state, I guess I should not use equals()/hashCode() for the entity object (not value object), but I'm also afraid if the same operator (==) is not enough. So, the questions are: How does Hibernate know if a property of an object is changed? Do you suggest to override the hashCode()/equals() methods for complicated objects? What if they contains cyclic references? And, also, Would hashCode()/equals() with only the id field be enough?

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• Consing lists with user-defined type in Haskell

  - by user1319603

  I have this type I defined myself: data Item = Book String String String Int -- Title, Author, Year, Qty | Movie String String String Int -- Title, Director, Year, Qty | CD String String String Int deriving Show -- Title, Artist, Year, Qty I've created an empty list all_Items = [] With the following function I am trying to insert a new book of type Item (Book) into the all_Items addBook all_Items = do putStrLn "Enter the title of the book" tit <- getLine putStrLn "Enter the author of the book" aut <- getLine putStrLn "Enter the year this book was published" yr <- getLine putStrLn "Enter quantity of copies for this item in the inventory" qty <- getLine Book tit aut yr (read qty::Int):all_Items return(all_Items) I however am receiving this error: Couldn't match expected type `IO a0' with actual type `[a1]' The error points to the line where I am using the consing operator to add the new book to the list. I can gather that it is a type error but I can't figure out what it is that I am doing wrong and how to fix it. Thanks in Advance!

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• SQL vs MySQL: Rules about aggregate operations and GROUP BY

  - by Phazyck

  In this book I'm currently reading while following a course on databases, the following example of an illegal query using an aggregate operator is given: Find the name and age of the oldest sailor. Consider the following attempt to answer this query: SELECT S.name, S.age FROM Sailors.S The intent is for this query to return not only the maximum age but also the name of the sailors having that age. However, this query is illegal in SQL--if the SELECT clause uses an aggregate operation, then it must use only aggregate operations unless the query contains a GROUP BY clause! Some time later while doing an exercise using MySQL, I faced a similar problem, and made a mistake similar to the one mentioned. However, MySQL didn't complain and just spit out some tables which later turned out not be what I needed. Is the query above really illegal in SQL, but legal in MySQL, and if so, why is that? In what situation would one need to make such a query?

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• unexpected result from gnu sort

  - by funkycat

  when I try to sort the following text file 'input': test1 3 test3 2 test 4 with the command sort input the output is exactly the input. Here is the output of od -bc input : 0000000 164 145 163 164 061 011 063 012 164 145 163 164 063 011 062 012 t e s t 1 \t 3 \n t e s t 3 \t 2 \n 0000020 164 145 163 164 011 064 012 t e s t \t 4 \n 0000027 It's just a tab separated file with two columns. When I do sort -k 2 The output changes to test3 2 test1 3 test 4 which is what I would expect. But if I do sort -k 1 nothing changes with respect to the input, whereas I would expect 'test' to sort before 'test1'. Finally, if I do cat input | cut -f 1 | sort I get test test1 test3 as expected. Is there a logical explanation for this? What exactly is sort supposed to do by default, something like: sort -k 1 ? My version of sort: sort (GNU coreutils) 7.4

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• doubt in sizeof implementation

  - by aks

  Below is the program to find the size of a structure without using sizeof operator: struct MyStruct { int i; int j; }; int main() { struct MyStruct *p=0; int size = ((char*)(p+1))-((char*)p); printf("\nSIZE : [%d]\nSIZE : [%d]\n", size); return 0; } My doubt is: Why is typecasting to char * required? If I don't use the char* pointer, the output is 1 - WHY?

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• Getting Parent Layout in Qt

  - by Austin

  Hi, quick question. Is there any way to (easily) retrieve the parent layout of a widget in Qt? PS: QObject::parent() won't work, for logical reasons. EDIT: I'm positive the widget has a parent layout, because I added it to a layout earlier in the code. Now, I have many other layouts in the window and while it is possible for me to keep track of them, I just want to know if there is an easy and clean way to get the parent layout. EDIT2: Sorry, "easy and clean" was probably not the best way of putting. I meant using the Qt API. EDIT3: I'm adding the widget to the layout like this: QHBoxLayout* layout = new QHBoxLayout; layout-addWidget(button);

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