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  • Creating ostream manipulators for a specific class

    - by petersohn
    I have a class that is derived from ostream: class my_ostream: public std::ostream { // ... } I want to make a manipulator (for example do_something), that works specifically to this class, like this: my_ostream s; s << "some text" << do_something << "some more text"; I did the following: std::ostream &do_something(std::ostream &os) { my_ostream *s = dynamic_cast<my_ostream*>(&os); if (s != NULL) { // do something } return os; } This works, but is rather ugly. I tried the following: my_ostream &do_something(my_ostream &s) { // do something return s; } This doesn't work. I also tried another approach: class my_ostream: public std::ostream { // ... my_ostream &operator<<(const do_something & x) { // do something return *this; } } This still doesn't work.

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  • Binning into timeslots - Is there a better way than using list comp?

    - by flyingcrab
    I have a dataset of events (tweets to be specific) that I am trying to bin / discretize. The following code seems to work fine so far (assuming 100 bins): HOUR = timedelta(hours=1) start = datetime.datetime(2009,01,01) z = [dt + x*HOUR for x in xrange(1, 100)] But then, I came across this fateful line at python docs 'This makes possible an idiom for clustering a data series into n-length groups using zip(*[iter(s)]*n)'. The zip idiom does indeed work - but I can't understand how (what is the * operator for instance?). How could I use to make my code prettier? I'm guessing this means I should make a generator / iterable for time that yields the time in graduations of an HOUR?

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  • C++'s std::string pools, debug builds? std::string and valgrind problems

    - by Den.Jekk
    Hello, I have a problem with many valgrind warnings about possible memory leaks in std::string, like this one: 120 bytes in 4 blocks are possibly lost in loss record 4,192 of 4,687 at 0x4A06819: operator new(unsigned long) (vg_replace_malloc.c:230) by 0x383B89B8B0: std::string::_Rep::_S_create(unsigned long, unsigned long, std::allocator<char> const&) (in /usr/lib64/libstdc++.so.6.0.8) by 0x383B89C3B4: (within /usr/lib64/libstdc++.so.6.0.8) by 0x383B89C4A9: std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, unsigned long, std::allocator<char> const&) (in /usr/lib64/libstdc++.so.6.0.8) I'm wondering: does std::string (GCC 4.1.2) use any memory pools? if so, is there any way to disable the pools (in form of a debug build etc.)? Regards, Den

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  • functor returning 0

    - by Jon
    I've recently started teaching myself the standard template library. I was curious as to why the GetTotal() method in this class is returning 0? ... class Count { public: Count() : total(0){} void operator() (int val){ total += val;} int GetTotal() { return total;} private: int total; }; void main() { set<int> s; Count c; for(int i = 0; i < 10; i++) s.inset(i); for_each(s.begin(), s.end(), c); cout << c.GetTotal() << endl; }

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  • has any simply way to delete a value in list of python

    - by zjm1126
    a=[1,2,3,4] b=a.index(6) del a[b] print a it show error: Traceback (most recent call last): File "D:\zjm_code\a.py", line 6, in <module> b=a.index(6) ValueError: list.index(x): x not in list so i have to do this : a=[1,2,3,4] try: b=a.index(6) del a[b] except: pass print a but this is not simple,has any simply way ? thanks

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  • CompareValidator works in listview's editItemTemplate but not in insertitemtemplate

    - by Sam
    Hi, I have a validation problem I have a listview, in the edit item template I have two composite controls with a textbox inside I put a comparevalidator on it <asp:CompareValidator ID="myCompareValidator" runat="server" ControlToValidate="mycompositecontrol1" ControlToCompare="mycompositecontrol2" Operator="GreaterThanEqual" Type="Date" Display="Dynamic" ErrorMessage="there is an error !" Text="!" ValidationGroup="myValidationGroup" /> It works great ! so I do exactly the same operation in the InserItemTemplate (It's a copy/paste) but this time, it doesn't work, I have no error message in my validationsummary and near my control to validate! If you know that problem, help me please thanks in advance

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  • Aggregate functions in ANSI SQL

    - by morpheous
    I want to use multiple aggregate functions in a query. All the examples i have seem on aggregate functions however, are trivial. Typically, they are of the form: SELECT field1,agg_func1, agg_func2 GROUP BY SOME_COLUMNS HAVING agg_func1 OP SOME_SCALAR Where: OP: is a boolean operator (e.g. <, = etc) SOME_SCALAR: is a scalar (i.e. a constant number) What I want to know is if it is possible to write (IN ANSI SQL) queries like: SELECT field1,agg_func1, agg_func2, agg_func3 GROUP BY SOME_COLUMNS HAVING (agg_func1 OP1 agg_func2) OP2 (agg_func2 OP3 agg_func3) Where: OP[N] are boolean operators or ANSI SQL clause operators like 'BETWEEN', 'LIKE', 'IN' etc. Also, assuming this is possible (I have not seen any documentation saying otherwise) are there any efficiency/performance considerations (i.e. penalties) when the HAVING clause consists of a boolean expression combining the output of the aggregate functions - instead of the normal comparison of the output of the aggregate with a constant number (e.g. min('salary') 100 ) - which is often used in the most banal examples involving aggregate functions?

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  • How can I pull data from a SQL Database that spans an academic year?

    - by Eric Reynolds
    Basically, I want to pull data from August to May for a given set of dates. Using the between operator works as long as I do not cross the year marker (i.e. BETWEEN 8 AND 12 works -- BETWEEN 8 AND 5 does not). Is there any way to pull this data? Here is the SQL Query I wrote: SELECT count(*), MONTH(DateTime) FROM Downloads WHERE YEAR(DateTime) BETWEEN 2009 AND 2010 AND MONTH(DateTime) BETWEEN 8 AND 5 GROUP BY MONTH(DateTime) ORDER BY MONTH(DateTime)" Any help is appreciated. Thanks, Eric R.

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  • What is wrong with this SimPy installation?

    - by dmindreader
    Alright, I have tried a bunch of times the python setup.py install command from my command prompt, and this is what I'm getting: SCREEN And when trying this: from SimPy.Simulation import * on Idle, I get this: Traceback (most recent call last): File "C:/Python30/pruebas/prueba1", line 1, in <module> from SimPy.Simulation import * File "C:\Python30\SimPy\Simulation.py", line 320 print 'SimPy.Simulation %s' %__version__, ^ SyntaxError: invalid syntax >>>

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  • Why do all procedures have to be defined before the compiler sees them?

    - by incrediman
    For example, take a look at this code (from tspl4): (define proc1 (lambda (x y) (proc2 y x))) If I run this as my program in scheme... #!r6rs (import (rnrs)) (define proc1 (lambda (x y) (proc2 y x))) I get this error: expand: unbound identifier in module in: proc2 ...This code works fine though: #!r6rs (import (rnrs)) (define proc2 +) (define proc1 (lambda (x y) (proc2 y x))) (display (proc1 2 3)) ;output: 5

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  • installing opencv for python issues

    - by vlad
    I'm running OS X Leopard. I followed this site to install it. Trying to run any demo script, I now get "No module named opencv.cv", which is obviously stopping me from doing any programming. I am running python 2.5.1 (yes, I know it's kind of old). Why would this be, and how can I solve it? Thanks

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  • How Serializable works with insert in SQL Server 2005

    - by Spence
    G'day I think I have a misunderstanding of serializable. I have two tables (data, transaction) which I insert information into in a serializable transaction (either they are both in, or both out, but not in limbo). SET TRANSACTION ISOLATION LEVEL SERIALIZABLE BEGIN TRANSACTION INSERT INTO dbo.data (ID, data) VALUES (@Id, data) INSERT INTO dbo.transactions(ID, info) VALUES (@ID, @info) COMMIT TRANSACTION I have a reconcile query which checks the data table for entries where there is no transaction at read committed isolation level. INSERT INTO reconciles (ReconcileID, DataID) SELECT Reconcile = @ReconcileID, ID FROM Data WHERE NOT EXISTS (SELECT 1 FROM TRANSACTIONS WHERE data.id = transactions.id) Note that the ID is actually a composite (2 column) key, so I can't use a NOT IN operator My understanding was that the second query would exclude any values written into data without their transaction as this insert was happening at serializable and the read was occurring at read committed. I have evidence that reconcile is picking up entries

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  • Is this a correct implementation of singleton C++?

    - by Kamal
    class A{ static boost::shared_ptr<A> getInstance(){ if(pA==NULL){ pA = new A(); } return boost::shared_ptr(pA); } //destructor ~A(){ delete pA; pA=NULL; } private: A(){ //some initialization code } //private assigment and copy constructors A(A const& copy); // Not Implemented A& operator=(A const& copy); // Not Implemented static A* pA; }; A* A::pA = NULL;

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  • CVS list of files only in working directories

    - by Joshua Berry
    Is it possible to get a list of files that are in the working directory tree, but not in the current branch/tag? I currently diff the working copy with another directory updated to the same module and tag/branch but without the local non-repo files. It works, but doesn't honor the .cvsignore files. I figure there must be an option using a variation of 'cvs diff'. Thanks in advance.

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  • is this a simple monad example?

    - by zcaudate
    This is my attempt to grok monadic functions after watching http://channel9.msdn.com/Shows/Going+Deep/Brian-Beckman-Dont-fear-the-Monads. h uses bind to compose together two arbitrary functions f and g. What is the unit operator in this case? ;; f :: int - [str] ;; g :: str = [keyword] ;; bind :: [str] - (str - [keyword]) - [keyword] ;; h :: int - [keyword] (defn f [v] (map str (range v))) (defn g [s] (map keyword (repeat 4 s))) (defn bind [l f] (flatten (map f l))) (f 8) ;; = (0 1 2 3 4 5 6 7) (g "s") ;; = (:s :s :s :s) (defn h [v] (bind (f v) g)) (h 9) ;; = (:0 :0 :0 :0 :1 :1 :1 :1 :2 :2 :2 :2 :3 :3 :3 :3 :4 :4 :4 :4 :5 :5 :5 :5)

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  • Blit Queue Optimization Algorithm

    - by martona
    I'm looking to implement a module that manages a blit queue. There's a single surface, and portions of this surface (bounded by rectangles) are copied to elsewhere within the surface: add_blt(rect src, point dst); There can be any number of operations posted, in order, to the queue. Eventually the user of the queue will stop posting blits, and ask for an optimal set of operations to actually perform on the surface. The task of the module is to ensure that no pixel is copied unnecessarily. This gets tricky because of overlaps of course. A blit could re-blit a previously copied pixel. Ideally blit operations would be subdivided in the optimization phase in such a way that every block goes to its final place with a single operation. It's tricky but not impossible to put this together. I'm just trying to not reinvent the wheel. I looked around on the 'net, and the only thing I found was the SDL_BlitPool Library which assumes that the source surface differs from the destination. It also does a lot of grunt work, seemingly unnecessarily: regions and similar building blocks are a given. I'm looking for something higher-level. Of course, I'm not going to look a gift horse in the mouth, and I also don't mind doing actual work... If someone can come forward with a basic idea that makes this problem seem less complex than it does right now, that'd be awesome too. EDIT: Thinking about aaronasterling's answer... could this work? Implement customized region handler code that can maintain metadata for every rectangle it contains. When the region handler splits up a rectangle, it will automatically associate the metadata of this rectangle with the resulting sub-rectangles. When the optimization run starts, create an empty region handled by the above customized code, call this the master region Iterate through the blt queue, and for every entry: Let srcrect be the source rectangle for the blt beng examined Get the intersection of srcrect and master region into temp region Remove temp region from master region, so master region no longer covers temp region Promote srcrect to a region (srcrgn) and subtract temp region from it Offset temp region and srcrgn with the vector of the current blt: their union will cover the destination area of the current blt Add to master region all rects in temp region, retaining the original source metadata (step one of adding the current blt to the master region) Add to master region all rects in srcrgn, adding the source information for the current blt (step two of adding the current blt to the master region) Optimize master region by checking if adjacent sub-rectangles that are merge candidates have the same metadata. Two sub-rectangles are merge candidates if (r1.x1 == r2.x1 && r1.x2 == r2.x2) | (r1.y1 == r2.y1 && r1.y2 == r2.y2). If yes, combine them. Enumerate master region's sub-rectangles. Every rectangle returned is an optimized blt operation destination. The associated metadata is the blt operation`s source.

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  • Lazy evaluation with ostream C++ operators

    - by SavinG
    I am looking for a portable way to implement lazy evaluation in C++ for logging class. Let's say that I have a simple logging function like void syslog(int priority, const char *format, ...); then in syslog() function we can do: if (priority < current_priority) return; so we never actually call the formatting function (sprintf). On the other hand, if we use logging stream like log << LOG_NOTICE << "test " << 123; all the formating is always executed, which may take a lot of time. Is there any possibility to actually use all the goodies of ostream (like custom << operator for classes, type safety, elegant syntax...) in a way that the formating is executed AFTER the logging level is checked ?

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  • LINQ-to-SQL: Searching against a CSV

    - by Peter Bridger
    I'm using LINQtoSQL and I want to return a list of matching records for a CSV contains a list of IDs to match. The following code is my starting point, having turned a CSV string in a string array, then into a generic list (which I thought LINQ would like) - but it doesn't: Error Error 22 Operator '==' cannot be applied to operands of type 'int' and 'System.Collections.Generic.List<int>' C:\Documents and Settings\....\Search.cs 41 42 C:\...\ Code DataContext db = new DataContext(); List<int> geographyList = new List<int>( Convert.ToInt32(geography.Split(',')) ); var geographyMatches = from cg in db.ContactGeographies where cg.GeographyId == geographyList select new { cg.ContactId }; Where do I go from here?

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  • A python code to convert a number from any base to the base of 10 giving errors . What is wrong with this code?

    - by mekasperasky
    import math def baseencode(number, base): ##Converting a number of any base to base10 if number == 0: return '0' for i in range(0,len(number)): if number[i]!= [A-Z]: num = num + number[i]*pow(i,base) else : num = num + (9 + ord(number[i])) *pow(i,base) return num a = baseencode('20',5) print a Errors I get are Traceback (most recent call last): File "doubtrob.py", line 19, in <module> a = baseencode('20',5) File "doubtrob.py", line 13, in baseencode if number[i]!= [A-Z]: NameError: global name 'A' is not defined

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  • NASM shift operators

    - by Hudson Worden
    How would you go about doing a bit shift in NASM on a register? I read the manual and it only seems to mention these operators , <<. When I try to use them NASM complains about the shift operator working on scalar values. Can you explain what a scalar value is and give an example of how to use and <<. Also, I thought there were a shr or shl operators. If they do exist can you give an example of how to use them? Thank you for your time.

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  • How to use a object whose copy constructor and copy assignment is private?

    - by coanor
    In reading TCPL, I got a problem, as the title refered, and then 'private' class is: class Unique_handle { private: Unique_handle& operator=(const Unique_handle &rhs); Unique_handle(const Unique_handle &rhs); public: //... }; the using code is: struct Y { //... Unique_handle obj; }; and I want to execute such operations: int main() { Y y1; Y y2 = y1; } although, these code are come from TCPL, but I still can not got the solution... Can anybody help me, appreciate.

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  • Bipartite matching in Python

    - by vailen
    Does anybody know any module in Python that computes the best bipartite matching? I have tried the following two: munkres hungarian However, in my case, I have to deal with non-complete graph (i.e., there might not be an edge between two nodes), and therefore, there might not be a match if the node has no edge. The above two packages seem not to be able to deal with this. Any advice?

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