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  • Remove from a std::set<shared_ptr<T>> by T*

    - by Autopulated
    I have a set of shared pointers: std::set<boost::shared_ptr<T>> set; And a pointer: T* p; I would like to efficiently remove the element of set equal to p, but I can't do this with any of the members of set, or any of the standard algorithms, since T* is a completely different type to boost::shared_ptr<T>. A few approaches I can think of are: somehow constructing a new shared_ptr from the pointer that won't take ownership of the pointed to memory (ideal solution, but I can't see how to do this) wrapping / re-implementing shared_ptr so that I can do the above just doing my own binary search over the set Help!

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  • How I can use the HTTP headers to indicate in the Response that possibility?

    - by Cris Hong Kong CRISHK
    Finally I accomplished to cache dynamic images, css, and javascript files using HTTP headers BUT I have a problem now: I have specific dynamic images that are equal but has different URL's. For example: http://example.com/image/src/the-same-image.jpg http://example.com/image/custom/src/the-same-image2.jpg 1 and 2 has the same file content but different URL. This is a problem now because the navigator assumes that the file are different and need to be cached (due to the URL), when the real cached file is only one. I have the possibility to know if the file at the URL's are the same. How I can use the headers to indicate in the Response that possibility, and the navigator will cache only one file?

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  • Why does a C# System.Decimal remember trailing zeros?

    - by Rob Davey
    Is there a reason that a C# System.Decimal remembers the number of trailing zeros it was entered with? See the following example: public void DoSomething() { decimal dec1 = 0.5M; decimal dec2 = 0.50M; Console.WriteLine(dec1); //Output: 0.5 Console.WriteLine(dec2); //Output: 0.50 Console.WriteLine(dec1 == dec2); //Output: True } The decimals are classed as equal, yet dec2 remembers that it was entered with an additional zero. What is the reason/purpose for this?

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  • How do I do a join in ActiveRecord after records have been returned?

    - by Russ Bradberry
    I am using ActiveRecord in Rails 3 to pull data from two different tables in two different databases. These databases can not join on each other, but I have the need to do a simple join after-the-fact. I would like to preserve the relation so that I can chain it down the line. here is a simplified version of what I am doing browsers = Browser.all # <-- this is fairly small and can reside in memory events = Event.where(:row_date=>Date.today).select(:name, :browser_id) So as you can see, I want to join browsers in on the events relation, where browser_id should equal browsers.name. events is a relation and I can still add clauses to it down the line, so I dont want to run the query on the db just yet. How would I accomplish this?

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  • Prolog for beginners about logic and syntax

    - by lnotik
    Hello everybody. I have this question : I need to create a paradict "rightGuesses" which will get 3 arguments , each one of them is a list of letters : 1) The list of guessed letters 2) The word i have to guess 3) The letters that where guessed so far . for example : rightGuesses([n,o,p,q], [p,r,o,l,o,g], Ans). will give us Ans = [p, -, o, -, o, -]. i made: rightGuesses([],T2,[ANS]) rightGuesses([A|T1],T2,[ANS]):- (member(A,T2))=\=true , rightGuesses(T1,T2,[ _ |'-']). rightGuesses([A|T1],T2,[ANS]):- member(A,T2), rightGuesses(T1,T2,[ _ |A]). but i get : ERROR: c:/users/leonid/desktop/file3.pl:5:0: Syntax error: Operator expected Warning: c:/users/leonid/desktop/file3.pl:6: when i trying to compile it what is my problem , and is there is a better way to do it ? thanks in advance.

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  • Mutual Information / Entropy Calculation Help

    - by Fillip
    Hi, Hoping someone can give me some pointers with this entropy problem. Say X is chosen randomly from the uniform integer distribution 0-32 (inclusive). I calculate the entropy, H(X) = 32 bits, as each Xi has equal probability of occurring. Now, say the following pseudocode executes. int r = rand(0,1); // a random integer 0 or 1 r = r * 33 + X; How would I work out the mutual information between the two variables r and X? Mutual Information is defined as I(X; Y) = H(X) - H(X|Y) but I don't really understand how to apply the conditional entropy H(X|Y) to this problem. Thanks

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  • different explanation

    - by Delirium tremens
    The following code echoes 5, not 10: $global_obj = null; class my_class { var $value; function my_class() { global $global_obj; $global_obj = &$this; } } $a = new my_class; $a->my_value = 5; $global_obj->my_value = 10; echo $a->my_value; "Upon first examination, it would seem that the constructor of my_class stores a reference to itself inside the $global_obj variable. Therefore, one would expect that, when we later change the value of $global_obj-my_value to 10, the corresponding value in $a would change as well. Unfortunately, the new operator does not return a reference, but a copy of the newly created object." Please, give me a different explanation.

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  • Warning as Error - How to rid these

    - by coffeeaddict
    I cannot figure out how to get rid of errors that basically should not be halting my compile in VS 2010 and should not be show stoppers, or at least I will fix them later but I don't want the compile to just error and halt on these kinds of problems. For example I'm getting the following error: Error 1 Warning as Error: XML comment on 'ScrewTurn.Wiki.SearchEngine.Relevance.Finalize(float)' has a paramref tag for 'IsFinalized', but there is no parameter by that name C:\www\Wiki\Screwturn3_0_2_509\SearchEngine\Relevance.cs 60 70 SearchEngine for this code: /// /// Normalizes the relevance after finalization. /// /// The normalization factor. /// If is false ( was not called). public void NormalizeAfterFinalization(float factor) { if(factor < 0) throw new ArgumentOutOfRangeException("factor", "Factor must be greater than or equal to zero"); if(!isFinalized) throw new InvalidOperationException("Normalization can be performed only after finalization"); value = value * factor; } I looked in Tools | Options and I don't see where I can tweak the compiler and tell it not to worry about comment or XHTML based errors.

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  • Using unless in rails uniqueness validation

    - by dunxd
    I am just starting out in Rails, and trying to develop a simple application. I need to validate three values submitted to the application - each must meet the same validation criteria. The validation is pretty simple: Value is valid if unqiue, null or equal to "p" or "d". The following gets me halfway there: validates_uniqueness_of :value1, :value2, :value3, :allow_nil => true I think I can use :unless to check whether the value is either "p" or "d", however I can't figure out how. I guess I am trying to combine validates_uniqueness_of with validates_inclusion_of. Any suggestions?

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  • How to call a method withgin a vector?

    - by Mike Dooley
    Hi! How do I call a method of an object which is stored within a vector? The following code fails... ClassA* class_derived_a = new ClassDerivedA; ClassA* class_another_a = new ClassAnotherDerivedA; vector<ClassA*> test_vector; test_vector.push_back(class_derived_a); test_vector.push_back(class_another_a); for (vector<ClassA*>::iterator it = test_vector.begin(); it != test_vector.end(); it++) it->printOutput(); The code retrieves the following error: test3.cpp:47: error: request for member ‘printOutput’ in ‘* it.__gnu_cxx::__normal_iterator<_Iterator, _Container::operator- with _Iterator = ClassA**, _Container = std::vector ’, which is of non-class type ‘ClassA*’ The problem seems to be it->printOutput(); but at the moment I don't know how to call the method properly, does anyone know? regards mikey

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  • error: typedef name may not be a nested-name-specifier

    - by Autopulated
    I am trying to do something along the lines of this answer, and struggling: $ gcc --version gcc (GCC) 4.2.4 (Ubuntu 4.2.4-1ubuntu4) file.cpp:7: error: template argument 1 is invalid file.cpp:7: error: typedef name may not be a nested-name-specifier And the offending part of the file: template <class R, class C, class T0=void, class T1=void, class T2=void> struct MemberWrap; template <class R, class C, class T0> struct MemberWrap<R, C, T0>{ typedef R (C::*member_t)(T0); typedef typename boost::add_reference<typename T0>::type> TC0; // <---- offending line MemberWrap(member_t f) : m_wrapped(f){ } R operator()(C* p, TC0 p0){ GILRelease guard; return (p->*(this->m_wrapped))(p0); } member_t m_wrapped; };

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  • Is there an existing algorithm for this notation translation/conversion?

    - by John
    A system has a notation that would require writing an expression like (A+B)*C as #MUL(#ADD(A,B),C). Is there already an algorithm to do this kind of notation conversion so users can enter in a more conventional way? In other words an algorithm to convert from infix - my notation. First issue is I don't know an exact name for my notation... it's similar to reverse-polish but not quite. Every operator is encoded as a function taking arguments.

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  • Is there a concise way to create an InputSupplier for an InputStream in Google Guava?

    - by Fabian Steeg
    There are a few factory methods in Google Guava to create InputSuppliers, e.g. from a byte[]: ByteStreams.newInputStreamSupplier(bytes); Or from a File: Files.newInputStreamSupplier(file); Is there a similar way to to create an InputSupplier for a given InputStream? That is, a way that's more concise than an anonymous class: new InputSupplier<InputStream>() { public InputStream getInput() throws IOException { return inputStream; } }; Background: I'd like to use InputStreams with e.g. Files.copy(...) or ByteStreams.equal(...).

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  • Problem with literal arguments in the PATTERN string for a python 2to3 fixer

    - by Zxaos
    Hi folks. I'm writing a fixer for the 2to3 tool in python. In my pattern string, I have a section where I'd like to match an empty string as an argument, or an empty unicode string. The relevant chunk of my pattern looks like: (args='""' | args='u""') My issue is the second option never matches. Even if it's alone, it won't match. However, if I simply say args=any and then output args, I can catch cases where args is exactly equal to the second option. Is there some weird unicode handling thing going on? Why won't the second literal option ever match?

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  • Setting package-wide variables during python setup.py install

    - by Morgoth
    Is there a way that when a user types python setup.py install to install a Python package, setup.py can be made to set specific variables at the base of the pacakge? A common example would be to basically set mypackage.__revision__ to be the svn revision of the checkout if one is working from svn. Another example case would be if the user can choose a global option, so that the option mypackage.__option__ be set according to a flag passed to setup.py, e.g. python setup.py install --set-flag=10 Then when using the package, mypackage.__option__ would equal 10.

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  • Delete element from array

    - by Julio Diaz
    Is there a way I can get rid of some elements in an array. for instance, if i have this array int testArray[] = {0,2,0,3,0,4,5,6} Is there a "fast" way to get rid of the elements that equal 0 int resultArray[] = {2,3,4,5,6} I tried this function but I got lost using Lists public int[] getRidOfZero(int []s){ List<> result=new ArrayList<>(); for(int i=0; i<s.length; i++){ if(s[i]<0){ int temp = s[i]; result.add(temp); } } return result.toArray(new int[]); }

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  • What's the best way to return a random line in a text file using C?

    - by jeremy Ruten
    What's the best way to return a random line in a text file using C? It has to use the standard I/O library (<stdio.h>) because it's for Nintendo DS homebrew. Clarifications: Using a header in the file to store the number of lines won't work for what I want to do. I want it to be as random as possible (the best being if each line has an equal probability of being chosen as every other line.) The file will never change while the program is being run. (It's the DS, so no multi-tasking.)

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  • How to change rows in a table based on other table rows in mysql?

    - by understack
    I've a table which has 3 columns: id, a_id and b_id. Suppose rows are like this: 1, a1, b1 2, a1, b2 3, a1, b3 4, a2, b4 5, a2, b5 6, a2, b6 I want to convert it to 1, a1, b1 2, a1, b1 3, a1, b1 4, a2, b4 5, a2, b4 6, a2, b4 So I want to make all the b_id corresponding to a_id same, and equal to the one which is found first. How can I do this? For simplicity, I've removed other columns from table. So please ignore row duplication here.

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  • If-statement with logical OR

    - by exiter2000
    public class Test{ public static void main(String args[]){ int a = 0; int b = 1; int c = 10; if ( a == 0 || b++ == c ){ a = b + c; }else{ b = a + c; } System.out.println("a: " + a + ",b: " + b + ",c: " + c); } } Ok, this is Java code and the output is a: 11,b: 1,c: 10 And I believe the C acts same as Java in this case That is because second condition(b++ == c) would never executed if the first condition is true in 'OR' operator. There is a "NAME" for this. I just don't remember what it is. Does anyone know what this is called?? Thanks in advance

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  • How do I handle editing of custom types in a C# datagridview?

    - by Ian Hopkinson
    I have a datagridview in which one column contains a custom class, which I have set using: dgvPeriods.Columns[1].ValueType = typeof(ExDateTime); It is rigged up to display correctly by handling the CellFormatting event, but I'm unsure what event to handle for cell editing. In the absence of doing anything I get a FormatException as the datagridview tries to convert String to ExDateTime as I try to move focus out of the edited cell. I tried adding type conversion to my ExDateTime custom class: public static implicit operator ExDateTime(string b) { return new ExDateTime(b); } But this this didn't work. I also tried handling the DataError event, but this seems to fire too late. The datagridview is not databound.

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  • C++ Urban Myths

    - by Neil Butterworth
    I'm starting to write an article on what I'm calling "C++ Urban Myths" - that is, ideas and conceptions about C++ that are common but have no actual roots in reality. Some that I've come up with so far are: TR1 is part of standard C++ TR1 (technical Report #1) proposed a whole bunch of changes to C++. Unfortunately, it was never accepted. It is faster to use iterators to access a vector than operator[] Or vice versa. All tests I've carried out indicate the two are nearly identical in performance. The C++ Standard contains something called the STL It doesn't - neither "STL" nor "Standard Template Library" appear in the Standard. I'm wondering if the SO C++ community can come up with any better ones? Ideally, they should be expressible in a single sentence, and not involve any code. Edit: I guess I didn't make it clear enough that I was interested in myths believed by C++ developers, not misconceptions held by non-C++users. Oh well...

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  • SQL only row mapping record fetching

    - by Prasanna
    I have a customer call detail table in which call details of all customer stored. I have to find out the distinct aparty (means our customer ) who only calls our customers (means bparty also be our numbers) . There is no other domestic call , International calls made by A party (our customer) in this case. could you people please help me to find the same data. FILE INPUT oF SAMPLE CDR TABLE ROW NAME VALUES ANUMBER :-any mobile number(Domestic+International); for our customer it must like 70,070,0070,9370) BNUMBER :-any mobile number(Domestic+International); for our customer it must like 70,070,0070,9370 CALLTRANSACTION :-eg: 91,92,93 etc CALLTRANSACTIONTYPEC :-eg: MOC,MTC FILENAME :-MCS_01 etc TIME:- any time value Required Output DISTINCT ANUMBER :-for our customer it mobile number must start with 70 or 070 or 0070 or 9370 BNUMBER :- for our customer it mobile number must start with 70 or 070 or 0070 or 9370 means our customer only calls to our network customer ( No other doestic call or international calls made by our operator)

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  • How do you get the logical xor of two variables in Python?

    - by Zach Hirsch
    How do you get the logical xor of two variables in Python? For example, I have two variables that I expect to be strings. I want to test that only one of them contains a True value (is not None or the empty string): str1 = raw_input("Enter string one:") str2 = raw_input("Enter string two:") if logical_xor(str1, str2): print "ok" else: print "bad" The ^ operator seems to be bitwise, and not defined on all objects: >>> 1 ^ 1 0 >>> 2 ^ 1 3 >>> "abc" ^ "" Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unsupported operand type(s) for ^: 'str' and 'str'

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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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  • Distance between numpy arrays, columnwise

    - by Jaapsneep
    I have 2 arrays in 2D, where the column vectors are feature vectors. One array is of size F x A, the other of F x B, where A << B. As an example, for A = 2 and F = 3 (B can be anything): arr1 = np.array( [[1, 4], [2, 5], [3, 6]] ) arr2 = np.array( [[1, 4, 7, 10, ..], [2, 5, 8, 11, ..], [3, 6, 9, 12, ..]] ) I want to calculate the distance between arr1 and a fragment of arr2 that is of equal size (in this case, 3x2), for each possible fragment of arr2. The column vectors are independent of each other, so I believe I should calculate the distance between each column vector in arr1 and a collection of column vectors ranging from i to i + A from arr2 and take the sum of these distances (not sure though). Does numpy offer an efficient way of doing this, or will I have to take slices from the second array and, using another loop, calculate the distance between each column vector in arr1 and the corresponding column vector in the slice?

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