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• C# logic order and compiler behavior

  - by Terrapin

  In C#, (and feel free to answer for other languages), what order does the runtime evaluate a logic statement? Example: DataTable myDt = new DataTable(); if (myDt != null && myDt.Rows.Count > 0) { //do some stuff with myDt } Which statement does the runtime evaluate first - myDt != null or: myDt.Rows.Count > 0 ? Is there a time when the compiler would ever evaluate the statement backwards? Perhaps when an "OR" operator is involved?

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• Best way to validate currency input?

  - by Abe Miessler

  I have created the TextBox and CompareValidator below which I thought would allow input in the following forms: 5 5.00 $5.00 Unfortunately it's not allowing the version with the dollar sign in it. What is the point of doing a type check against currency if you don't allow the dollar sign? Is there a way to allow this symbol? <asp:TextBox ID="tb_CostShare" runat="server" Text='<%# Eval("CostShare", "{0:$0.00}")%>' CausesValidation="true" /> <asp:CompareValidator ID="vld_CostShare" runat="server" ControlToValidate="tb_CostShare" Operator="DataTypeCheck" Type="Currency" ValidationGroup="vld" ErrorMessage="You must enter a dollar amount for 'Cost Share'." />

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• What is the best solution to replace a new memory allocator in an existing code?

  - by O. Askari

  During the last few days I've gained some information about memory allocators other than the standard malloc(). There are some implementations that seem to be much better than malloc() for applications with many threads. For example it seems that tcmalloc and ptmalloc have better performance. I have a C++ application that uses both malloc and new operators in many places. I thought replacing them with something like ptmalloc may improve its performance. But I wonder how does the new operator act when used in C++ application that runs on Linux? Does it use the standard behavior of malloc or something else? What is the best way to replace the new memory allocator with the old one in the code? Is there any way to override the behavior or new and malloc or do I need to replace all the calls to them one by one?

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• C++ / Java: Toggle boolean statement?

  - by Martijn Courteaux

  Hi, Is there a short way to toggle a boolean? With integers we can do operations like this: int i = 4; i *= 4; // equals 16 /* Which is equivalent to */ i = i * 4; So is there also something for booleans (like the *= operator for ints)? In C++: bool booleanWithAVeryLongName = true; booleanWithAVeryLongName = !booleanWithAVeryLongName; // Can it shorter? booleanWithAVeryLongName !=; // Or something? In Java: boolean booleanWithAVeryLongName = true; booleanWithAVeryLongName = !booleanWithAVeryLongName; // Can it shorter? booleanWithAVeryLongName !=; // Or something?

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• Is call to 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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• How to declare a pointer to a variable as a parameter of a function in C++?

  - by Keand64

  I have a function that takes a pointer to a D3DXVECTOR3, but I have no reason to declare this beforehand. The most logical solution to me was using new: Function( //other parameters, new D3DXVECTOR3(x, y, 0)); but I don't know how I would go about deleting it, beign intitialized in a function. My next thought was to use the & operator, like so: Function( //other parameters, &D3DVECTOR3(x, y, 0)); but I don't know if this is a valid way to go about doing this. (It doesn't get an error, but neither does int *x; x = 50;). So should I use new, &, or some other technique I'm overlooking?

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• Access SQL query to SELECT from one table and INSERT into another

  - by typoknig

  Below is my query. Access does not like it, giving me the error Syntax error (missing operator) in query expression 'answer WHERE question = 1'. Hopefully you can see what I am trying to do. Please pay particular attention to 3rd, 4th, and 5th lines under the SELECT statement. INSERT INTO Table2 (respondent,1,2,3-1,3-2,3-3,4,5) SELECT respondent, answer WHERE question = 1, answer WHERE question = 2, answer WHERE answer = 'text 1' AND question = 3, answer WHERE answer = 'text 2' AND question = 3, answer WHERE answer = 'text 3' AND question = 3, answer WHERE question = 4, longanswer WHERE question 5 FROM Table1 GROUP BY respondent;

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• Fulltext search not returning expected results

  - by Puneet

  I am experimenting with SQL Server full text search. I have a simple Categories table with Id as the primary key: CREATE TABLE [dbo].[Category]( [Id] [int] IDENTITY(1,1) NOT NULL, [CategoryName] [varchar](100) NOT NULL, ) My Query is: SELECT * FROM FREETEXTTABLE (Category, CategoryName, 'music') AS F INNER JOIN Category C ON F.[Key] = C.Id ORDER BY F.Rank DESC This returns me several records with the word music in them, but it does NOT return any record with word ‘musical’. Although, it can be said that the string being searched is not very big and using the LIKE operator will resolve it. I would like to use fulltext search because this simple example is going to be extended to include other tables and fileds.

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• JavaScript eval() with `this`

  - by mojuba

  If I define a JavaScript code snippet in my HTML, like so: <div id=myElem onMyUpdate="alert('Update called for ' + this.id)">... then what is the most elegant way of evaluating it from within JavaScript with this properly assigned? What I came up with so far is something like this: if (elem.hasAttribute('onMyUpdate')) (function () { eval(elem.getAttribute('onMyUpdate')) }).call(elem); which looks terrible (to me), but works. Any better/more elegant alternatives? MDN says there used to be the second argument to eval() for doing just that but it's deprecated now; MDN then suggests to use operator with() instead, which, if you follow the link provided, turns out to be made deprecated by the latest standard. Dead end, in other words. (As a side note, StackOverflow ignores the word this in search terms and thus it may miss relevant answers - is there a way of telling it not to?) Edit: I forgot to mention: no jQuery please, just vanilla JavaScript

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• I serialized a C++ object, how to allocate memory for it without knowing what type it is?

  - by Neo_b

  Hello, I have serialized a C++ object and I wish to allocate space for it, although I can't use the "new" operator, because I do not know the object's class. I tried using malloc(sizeof(object)), although trying to typecast the pointer to the type the serialized object is of, the program shut down. Where is the information about the object class stored? class object { public: virtual void somefunc(); int someint; }; class objectchild:public object { } object *o=(object*)malloc(sizeof(objectchild)); cout << int(dynamic_cast<objectchild*>(o)) << endl; This causes a program shutdown. Thank you in advance.

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• RegularExpressionValidator always fails, but ValidationExpression works in testing

  - by Jerph

  I found the answer to this, but it's a bit of a gotcha so I wanted to share it here. I have a regular expression that validates passwords. They should be 7 to 60 characters with at least one numeric and one alpha character. Pretty standard. I used positive lookaheads (the (?= operator) to implement it: (?=^.{7,60}$)(?=.*[0-9].*)(?=.*[a-zA-Z].*) I checked this expression in my unit tests using Regex.IsMatch(), and it worked fine. However, when I use it in a RegularExpressionValidator, it always fails. Why?

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• Is it possible to have a variadic function in C with no non-variadic parameter?

  - by Tim

  I have the following function: void doStuff(int unusedParameter, ...) { va_list params; va_start(params, unusedParameter); /* ... */ va_end(params); } As part of a refactor, I'd like to remove the unused parameter without otherwise changing the implementation of the function. As far as I can tell, it's impossible to use va_start when you don't have a last non-variadic parameter to refer to. Is there any way around this? Background: It is in fact a C++ program, so I could use some operator-overloading magic as suggested here, but I was hoping not to have to change the interface at this point. The existing function does its work by requiring that the variable argument list be null-terminated, and scanning for the NULL, therefore it doesn't need a leading argument to tell it how many arguments it has.

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• ActionScript: Using 'in' on protected/private variables?

  - by David Wolever

  Is there any way to mimic the in operator, but testing for the existence of protected or private fields? For example, this: <mx:Script><![CDATA[ public var pub:Boolean = true; protected var prot:Boolean = true; private var priv:Boolean = true; ]]></mx:Script> <mx:creationComplete><![CDATA[ for each (var prop in ["pub", "prot", "priv", "bad"]) trace(prop + ":", prop in this); ]]></mx:creationComplete> Will trace: pub: true prot: false priv: false bad: false When I want to see: pub: true prot: true priv: true bad: false

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• deleting dynamically allocated object that contains vector in C++ STL

  - by kobac

  I have a class class ChartLine{ protected: vector<Point> line; // points connecting the line CString name; //line name for legend CPen pen; //color, size and style properties of the line }; where Point is a structure struct Point{ CString x; double y; }; In main() I dynamically allocate objects of type ChartLine with new operator. If I use delete afterwards, will default destructor ~ChartLine() properly dealocate (or clear) member ChartLine::line(which is vector btw) or I would have to clear that vector in ~ChartLine() manually? Thanks in advance. Cheers.

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• How do I do division on HH:MM:SS format time strings in C#?

  - by Jake

  I have a series of times that are coming to me as strings from a web service. The times are formated as HH:MM:SS:000 (3 milisecond digits). I need to compare two times to determine if one is more than twice as long as the other: if ( timeA / timeB > 2 ) What's the simplest way to work with the time strings? If I was writing in Python this would be the answer to my question: Difference between two time intervals in Python Edit: What I'm really looking for is a way to get the ratio of timeA to timeB, which requires division, not subtraction. Unfortunately, the DateTime structure doesn't appear to have a division operator. Updated the question title to reflect this.

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• How do I iterate over a tuple

  - by Caligo

  How can I iterate over a tuple starting from, say, index 1 to 2? The following doesn't work. using boost::fusion::cons; typedef cons<A, cons<B, cons<C, cons<D> > > > MyTuple; MyTuple tuple_; template <class T> struct DoSomething{ DoSomething(T& t) : t_(&t){ } template <class U> void operator()(U u){ boost::fusion::at<mpl::int_<u> >(*t_); } T* t_; }; boost::mpl::for_each< boost::mpl::range_c<int, 1, 3> >( DoSomething<MyTuple>(tuple_) );

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• How to retrieve all keys (or values) from a std::map?

  - by Owen

  This is one of the possible ways I come out: struct RetrieveKey { template <typename T> typename T::first_type operator()(T keyValuePair) const { return keyValuePair.first; } }; map<int, int> m; vector<int> keys; // Retrieve all keys transform(m.begin(), m.end(), back_inserter(keys), RetrieveKey()); // Dump all keys copy(keys.begin(), keys.end(), ostream_iterator<int>(cout, "\n")); Of course, we can also retrieve all values from the map by defining another functor RetrieveValues. Is there any other way to achieve this easily? (I'm always wondering why std::map does not include a member function for us to do so.)

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• How to insert into std::map.

  - by Knowing me knowing you

  In code below: map<string,vector<int>> create(ifstream& in, const vector<string>& vec) { /*holds string and line numbers into which each string appears*/ typedef map<string,vector<int>> myMap; typedef vector<string>::const_iterator const_iter; myMap result; string tmp; unsigned int lineCounter = 0; while(std::getline(in,tmp)) { const_iter beg = vec.begin(); const_iter end = vec.end(); while (beg < end) { if ( tmp.find(*beg) != string::npos) { result[*beg].push_back(lineCounter);//THIS IS THE LINE I'M ASKING FOR } ++beg; } ++lineCounter; } return result; } How should I do it (check line commented in code) if I want to use insert method of map instead of using operator[]? Thank you.

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• Any way to make a generic List where I can add a type AND a subtype?

  - by user383178

  I understand why I cannot do the following: private class Parent { }; private class Child extends Parent { }; private class GrandChild extends Child { }; public void wontCompile(List<? extends Parent> genericList, Child itemToAdd) { genericList.add(itemToAdd); } My question is there ANY practical way to have a typesafe List where you can call add(E) where E is known to be only a Parent or a Child? I vaguely remember some use of the "|" operator as used for wildcard bounds, but I cannot find it in the spec... Thanks!

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• C++: Vector3 type "wall" ?

  - by anon

  Say I have: class Vector3 { float x, y, z; ... bunch of cuntions .. static operator+(const Vector3&, const Vector3); }; Now, suppose I want to have classes: Position, Velocity, that are exactly like Vector3 (basically, I want typedef Vector3 Position; typedef Vector3 Velocity; Except, given: Position position; Vector3 vector3; Velocity velocity; I want to make sure the following can't happen: position + vector3; vector3 + velocity; velocity + position; What is the best way to achieve this?

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• How should I get Xcode to link an iOS project that uses a C++ static library

  - by user1681572

  Using Xcode, I've written a Cocoa Touch static library, mainly in C++. It exposes a C interface for the benefit of Objective-C client code. I have a client iOS app that uses it, and everything works and runs as expected, except that I found I needed to include a minimal .cpp file in the client project to get the link to succeed. Otherwise I get C++-related unresolved symbols, e.g. operator new(unsigned long). The above hack is easy and effective, and so I guess I'm not breaking any laws, but is there a proper way to eliminate my linker errors?

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• C pointer question, dereferencing crash

  - by skynorth

  Why do this work? int *var; while(scanf("%d", &var) && *var != 0) printf("%d \n", var); While this does not? int *var; while(scanf("%d", &var) && var != 0) printf("%d \n", var); Doesn't * (dereference operator) give you the value pointed by the pointer? So why does *var != 0 crash the program, while var != 0 does not?

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• How do I put logic in a View a scope or method in a Model?

  - by Angela

  I have the following in the view: <% unless contact_email.statuses.empty?%> (<%= contact_email.statuses.find(:last).status%>) <% end %> contact_email is an instance of a specific model. Could I do something like this? class ContactEmail < ActiveRecord::Base attr_accessible :contact_id, :email_id, :status, :subject, :body, :date_created, :date_sent def status unless contact_email.statuses.empty? contact_email.statuses.find(:last).status end end end is there a better way to do this? is there a way to use the || operator for a default if empty? Basically, I would like to be able to do the following in the View: <%= contact_email.status = IF there is a value, then display it, if not, show nothing.

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• Using Linq to filter parents by their children

  - by Nick L

  Having some problems with my Silverlight app (with RIA services) filtering my results. The idea is on the client I set up the EntityQuery and its filters and call load. However this isn't working for me. Heres my code. public void FireQuery(string filterValue) { EntityQuery<Parent> query = m_ParentDomainContext.GetParentQuery(); query = query.Where(p => p.Children.Any(c => c.Name.Contains(filterValue))); m_ParentDomainContext.Load(query, Query_Completed, null); } Compiles just fine, however, runtime I get "Query operator 'Any' is not supported." Exception. Does anyone know of a good way to filter like this? Again, I'm looking for a way to set this up on the client.

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• What does it mean when a Perl method returns a "hashref"?

  - by Uri

  I'm trying to decrypt a Perl code which I'm not familiar with, somehow related to HashRef. I'm using Amazon::S3, but my question is a general Perl question. See the code below: use Amazon::S3; my $s3 = Amazon::S3->new( ... ); my $response = $s3->buckets; Documentation (here) sais, about s3-buckets: Returns undef on error, else HASHREF of results The following line is working for me, but I don't understand why: for $b in ( @ { $response->{buckets} } ) { print "bucket: " . $b->bucket . "\n"; } I'm Puzzled by each operator on the first line. What type exactly are $response, $respone->{bucket}. Looks like the expression within the for is an array, but I don't understand this syntax: @{ ... }?

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