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C++ error: expected initializer before ‘&’ token

- by Werner

Hi, the following piece of C++ code compiled two years ago in a suse 10.1 Linux machine. #ifndef DATA_H #define DATA_H #include <iostream> #include <iomanip> inline double sqr(double x) { return x*x; } enum Direction { X,Y,Z }; inline Direction next(const Direction d) { switch(d) { case X: return Y; case Y: return Z; case Z: return X; } } inline ostream& operator<<(ostream& os,const Direction d) { switch(d) { case X: return os << "X"; case Y: return os << "Y"; case Z: return os << "Z"; } } ... ... Now, I am trying to compile it on Ubuntu 9.10 and I get the error: data.h:20: error: expected initializer before ‘&’ token which is referred to the line of: inline ostream& operator<<(ostream& os,const Direction d) the g++ used on this machine is: Using built-in specs. Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.4.1-4ubuntu9' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --program-suffix=-4.4 --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --disable-werror --with-arch-32=i486 --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu Thread model: posix gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu9) Could you give me some hint about this error? Thanks

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Deserialize complex JSON (VB.NET)

- by Ssstefan

I'm trying to deserialize json returned by some directions API similar to Google Maps API. My JSON is as follows (I'm using VB.NET 2008): jsontext = { "version":0.3, "status":0, "route_summary": { "total_distance":300, "total_time":14, "start_point":"43", "end_point":"42" }, "route_geometry":[[51.025421,18.647631],[51.026131,18.6471],[51.027802,18.645639]], "route_instructions": [["Head northwest on 43",88,0,4,"88 m","NW",334.8],["Continue on 42",212,1,10,"0.2 km","NW",331.1,"C",356.3]] } So far I came up with the following code: Dim js As New System.Web.Script.Serialization.JavaScriptSerializer Dim lstTextAreas As Output_CloudMade() = js.Deserialize(Of Output_CloudMade())(jsontext) I'm not sure how to define complex class, i.e. Output_CloudMade. I'm trying something like: Public Class RouteSummary Private mTotalDist As Long Private mTotalTime As Long Private mStartPoint As String Private mEndPoint As String Public Property TotalDist() As Long Get Return mTotalDist End Get Set(ByVal value As Long) mTotalDist = value End Set End Property Public Property TotalTime() As Long Get Return mTotalTime End Get Set(ByVal value As Long) mTotalTime = value End Set End Property Public Property StartPoint() As String Get Return mStartPoint End Get Set(ByVal value As String) mStartPoint = value End Set End Property Public Property EndPoint() As String Get Return mEndPoint End Get Set(ByVal value As String) mEndPoint = value End Set End Property End Class Public Class Output_CloudMade Private mVersion As Double Private mStatus As Long Private mRSummary As RouteSummary 'Private mRGeometry As RouteGeometry 'Private mRInstructions As RouteInstructions Public Property Version() As Double Get Return mVersion End Get Set(ByVal value As Double) mVersion = value End Set End Property Public Property Status() As Long Get Return mStatus End Get Set(ByVal value As Long) mStatus = value End Set End Property Public Property Summary() As RouteSummary Get Return mRSummary End Get Set(ByVal value As RouteSummary) mRSummary = value End Set End Property 'Public Property Geometry() As String ' Get ' End Get ' Set(ByVal value As String) ' End Set 'End Property 'Public Property Instructions() As String ' Get ' End Get ' Set(ByVal value As String) ' End Set 'End Property End Class but it does not work. The problem is with complex properties, like route_summary. It is filled with "nothing". Other properties, like "status" or "version" are filled properly. Any ideas, how to define class for the above JSON? Can you share some working code for deserializing JSON in VB.NET? Thanks,

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C# reflection instantiation

- by NickLarsen

I am currently trying to create a generic instance factory for which takes an interface as the generic parameter (enforced in the constructor) and then lets you get instantiated objects which implement that interface from all types in all loaded assemblies. The current implementation is as follows: public class InstantiationFactory { protected Type Type { get; set; } public InstantiationFactory() { this.Type = typeof(T); if (!this.Type.IsInterface) { // is there a more descriptive exception to throw? throw new ArgumentException(/* Crafty message */); } } public IEnumerable GetLoadedTypes() { // this line of code found in other stack overflow questions var types = AppDomain.CurrentDomain.GetAssemblies() .SelectMany(a = a.GetTypes()) .Where(/* lambda to identify instantiable types which implement this interface */); return types; } public IEnumerable GetImplementations(IEnumerable types) { var implementations = types.Where(/* lambda to identify instantiable types which implement this interface */ .Select(x = CreateInstance(x)); return implementations; } public IEnumerable GetLoadedImplementations() { var loadedTypes = GetLoadedTypes(); var implementations = GetImplementations(loadedTypes); return implementations; } private T CreateInstance(Type type) { T instance = default(T); var constructor = type.GetConstructor(Type.EmptyTypes); if (/* valid to instantiate test */) { object constructed = constructor.Invoke(null); instance = (T)constructed; } return instance; } } It seems useful to me to have my CreateInstance(Type) function implemented as an extension method so I can reuse it later and simplify the code of my factory, but I can't figure out how to return a strongly typed value from that extension method. I realize I could just return an object: public static class TypeExtensions { public object CreateInstance(this Type type) { var constructor = type.GetConstructor(Type.EmptyTypes); return /* valid to instantiate test */ ? constructor.Invoke(null) : null; } } Is it possible to have an extension method create a signature per instance of the type it extends? My perfect code would be this, which avoids having to cast the result of the call to CreateInstance(): Type type = typeof(MyParameterlessConstructorImplementingType); MyParameterlessConstructorImplementingType usable = type.CreateInstance();

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How can I find out if two arguments are instances of the same, but unknown class?

- by Ingmar

Let us say we have a method which accepts two arguments o1 and o2 of type Object and returns a boolean value. I want this method to return true only when the arguments are instances of the same class, e.g.: foo(new Integer(4),new Integer(5)); Should return true, however: foo(new SomeClass(), new SubtypeSomeClass()); should return false and also: foo(new Integer(3),"zoo"); should return false. I believe one way is to compare the fully qualified class names: public boolean foo(Object o1, Object o2){ Class<? extends Object> c1 = o1.getClass(); Class<? extends Object> c2 = o2.getClass(); if(c1.getName().equals(c2.getName()){ return true;} return false; } An alternative conditional statement would be : if (c1.isAssignableFrom(c2) && c2.isAssignableFrom(c1)){ return true; } The latter alternative is rather slow. Are there other alternatives to this problem?

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How to detect whether there is a specific member variable in class?

- by Kirill V. Lyadvinsky

For creating algorithm template function I need to know whether x or X (and y or Y) in class that is template argument. It may by useful when using my function for MFC CPoint class or GDI+ PointF class or some others. All of them use different x in them. My solution could be reduces to the following code: template<int> struct TT {typedef int type;}; template<class P> bool Check_x(P p, typename TT<sizeof(&P::x)>::type b = 0) { return true; } template<class P> bool Check_x(P p, typename TT<sizeof(&P::X)>::type b = 0) { return false; } struct P1 {int x; }; struct P2 {float X; }; // it also could be struct P3 {unknown_type X; }; int main() { P1 p1 = {1}; P2 p2 = {1}; Check_x(p1); // must return true Check_x(p2); // must return false return 0; } But it does not compile in Visual Studio, while compiling in the GNU C++. With Visual Studio I could use the following template: template<class P> bool Check_x(P p, typename TT<&P::x==&P::x>::type b = 0) { return true; } template<class P> bool Check_x(P p, typename TT<&P::X==&P::X>::type b = 0) { return false; } But it does not compile in GNU C++. Is there universal solution? UPD: Structures P1 and P2 here are only for example. There are could be any classes with unknown members.

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How to add validation errors in the validation collection asp.net mvc?

- by johndoe

Inside my controller's action I have the following code: public ActionResult GridAction(string id) { if (String.IsNullOrEmpty(id)) { // add errors to the errors collection and then return the view saying that you cannot select the dropdownlist value with the "Please Select" option } return View(); UPDATE: if (String.IsNullOrEmpty(id)) { // add error ModelState.AddModelError("GridActionDropDownList", "Please select an option"); return RedirectToAction("Orders"); } } UPDATE 2: Here is my updated code: @Html.DropDownListFor(x => x.SelectedGridAction, Model.GridActions,"Please Select") @Html.ValidationMessageFor(x => x.SelectedGridAction) The Model looks like the following: public class MyInvoicesViewModel { private List<SelectListItem> _gridActions; public int CurrentGridAction { get; set; } [Required(ErrorMessage = "Please select an option")] public string SelectedGridAction { get; set; } public List<SelectListItem> GridActions { get { _gridActions = new List<SelectListItem>(); _gridActions.Add(new SelectListItem() { Text = "Export to Excel", Value = "1"}); return _gridActions; } } } And here is my controller action: public ActionResult GridAction(string id) { if (String.IsNullOrEmpty(id)) { // add error ModelState.AddModelError("SelectedGridAction", "Please select an option"); return RedirectToAction("Orders"); } return View(); } Nothing happens! I am totally lost on this one! UPDATE 3: I am now using the following code but still the validation is not firing: public ActionResult GridAction(string id) { var myViewModel= new MyViewModel(); myViewModel.SelectedGridAction = id; // id is passed as null if (!ModelState.IsValid) { return View("Orders"); }

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Why overload true and false instead of defining bool operator?

- by Joe Enos

I've been reading about overloading true and false in C#, and I think I understand the basic difference between this and defining a bool operator. The example I see around is something like: public static bool operator true(Foo foo) { return (foo.PropA > 0); } public static bool operator false(Foo foo) { return (foo.PropA <= 0); } To me, this is the same as saying: public static implicit operator bool(Foo foo) { return (foo.PropA > 0); } The difference, as far as I can tell, is that by defining true and false separately, you can have an object that is both true and false, or neither true nor false: public static bool operator true(Foo foo) { return true; } public static bool operator false(Foo foo) { return true; } //or public static bool operator true(Foo foo) { return false; } public static bool operator false(Foo foo) { return false; } I'm sure there's a reason this is allowed, but I just can't think of what it is. To me, if you want an object to be able to be converted to true or false, a single bool operator makes the most sense. Can anyone give me a scenario where it makes sense to do it the other way? Thanks

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usort - more parameters

- by pgfonline

Hallo, how can I pass more parameters to usort? I have different functions, which are very similar in structure, I want to have just one function: <?php $arr = array( array('number' => 100, 'string'=>'aaa'), array('number'=>50, 'string'=>'bdef'), array('number'=>150, 'string'=>'cbba') ); usort($arr, 'sortNumberDesc'); //How can I use just a single function? //How can I pass further parameters to usort? function sortNumberDesc($a, $b){ $a = $a['number']; $b = $b['number']; if ($a == $b) return 0; return ($a > $b) ? -1 : +1; } function sortNumberAsc($a, $b){ $a = $a['number']; $b = $b['number']; if ($a == $b) return 0; return ($a < $b) ? -1 : +1; } //I want to do the same with just one function: //Sort ID is the search index, reverse DESC or ASC function sort($a, $b, $sortId='number', $reverse = 0){ $a = $a[$sortId]; $b = $b[$sortId]; if ($a == $b) return 0; if($reverse == false) return ($a > $b) ? -1 : +1; else return ($a < $b) ? -1 : +1; } print_r($arr); ?>

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Is there a way to implement Caliburn-like co-routines in VB.NET since there's no yield keyword

- by Miroslav Popovic

Note that I'm aware of other yield in vb.net questions here on SO. I'm playing around with Caliburn lately. Bunch of great stuff there, including co-routines implementation. Most of the work I'm doing is C# based, but now I'm also creating an architecture guideline for a VB.NET only shop, based on Rob's small MVVM framework. Everything looks very well except using co-routines from VB. Since VB 10 is used, we can try something like Bill McCarthy's suggestion: Public Function Lines(ByVal rdr as TextReader) As IEnumerable(Of String) Return New GenericIterator(Of String) (Function(ByRef nextItem As String) As Boolean nextItem = rdr.ReadLine Return nextItem IsNot Nothing End Function) End Function I'm just failing to comprehend how a little more complex co-routine method like the one below (taken from Rob's GameLibrary) could be written in VB: public IEnumerable<IResult> ExecuteSearch() { var search = new SearchGames { SearchText = SearchText }.AsResult(); yield return Show.Busy(); yield return search; var resultCount = search.Response.Count(); if (resultCount == 0) SearchResults = _noResults.WithTitle(SearchText); else if (resultCount == 1 && search.Response.First().Title == SearchText) { var getGame = new GetGame { Id = search.Response.First().Id }.AsResult(); yield return getGame; yield return Show.Screen<ExploreGameViewModel>() .Configured(x => x.WithGame(getGame.Response)); } else SearchResults = _results.With(search.Response); yield return Show.NotBusy(); } Any idea how to achieve that, or any thoughts on using Caliburn co-routines in VB?

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JSON feed to Java Object

- by mnml

Hi, I would like to know if there is a webpage/software that can "translate" a Json feed object to a Java object with attributes. For example : { 'firstName': 'John', 'lastName': 'Smith', 'address': { 'streetAddress': '21 2nd Street', 'city': 'New York' } } Would become: class Person { private String firstName; private String lastName; private Address address; public String getFirstName() { return firstName; } public String getLastName() { return lastName; } public Address getAddress() { return address; } public void setFirstName(String firstName) { this.firstName = firstName; } public void setLastName(String lastName) { this.lastName = lastName; } public void setAddress(Address address) { this.address = address; } public String toString() { return String.format("firstName: %s, lastName: %s, address: [%s]", firstName, lastName, address); } } class Address { private String streetAddress; private String city; public String getStreetAddress() { return streetAddress; } public String getCity() { return city; } public void setStreetAddress(String streetAddress) { this.streetAddress = streetAddress; } public void setCity(String city) { this.city = city; } public String toString() { return String.format("streetAddress: %s, city: %s", streetAddress, city); } } I'm not asking that because I'm lazy, but the JSON I would like to parse has quite a lot of attribute.

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Incorrect logic flow? function that gets coordinates for a sudoku game

- by igor

This function of mine keeps on failing an autograder, I am trying to figure out if there is a problem with its logic flow? Any thoughts? Basically, if the row is wrong, "invalid row" should be printed, and clearInput(); called, and return false. When y is wrong, "invalid column" printed, and clearInput(); called and return false. When both are wrong, only "invalid row" is to be printed (and still clearInput and return false. Obviously when row and y are correct, print no error and return true. My function gets through most of the test cases, but fails towards the end, I'm a little lost as to why. bool getCoords(int & x, int & y) { char row; bool noError=true; cin>>row>>y; row=toupper(row); if(row>='A' && row<='I' && isalpha(row) && y>=1 && y<=9) { x=row-'A'; y=y-1; return true; } else if(!(row>='A' && row<='I')) { cout<<"Invalid row"<<endl; noError=false; clearInput(); return false; } else { if(noError) { cout<<"Invalid column"<<endl; } clearInput(); return false; } }

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[grails] setting cookies when render type is "contentType: text/json"

- by Robin Jamieson

Is it possible to set cookies on response when the return render type is set as json? I can set cookies on the response object when returning with a standard render type and later on, I'm able to get it back on the subsequent request. However, if I were to set the cookies while rendering the return values as json, I can't seem to get back the cookie on the next request object. What's happening here? These two actions work as expected with 'basicForm' performing a regular form post to the action, 'withRegularSubmit', when the user clicks submit. // first action set the cookie and second action yields the originally set cookie def regularAction = { // using cookie plugin response.setCookie("username-regular", "regularCookieUser123",604800); return render(view: "basicForm"); } // called by form post def withRegularSubmit = { def myCookie = request.getCookie("username-regular"); // returns the value 'regularCookieUser123' return render(view: "resultView"); } When I switch to setting the cookie just before returning from the response with json, I don't get the cookie back with the post. The request starts by getting an html document that contains a form and when doc load event is fired, the following request is invoked via javascript with jQuery like this: var someUrl = "http://localhost/jsonAction"; $.get(someUrl, function(jsonData) { // do some work with javascript} The controller work: // this action is called initially and returns an html doc with a form. def loadJsonForm = { return render(view: "jsonForm"); } // called via javascript when the document load event is fired def jsonAction = { response.setCookie("username-json", "jsonCookieUser456",604800); // using cookie plugin return render(contentType:'text/json') { 'pair'('myKey': "someValue") }; } // called by form post def withJsonSubmit = { def myCookie = request.getCookie("username-json"); // got null value, expecting: jsonCookieUser456 return render(view: "resultView"); } The data is returned to the server as a result of the user pressing the 'submit' button and not through a script. Prior to the submit of both 'withRegularSubmit' and 'withJsonSubmit', I see the cookies stored in the browser (Firefox) so I know they reached the client.

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Recursive Maze in Java

- by Api

I have written a short Java code for solving a simple maze problem to go from S to G. I do not understand where the problem is going wrong. import java.util.Scanner; public class tester { static char [][] grid={ {'.','.'}, {'.','.'}, {'S','G'}, }; static int a=2; static int b=2; static boolean findpath(int x, int y) { if((x > grid.length-1) || (y > grid[0].length-1) || (x < 0 || y < 0)) { return false; } else if(x==a && y==b){ return true; } else if (findpath(x,y-1) == true){ return true; } else if (findpath(x+1,y) == true){ return true; } else if (findpath(x,y+1) == true) { return true; } else if (findpath(x-1,y) == true){ return true; } return false; } public static void main(String[] args){ boolean result=findpath(2,0); System.out.print(result); } } I am giving the starting position directly and goal is defined in a & b. Do help.

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Generate syntax tree for simple math operations

- by M28

I am trying to generate a syntax tree, for a given string with simple math operators (+, -, *, /, and parenthesis). Given the string "1 + 2 * 3": It should return an array like this: ["+", [1, ["*", [2,3] ] ] ] I made a function to transform "1 + 2 * 3" in [1,"+",2,"*",3]. The problem is: I have no idea to give priority to certain operations. My code is: function isNumber(ch){ switch (ch) { case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': case '.': return true; break; default: return false; break; } } function generateSyntaxTree(text){ if (typeof text != 'string') return []; var code = text.replace(new RegExp("[ \t\r\n\v\f]", "gm"), ""); var codeArray = []; var syntaxTree = []; // Put it in its on scope (function(){ var lastPos = 0; var wasNum = false; for (var i = 0; i < code.length; i++) { var cChar = code[i]; if (isNumber(cChar)) { if (!wasNum) { if (i != 0) { codeArray.push(code.slice(lastPos, i)); } lastPos = i; wasNum = true; } } else { if (wasNum) { var n = Number(code.slice(lastPos, i)); if (isNaN(n)) { throw new Error("Invalid Number"); return []; } else { codeArray.push(n); } wasNum = false; lastPos = i; } } } if (wasNum) { var n = Number(code.slice(lastPos, code.length)); if (isNaN(n)) { throw new Error("Invalid Number"); return []; } else { codeArray.push(n); } } })(); // At this moment, codeArray = [1,"+",2,"*",3] return syntaxTree; } alert('Returned: ' + generateSyntaxTree("1 + 2 * 3"));

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Is there any appreciable difference between if and if-else?

- by Drew

Given the following code snippets, is there any appreciable difference? public boolean foo(int input) { if(input > 10) { doStuff(); return true; } if(input == 0) { doOtherStuff(); return true; } return false; } vs. public boolean foo(int input) { if(input > 10) { doStuff(); return true; } else if(input == 0) { doOtherStuff(); return true; } else { return false; } } Or would the single exit principle be better here with this piece of code... public boolean foo(int input) { boolean toBeReturned = false; if(input > 10) { doStuff(); toBeReturned = true; } else if(input == 0) { doOtherStuff(); toBeReturned = true; } return toBeReturned; } Is there any perceptible performance difference? Do you feel one is more or less maintainable/readable than the others?

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Custom Django Field is deciding to work as ForiegnKey for no reason

- by Joe Simpson

Hi, i'm making a custom field in Django. There's a problem while trying to save it, it's supposed to save values like this 'user 5' and 'status 9' but instead in the database these fields show up as just the number. Here is the code for the field: def find_key(dic, val): return [k for k, v in dic.items() if v == val][0] class ConnectionField(models.TextField): __metaclass__ = models.SubfieldBase serialize = False description = 'Provides a connection for an object like User, Page, Group etc.' def to_python(self, value): if type(value) != unicode: return value value = value.split(" ") if value[0] == "user": return User.objects.get(pk=value[1]) else: from social.models import connections return get_object_or_404(connections[value[0]], pk=value[1]) def get_prep_value(self, value): from social.models import connections print value, "prep" if type(value) == User: return "user %s" % str(value.pk) elif type(value) in connections.values(): o= "%s %s" % (find_key(connections, type(value)), str(value.pk)) print o, "return" return o else: print "CONNECTION ERROR!" raise TypeError("Value is not connectable!") Connection is just a dictionary with the "status" text linked up to the model for a StatusUpdate. I'm saving a model like this which is causing the issue: Relationship.objects.get_or_create(type="feedback",from_user=request.user,to_user=item) Please can someone help, Many Thanks Joe *_*

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How to highlight the new created file in JTree

- by newbie123

I want to make it like when I click a button, it will create a new file. Then the jTree will highlight the new file. Below are my code. Currently I create new file, i will show the new file but no highlight the file. class FileTreeModel implements TreeModel { private FileNode root; public FileTreeModel(String directory) { root = new FileNode(directory); } public Object getRoot() { return root; } public Object getChild(Object parent, int index) { FileNode parentNode = (FileNode) parent; return new FileNode(parentNode, parentNode.listFiles()[index].getName()); } public int getChildCount(Object parent) { FileNode parentNode = (FileNode) parent; if (parent == null || !parentNode.isDirectory() || parentNode.listFiles() == null) { return 0; } return parentNode.listFiles().length; } public boolean isLeaf(Object node) { return (getChildCount(node) == 0); } public int getIndexOfChild(Object parent, Object child) { FileNode parentNode = (FileNode) parent; FileNode childNode = (FileNode) child; return Arrays.asList(parentNode.list()).indexOf(childNode.getName()); } public void valueForPathChanged(TreePath path, Object newValue) { } public void addTreeModelListener(TreeModelListener l) { } public void removeTreeModelListener(TreeModelListener l) { } } class FileNode extends java.io.File { public FileNode(String directory) { super(directory); } public FileNode(FileNode parent, String child) { super(parent, child); } @Override public String toString() { return getName(); } } jTree = new JTree(); jTree.setBounds(new Rectangle(164, 66, 180, 421)); jTree.setBackground(SystemColor.inactiveCaptionBorder); jTree.setBorder(BorderFactory.createTitledBorder(null, "", TitledBorder.LEADING, TitledBorder.TOP, new Font("Arial", Font.BOLD, 12), new Color(0, 0, 0))); FileTreeModel model = new FileTreeModel(root); jTree.setRootVisible(false); jTree.setModel(model); expandAll(jTree); public void expandAll(JTree tree) { int row = 0; while (row < tree.getRowCount()) { tree.expandRow(row); row++; } }

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Derived interface from generic method

- by Sunit

I'm trying to do this: public interface IVirtualInterface{ } public interface IFabricationInfo : IVirtualInterface { int Type { get; set; } int Requirement { get; set; } } public interface ICoatingInfo : IVirtualInterface { int Type { get; set; } int Requirement { get; set; } } public class FabInfo : IFabricationInfo { public int Requirement { get { return 1; } set { } } public int Type { get {return 1;} set{} } } public class CoatInfo : ICoatingInfo { public int Type { get { return 1; } set { } } public int Requirement { get { return 1; } set { } } } public class BusinessObj { public T VirtualInterface<T>() where T : IVirtualInterface { Type targetInterface = typeof(T); if (targetInterface.IsAssignableFrom(typeof(IFabricationInfo))) { var oFI = new FabInfo(); return (T)oFI; } if (targetInterface.IsAssignableFrom(typeof(ICoatingInfo))) { var oCI = new CoatInfo(); return (T)oCI; } return default(T); } } But getting a compiler error: Canot convert type 'GenericIntf.FabInfo' to T How do I fix this? thanks Sunit

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Can't iterate over a list class in Python

- by Vicky

I'm trying to write a simple GUI front end for Plurk using pyplurk. I have successfully got it to create the API connection, log in, and retrieve and display a list of friends. Now I'm trying to retrieve and display a list of Plurks. pyplurk provides a GetNewPlurks function as follows: def GetNewPlurks(self, since): '''Get new plurks since the specified time. Args: since: [datetime.datetime] the timestamp criterion. Returns: A PlurkPostList object or None. ''' offset = jsonizer.conv_datetime(since) status_code, result = self._CallAPI('/Polling/getPlurks', offset=offset) return None if status_code != 200 else \ PlurkPostList(result['plurks'], result['plurk_users'].values()) As you can see this returns a PlurkPostList, which in turn is defined as follows: class PlurkPostList: '''A list of plurks and the set of users that posted them.''' def __init__(self, plurk_json_list, user_json_list=[]): self._plurks = [PlurkPost(p) for p in plurk_json_list] self._users = [PlurkUser(u) for u in user_json_list] def __iter__(self): return self._plurks def GetUsers(self): return self._users def __eq__(self, other): if other.__class__ != PlurkPostList: return False if self._plurks != other._plurks: return False if self._users != other._users: return False return True Now I expected to be able to do something like this: api = plurk_api_urllib2.PlurkAPI(open('api.key').read().strip(), debug_level=1) plurkproxy = PlurkProxy(api, json.loads) user = plurkproxy.Login('my_user', 'my_pass') ps = plurkproxy.GetNewPlurks(datetime.datetime(2009, 12, 12, 0, 0, 0)) print ps for p in ps: print str(p) When I run this, what I actually get is: <plurk.PlurkPostList instance at 0x01E8D738> from the "print ps", then: for p in ps: TypeError: __iter__ returned non-iterator of type 'list' I don't understand - surely a list is iterable? Where am I going wrong - how do I access the Plurks in the PlurkPostList?

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Can someone tell me what this Java class does? I/O related

- by anon

I am relatively new to Java and trying to learn the I/O syntax. Could someone give me a general overview of what this code does? Thanks!! import java.io.*; public class FileReader { private String openFile=""; private String saveFile=""; FileReader(openFile, saveFile) { this.openFile=openFile; this.saveFile=saveFile; } public String process(){ System.out.println(this.openFile); System.out.println(this.saveFile); BufferedReader open=null; FileReader openFR=null; FileWriter save=null; int counter=0; String output=""; if(openFile.equals("")){ return "No open file specifified\n"; } if(this.saveFile.equals("")){ return "No save file specified\n"; } try { openFR = new FileReader(this.openFile); open = new BufferedReader(openFR); } catch (FileNotFoundException e) { return ("Open file no longer exists\n"); } try { save = new FileWriter(saveFile); } catch (IOException e){ return ("Error saving the file\n"); } try{ String temp = open.readLine(); while(temp != null){ temp = open.readLine(); counter++; save.write(output + "\n"); } } catch (IOException e){ e.getStackTrace(); return ("Error reading open file"); } try { save.flush(); } catch (IOException e) { e.printStackTrace(); return ("Error writing save file"); } return "Operation completed successfully"; } }

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Why is calling close() after fopen() not closing?

- by Richard Morgan

I ran across the following code in one of our in-house dlls and I am trying to understand the behavior it was showing: long GetFD(long* fd, const char* fileName, const char* mode) { string fileMode; if (strlen(mode) == 0 || tolower(mode[0]) == 'w' || tolower(mode[0]) == 'o') fileMode = string("w"); else if (tolower(mode[0]) == 'a') fileMode = string("a"); else if (tolower(mode[0]) == 'r') fileMode = string("r"); else return -1; FILE* ofp; ofp = fopen(fileName, fileMode.c_str()); if (! ofp) return -1; *fd = (long)_fileno(ofp); if (*fd < 0) return -1; return 0; } long CloseFD(long fd) { close((int)fd); return 0; } After repeated calling of GetFD with the appropriate CloseFD, the whole dll would no longer be able to do any file IO. I wrote a tester program and found that I could GetFD 509 times, but the 510th time would error. Using Process Explorer, the number of Handles did not increase. So it seems that the dll is reaching the limit for the number of open files; setting _setmaxstdio(2048) does increase the amount of times we can call GetFD. Obviously, the close() is working quite right. After a bit of searching, I replaced the fopen() call with: long GetFD(long* fd, const char* fileName, const char* mode) { *fd = (long)open(fileName, 2); if (*fd < 0) return -1; return 0; } Now, repeatedly calling GetFD/CloseFD works. What is going on here?

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NUnit doesn't work well with Assert.AreEqual

- by stasal

Hi! I'm new to unit-testing and NUit in particular. I'm just typing some examples from the book which refers to Java and JUnit. But I'm using C# instead. The problem is: I've got a class with overriden methods such as Equals() and GetHashCode(), but when I am trying to compare two objects of this class with Assert.AreEqual() my code is not called, so I get an exception. Assert.True(MyClass.Equals(MyClass2)) does work well. But I don't wanna use this construction instead of Assert.AreEqual(). Where the problem can be? Here is the class: public class Money { public int amount; protected string currency; public Money(int amount, string currency) { this.amount = amount; this.currency = currency; } public new bool Equals(object obj) { if (obj == null) return false; Money money = (Money)obj; return (amount == money.amount) && (Currency().Equals(money.Currency())); } public new int GetHashCode() { return (string.Format("{0}{1}", amount, currency)).GetHashCode(); } public static Money Dollar(int amount) { return new Money(amount, "USD"); } public static Money Franc(int amount) { return new Money(amount, "CHF"); } public Money Times(int multiplier) { return new Money(amount * multiplier, currency); } public string Currency() { return currency; } } And the test method itself: [TestFixture] public class DollarTest { [Test] public void TestMultiplication() { Money five = Money.Dollar(5); Assert.True(Money.Dollar(10).Equals(five.Times(2))); // ok Assert.AreEqual(Money.Dollar(10), five.Times(2)); // fails } } Thanks.

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What does this structure actually do?

- by LGTrader

I found this structure code in a Julia Set example from a book on CUDA. I'm a newbie C programmer and cannot get my head around what it's doing, nor have I found the right thing to read on the web to clear it up. Here's the structure: struct cuComplex { float r; float i; cuComplex( float a, float b ) : r(a), i(b) {} float magnitude2( void ) { return r * r + i * i; } cuComplex operator*(const cuComplex& a) { return cuComplex(r*a.r - i*a.i, i*a.r + r*a.i); } cuComplex operator+(const cuComplex& a) { return cuComplex(r+a.r, i+a.i); } }; and it's called very simply like this: cuComplex c(-0.8, 0.156); cuComplex a(jx, jy); int i = 0; for (i=0; i<200; i++) { a = a * a + c; if (a.magnitude2() > 1000) return 0; } return 1; So, the code did what? Defined something of structure type 'cuComplex' giving the real and imaginary parts of a number. (-0.8 & 0.156) What is getting returned? (Or placed in the structure?) How do I work through the logic of the operator stuff in the struct to understand what is actually calculated and held there? I think that it's probably doing recursive calls back into the stucture float magnitude2 (void) { return return r * r + i * i; } probably calls the '*' operator for r and again for i, and then the results of those two operations call the '+' operator? Is this correct and what gets returned at each step? Just plain confused. Thanks!

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Android ArrayList<Location> passing between activities

- by squixy

I have simple class Track, which stores information about route: import java.io.Serializable; import java.util.ArrayList; import java.util.Date; import android.location.Location; public class Track implements Serializable { private static final long serialVersionUID = -5317697499269650204L; private Date date; private String name; private int time; private double distance, speed; private ArrayList<Location> route; public Track(String name, int time, double distance, ArrayList<Location> route) { this.date = new Date(); this.name = name; this.time = time; this.distance = distance; this.speed = distance / (time / 3600.); this.route = route; } public String getDate() { return String.format("Date: %1$td-%1$tb-%1$tY%nTime: %1$tH:%1$tM:%1$tS", date); } public String getName() { return name; } public int getTime() { return time; } public double getDistance() { return distance; } public float getSpeed() { return (float) speed; } public ArrayList<Location> getRoute() { return route; } @Override public String toString() { return String.format("Name: %s%nDate: %2$td-%2$tb-%2$tY%nTime: %2$tH:%2$tM:%2$tS", name, date); } } And I'm passing it from one activity to another: Intent showTrackIntent = new Intent(TabSavedActivity.this, ShowTrackActivity.class); showTrackIntent.putExtra("track", adapter.getItem(position)); startActivity(showTrackIntent); Where (Track object is element on ListView). I get error during passing Track object: java.lang.RuntimeException: Parcelable encountered IOException writing serializable object (name = classes.Track) What is happening?

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libcurl (c api) READFUNCTION for http PUT blocking forever

- by Duane

I am using libcurl for a RESTful library. I am having two problems with a PUT message, I am just trying to send a small content like "hello" via put. My READFUNCTION for PUT's blocks for a very large amount of time (minutes) when I follow the manual at curl.haxx.se and return a 0 indicating I have finished the content. (on os X) When I return something 0 this succeeds much faster (< 1 sec) When I run this on my linux machine (ubuntu 10.4) this blocking event appears to NEVER return when I return 0, if I change the behavior to return the size written libcurl appends all the data in the http body sending way more data and it fails with a "too much data" message from the server. my readfunction is below, any help would be greatly appreciated. I am using libcurl 7.20.1 typedef struct{ void *data; int body_size; int bytes_remaining; int bytes_written; } postdata; size_t readfunc(void *ptr, size_t size, size_t nmemb, void *stream) { if(stream) { postdata ud = (postdata)stream; if(ud->bytes_remaining) { if(ud->body_size > size*nmemb) { memcpy(ptr, ud->data+ud->bytes_written, size*nmemb); ud->bytes_written+=size+nmemb; ud->bytes_remaining = ud->body_size-size*nmemb; return size*nmemb; } else { memcpy(ptr, ud->data+ud->bytes_written, ud->bytes_remaining); ud->bytes_remaining=0; return 0; } }

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