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• String comparison in Python: is vs. ==

  - by Coquelicot

  I noticed a Python script I was writing was acting squirrelly, and traced it to an infinite loop, where the loop condition was "while line is not ''". Running through it in the debugger, it turned out that line was in fact ''. When I changed it to != rather than 'is not', it worked fine. I did some searching, and found this question, the top answer to which seemed to be just what I needed. Except the answer it gave was counter to my experience. Specifically, the answerer wrote: For all built-in Python objects (like strings, lists, dicts, functions, etc.), if x is y, then x==y is also True. I double-checked the type of the variable, and it was in fact of type str (not unicode or something). Is his answer just wrong, or is there something else afoot? Also, is it generally considered better to just use '==' by default, even when comparing int or Boolean values? I've always liked to use 'is' because I find it more aesthetically pleasing and pythonic (which is how I fell into this trap...), but I wonder if it's intended to just be reserved for when you care about finding two objects with the same id.

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• Making a button click and process using javascript with Asp.Net

  - by user944919

  I'm having two buttons and one button is hidden. Now when I click the visible button I need to do two things 1.Open Iframe. 2.Automatically make the 2nd Button(Hidden)to be clicked. When the second button is clicked I need to display the message on top of the IFrame which I have mentioned as function showStickySuccessToast() Now I am able to open IFrame but I'm unable to make the Hidden button clicked automatically. This is what I'm having: <script type="text/javascript"> $(document).ready(function(){ $("#<%=Button1.ClientID%>").click(function(event){ $('#<%=TextBox1.ClientID%>').change(function () { $('#various3').attr('href', $(this).val()); }); }); function showStickySuccessToast() { $().toastmessage('showToast', { text: 'Finished Processing!', sticky: false, position: 'middle-center', type: 'success', closeText: '', close: function () { } }); } }) </script> Here are my two buttons how I'm working with: <a id="various3" href="#"><asp:Button ID="Button1" runat="server" Text="Button" OnClientClick="Button2_Click"/></a> <asp:Button ID="Button2" runat="server" Text="Button" Visible="False" OnClick="Button2_Click"/> And in the button2_Click event: Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click System.Web.UI.ScriptManager.RegisterClientScriptBlock(Page, GetType(Page), "Script", "showStickySuccessToast();", True) End Sub

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• Rails: include index with fields_for form helper

  - by Patrick Oscity

  i'm trying to build two models from one form by using the fields_for method. my code looks like this: <% for scale in @event.scales %> <% f.fields_for "scale[]", scale do |scale_form| %> <p> Scale<br /> <%= scale_form.label :name %> <%= scale_form.text_field :name %> <%= scale_form.label :price %> <%= scale_form.text_field :price %> </p> <% end %> <% end %> but unfortunately the output html is missing the id's of the scales: <p> Scale<br /> <label for="event_scale__name">Name</label> <input id="event_scale__name" name="event[scale][][name]" size="30" type="text" /> <label for="event_scale__price">Price</label> <input id="event_scale__price" name="event[scale][][price]" size="30" type="text" /> </p> ... here's the corresponding controller and model: class EventsController < ApplicationController ... def new @event = Event.new @providers = Provider.find(:all, :order => :name) 3.times { @event.scales.build } respond_to do |format| format.html end end ... end class Event < ActiveRecord::Base has_many :scales ... end what am i doing wrong?

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• No grammar constraints (DTD or XML schema) detected for the document.

  - by fastcodejava

  I have this dtd : http://fast-code.sourceforge.net/template.dtd But when I include in an xml I get the warning : No grammar constraints (DTD or XML schema) detected for the document. The xml is : <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE templates PUBLIC "//UNKNOWN/" "http://fast-code.sourceforge.net/template.dtd"> <templates> <template type="type"> <description>Some</description> <variation></variation> <variation-field></variation-field> <allow-multiple-variation></allow-multiple-variation> <class-pattern></class-pattern> <getter-setter>setter</getter-setter> <allowed-file-extensions>java</allowed-file-extensions> <number-required-classes>1</number-required-classes> <template-body> <![CDATA[ Some Data ]]> </template-body> </template> </templates> Any clue?

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• Show a PDF file to the user with perl or php, not creating it nor download it. Just show it.

  - by dimassony

  Hello guys. I want to show my users PDF files. The reason why I use cgi to show the pdf is I want to track the clicks for the pdf, and cloak the real location of the saved pdf. I've been searching on the Internet and only found how to show save dialog to the users and creating a pdf, not show the files to the users. What I wanted for is show the users my pdf files, not creating or download the pdf. Here is what I got form the official php documentation: <?php header('Content-type: application/pdf'); readfile('the.pdf'); ?> Also my google-search-result perl code: open(PDF, "the.pdf") or die "could not open PDF [$!]"; binmode PDF; my $output = do { local $/; <PDF> }; close (PDF); print "Content-Type: application/pdf\n"; print "Content-Length: " .length($output) . "\n\n"; print $output if you do it on ruby, please say it to me. But I'm not sure if my server support rails. Sorry if my code is too far away from the method to show the pdf, since I don't know anything about pdf processing and how to implement this problem. Lets assume that the users have the Adobe Reader plug-in. So, how to fix my problem?

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• Python: eliminating stack traces into library code?

  - by Mark Harrison

  When I get a runtime exception from the standard library, it's almost always a problem in my code and not in the library code. Is there a way to truncate the exception stack trace so that it doesn't show the guts of the library package? For example, I would like to get this: Traceback (most recent call last): File "./lmd3-mkhead.py", line 71, in <module> main() File "./lmd3-mkhead.py", line 66, in main create() File "./lmd3-mkhead.py", line 41, in create headver1[depotFile]=rev TypeError: Data values must be of type string or None. and not this: Traceback (most recent call last): File "./lmd3-mkhead.py", line 71, in <module> main() File "./lmd3-mkhead.py", line 66, in main create() File "./lmd3-mkhead.py", line 41, in create headver1[depotFile]=rev File "/usr/anim/modsquad/oses/fc11/lib/python2.6/bsddb/__init__.py", line 276, in __setitem__ _DeadlockWrap(wrapF) # self.db[key] = value File "/usr/anim/modsquad/oses/fc11/lib/python2.6/bsddb/dbutils.py", line 68, in DeadlockWrap return function(*_args, **_kwargs) File "/usr/anim/modsquad/oses/fc11/lib/python2.6/bsddb/__init__.py", line 275, in wrapF self.db[key] = value TypeError: Data values must be of type string or None.

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• Eclipse BIRT - Unnecessary inline style with external CSS when rendering HTML

  - by Etienne

  Hello! I am designing a report using external CSS with BIRT 2.5. When BIRT renders the html report, it creates copies of each external style to inline styles (name style_x) in the resulting html. The report.design contains: <list-property name="cssStyleSheets"> <structure> <property name="fileName">… mycss.css</property> <property name="externalCssURI"> http://.../mycss.css </property> </structure> </list-property> The resulting html contains: <style type="text/css"> .style_0 {…} .style_1 {…} …. </style> <link rel="stylesheet" type="text/css" href="http://.../mycss.css"></link> For each reference of my styles, the rendered html elements use both styles usually like this: <div class="style_x myclass" …. > …. </div> Is there any way to get rid of the useless inline styles when rendering html?

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• $().buttonset not working on dialog modal box JQUERY

  - by vikitor

  Hello everyone! I've done a dialog box that contains a form inside it, and I would like to add some jquery fancy items to it. I've been trying with $().buttonset() as I've done with most of my radio buttons in the application, in order to get a coherent IU for my application. The thing is that, even if following the rules specified, the buttons remain as a normal radio button, and not with the fancy interface. Do you know what could be the problem? This is the part of the form where I want the fancy radio buttons: <div id ="Replace"> <input type="radio" name="Replace" value = "true" id = "ReplaceYes" onclick = "setReplace(this)" /> <label for="ReplaceYes">Yes</label> <input type="radio" name="Replace" value = "false" checked="checked" id = "ReplaceNo" onclick = "setReplace(this)" /> <label for="ReplaceNo">No</label> </div> And then, as the previous part of code is in a partial view, invoked when showing the modal box, this is how I try to convert the buttons appearance: $("#Replace").buttonset(); The thing is that, debugging it I've seen that it goes through that part of the code, but it doesn't do what it's meant to do. Any clue? Thanks everyone for your attention, vikitor

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• Does F# documentation have a way to search for functions by their types?

  - by Nathan Sanders

  Say I want to know if F# has a library function of type ('T -> bool) -> 'T list -> int ie, something that counts how many items of a list that a function returns true for. (or returns the index of the first item that returns true) I used to use the big list at the MSR site for F# before the documentation on MSDN was ready. I could just search the page for the above text because the types were listed. But now the MSDN documentation only lists types on the individual pages--the module page is a mush of descriptive text. Google kinda-sorta works, but it can't help with // compatible interfaces ('T -> bool) -> Seq<'T> -> int // argument-swaps Seq<'T> -> ('T -> bool) -> int // type-variable names ('a -> bool) -> Seq<'a> -> int // wrappers ('a -> bool) -> 'a list -> option<int> // uncurried versions ('T -> bool) * 'T list -> int // .NET generic syntax ('T -> bool) -> List<'T> -> int // methods List<'T> member : ('T -> bool) -> int Haskell has a standalone program for this called Hoogle. Does F# have an equivalent, like Fing or something?

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• Javascript function with PHP throwing a "Illegally Formed XML Syntax" error

  - by Joe

  I'm trying to learn some javascript and i'm having trouble figuring out why my code is incorrect (i'm sure i'm doing something wrong lol), but anyways I am trying to create a login page so that when the form is submitted javascript will call a function that checks if the login is in a mysql database and then checks the validity of the password for the user if they exist. however I am getting an error (Illegally Formed XML Syntax) i cannot resolve. I'm really confused, mostly because netbeans is saying it is a xml syntax error and i'm not using xml. here is the code in question: function validateLogin(login){ login.addEventListener("input", function() { $value = login.value; if (<?php //connect to mysql mysql_connect(host, user, pass) or die(mysql_error()); echo("<script type='text/javascript'>"); echo("alert('MYSQL Connected.');"); echo("</script>"); //select db mysql_select_db() or die(mysql_error()); echo("<script type='text/javascript'>"); echo("alert('MYSQL Database Selected.');"); echo("</script>"); //query $result = mysql_query("SELECT * FROM logins") or die(mysql_error()); //check results against given login while($row = mysql_fetch_array($result)){ if($row[login] == $value){ echo("true"); exit(0); } } echo("false"); exit(0); ?>) { login.setCustomValidity("Invalid Login. Please Click 'Register' Below.") } else { login.setCustomValidity("") } }); } the code is in an external js file and the error throws on the last line. Also from reading i understand best practices is to not mix js and php so how would i got about separating them but maintaining the functionality i need? thanks!

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• Serializability of enum-like class

  - by callisto

  I need to access an enum through a webservice. As a webservice allocates 0 based integers to an enumeration (ignoring preset values in enum definition), I built the following: public class StatusType { public StatusVal Pending { get { return new StatusVal( 1, "Pending"); } } public StatusVal Authorised { get { return new StatusVal(2, "Authorised"); } } public StatusVal Rejected { get { return new StatusVal(3, "Rejected"); } } public StatusVal Sent { get { return new StatusVal(4, "Sent"); } } public StatusVal InActive { get { return new StatusVal(5, "InActive"); } } public List<StatusVal> StatusList() { List<StatusVal> returnVal = new List<StatusVal>(); StatusType sv = new StatusType(); returnVal.Add(sv.Pending); returnVal.Add(sv.Authorised); returnVal.Add(sv.Rejected); returnVal.Add(sv.Sent); returnVal.Add(sv.InActive); return returnVal; } } public class StatusVal { public StatusVal(int a, string b) { this.ID = a; this.Name = b; } public int ID { get; set; } public string Name { get; set; } } I then get the list of StatusVal with the following webmethod: [WebMethod] public List<ATBusiness.StatusVal> GetStatus() { ATBusiness.StatusType a = new ATBusiness.StatusType(); return a.StatusList(); } I cannot however use this webmethod as referring it, I get the error: StatusVal cannot be serialized because it does not have a parameterless constructor. I don't quite understand: should I pass params into the StatusValue type defined as the WebMethod's return Type? I need this to return a list of StatusVals as per the StatusList() method.

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• Need help getting Wysihat to work

  - by slythic

  Hi all, I'm using Wysihat in a rails project and am stumped by it's inability to bind to my textarea named post_description (model name Post field name description). I have the following in my head tag: <%= javascript_include_tag 'prototype_1.7'%> <%= javascript_include_tag 'wysihat' %> <script type="text/javascript" charset="utf-8"> document.on("dom:loaded", function() { var editor = WysiHat.Editor.attach('post_description'); var toolbar = new WysiHat.Toolbar(editor); toolbar.addButtonSet(WysiHat.Toolbar.ButtonSets.Basic); // Hide our error message if the editor loads fine $('error').hide(); }); </script> I'm able to see Wysihat works (the bold, italic, and underline tools are shown and when click works as intended). The following in the source of the posts/new HTML: <div id="post_description_editor" class="editor" contenteditable="true"></div> <textarea cols="40" id="post_description" name="post[description]" rows="20" style="display: none; "></textarea> However, when I type something in the description field and click submit the post validation fails saying the description field is empty. Anyone have any clue on how I can get this to work? Thanks in advance!

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• User will input some filter criteria -- how can I turn it into a regular expression for String.match

  - by envinyater

  I have a program where the user will enter a string such as PropertyA = "abc_*" and I need to have the asterisk match any character. In my code, I'm grabbing the property value and replacing PropertyA with the actual value. For instance, it could be abc_123. I also pull out the equality symbol into a variable. It should be able to cover this type of criteria PropertyB = 'cba' PropertyC != '*-this' valueFromHeader is the lefthand side and value is the righthand side. if (equality.equals("=")) { result = valueFromHeader.matches(value); } else if (equality.equals("!=")) { result = !valueFromHeader.matches(value); } EDIT: The existing code had this type of replacement for regular expressions final String ESC = "\\$1"; final String NON_ALPHA = "([^A-Za-z0-9@])"; final String WILD = "*"; final String WILD_RE_TEMP = "@"; final String WILD_RE = ".*"; value = value.replace(WILD, WILD_RE_TEMP); value = value.replaceAll(NON_ALPHA,ESC); value = value.replace(WILD_RE_TEMP, WILD_RE); It doesn't like the underscore here... abcSite_123 != abcSite_123 (evaluates to true) abcSite_123$1.matches("abcSite$1123") It doesn't like the underscore...

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• Apache and linux file permissions can't browse file or directories

  - by dardub

  I just copied my magento site over to a local server running CentOS 5.4. The browser said it can't locate the location of the stylesheets. The stylesheets are within /skin/frontend/my_new_interface/design2/css. I tried to view in the browser and I can't view any of the files within the css directory. I verified a million times that I'm typing in the correct location. I can view files within /skin/frontend/my_new_interface/design2. Can't browse directories within browser however. I typed in ls -l css and get: -rwxr-xr-x 1 apache apache listed for all the files I tried chmod -R 755 and the directories I changed the apache conf Options Indexes But still when I browse the directories I get Forbidden. However, in another fresh installation of magento in the same www dir, I am able to browse directories. As far as I can tell both installations have same ownership and permissions. I also tried find . -type f -exec chmod 644 {} \; find . -type d -exec chmod 755 {} \; which was recommended in the magento wiki I've just run out of ideas.

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• threading in c#

  - by I__

  i am using this code: private void Form1_Load(object sender, EventArgs e) { } private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e) { string response = serialPort1.ReadLine(); this.BeginInvoke(new MethodInvoker( () => textBox1.AppendText(response + "\r\n") )); } ThreadStart myThreadDelegate = new ThreadStart(ThreadWork.DoWork); Thread myThread = new Thread(myThreadDelegate); myThread.Start(); but am getting lots of errors: Error 2 The type or namespace name 'ThreadStart' could not be found (are you missing a using directive or an assembly reference?) C:\Users\alexluvsdanielle\AppData\Local\Temporary Projects\WindowsFormsApplication1\Form1.cs 31 44 WindowsFormsApplication1 Error 3 The name 'ThreadWork' does not exist in the current context C:\Users\alexluvsdanielle\AppData\Local\Temporary Projects\WindowsFormsApplication1\Form1.cs 31 56 WindowsFormsApplication1 Error 4 The type or namespace name 'Thread' could not be found (are you missing a using directive or an assembly reference?) C:\Users\alexluvsdanielle\AppData\Local\Temporary Projects\WindowsFormsApplication1\Form1.cs 32 31 WindowsFormsApplication1 Error 5 A field initializer cannot reference the non-static field, method, or property 'WindowsFormsApplication1.Form1.myThreadDelegate' C:\Users\alexluvsdanielle\AppData\Local\Temporary Projects\WindowsFormsApplication1\Form1.cs 32 38 WindowsFormsApplication1 what am i doing wrong?

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• [java] Returning the element number of the longest string in an array

  - by JohnRoberts

  Hoookay, so. I'm trying to get the longestS method to take the user-inputted array of strings, then return the element number of the longest string in that array. I got it to the point where I was able to return the number of chars in the longest string, but I don't believe that will work for what I need. My problem is that I keep getting incompatible type errors when trying to figure this out. I don't understand the whole data type thing with strings yet. It's confusing me how I go about return a number of the array yet the array is of strings. The main method is fine, I got stuck on the ???? part. { public static void main(String [] args) { Scanner inp = new Scanner( System.in ); String [] responseArr= new String[4]; for (int i=0; i<4; i++) { System.out.println("Enter string "+(i+1)); responseArr[i] = inp.nextLine(); } int highest=longestS(responseArr); } public static int longestS(String[] values) { int largest=0 for( int i = 1; i < values.length; i++ ) { if ( ????? ) } return largest; } }

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• Surely a foolish error, but I can't see it

  - by dnagirl

  I have a form (greatly simplified): <form action='http://example.com/' method='post' name='event_form'> <input type='text' name='foo' value='3'/> <input type='submit' name='event_submit' value='Edit'/> </form> And I have a class "EventForm" to process the form. The main method, process() looks like this: public function process($submitname=false){ $success=false; if ($submitname && isset($_POST[$submitname])){ //PROBLEM: isset($_POST[$submitname] is always FALSE for some reason if($success=$this->ruler->validate()){//check that dependancies are honoured and data types are correct if($success=$this->map_fields()){//divide input data into Event, Schedule_Element and Temporal_Expression(s) $success=$this->eventholder->save(); } } } else {//get the record from the db based on event_id or schedule_element_id foreach($this->gets as $var){//list of acceptable $_GET keys if(isset($_GET[$var])){ if($success= $this->__set($var,$_GET[$var])) break; } } } $this->action=(empty($this->eventholder->event_id))? ADD : EDIT; return $success; } When the form is submitted, this happens: $form->process('event_submit'); For some reason though, isset($_POST['event_submit']) always evaluates to FALSE. Can anyone see why?

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• SPSS - sum of squares change radically with slight model changes in ANOVA??

  - by Pat

  I have noticed that the sum of squares in my models can change fairly radically with even the slightest adjustment to my models???? Is this normal???? I'm using SPSS 16, and both models presented below used the same data and variables with only one small change - categorizing one of the variables as either a 2 level or 3 level variable. Details - using a 2 x 2 x 6 mixed model ANOVA with the 6 being the repeated measure i get the following in the between group analysis ------------------------------------------------------------ Source | Type III SS | df | MS | F | Sig ------------------------------------------------------------ intercept | 4086.46 | 1 | 4086.46 | 104.93 | .000 X | 224.61 | 1 | 224.61 | 5.77 | .019 Y | 2.60 | 1 | 2.60 | .07 | .80 X by Y | 19.25 | 1 | 19.25 | .49 | .49 Error | 2570.40 | 66 | 38.95 | Then, when I use the exact same data but a slightly different model in which variable Y has 3 levels instead of 2 levels I get the following ------------------------------------------------------------ Source | Type III SS | df | MS | F | Sig ------------------------------------------------------------ intercept | 3603.88 | 1 | 3603.88 | 90.89 | .000 X | 171.89 | 1 | 171.89 | 4.34 | .041 Y | 19.23 | 2 | 9.62 | .24 | .79 X by Y | 17.90 | 2 | 17.90 | .80 | .80 Error | 2537.76 | 64 | 39.65 | I don't understand why variable X would have a different sum of squares simply because variable Y gets devided up into 3 levels instead of 2. This is also the case in the within groups analysis too. Please help me understand :D Thank you in advance Pat

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• cython setup.py gives .o instead of .dll

  - by alok1974

  Hi, I am a newbie to cython, so pardon me if I am missing something obvious here. I am trying to build c extensions to be used in python for enhanced performance. I have fc.py module with a bunch of function and trying to generate a .dll through cython using dsutils and running on win64: c:\python26\python c:\cythontest\setup.py build_ext --inplace I have the dsutils.cfg in C:\Python26\Lib\distutils. As required the disutils.cfg has the following config settings: [build] compiler = mingw32 My startup.py looks like this: from distutils.core import setup from distutils.extension import Extension from Cython.Distutils import build_ext ext_modules = [Extension('fc', [r'C:\cythonTest\fc.pyx'])] setup( name = 'FC Extensions', cmdclass = {'build_ext': build_ext}, ext_modules = ext_modules ) I have latest version mingw for target/host amdwin64 type builds. I have the latest version of cython for python26 for win64. Cython does give me an fc.c without errors, only a few warning for type conversions, which I will handle once I have it right. Further it produces fc.def an fc.o files Instead of giving a .dll. I get no errors. I find on threads that it will create the .so or .dll automatically as required, which is not happening.

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• Catch hibernate exceptions with errorpage handler?

  - by membersound

  I'm catching all exceptions within: java.lang.Throwable /page.xhtml java.lang.Error /page.xhtml But what If I get eg a hibernate ex: org.hibernate.exception.ConstraintViolationException Do I have to define error-pages for EVERY maybe occuring exception? Can't I just say "catch every exception"? Update Redirect on a 404 works. But on a throwable does not! <servlet> <servlet-name>Faces Servlet</servlet-name> <servlet-class>javax.faces.webapp.FacesServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>Faces Servlet</servlet-name> <url-pattern>*.jsf</url-pattern> <url-pattern>*.xhtml</url-pattern> </servlet-mapping> <error-page> <exception-type>java.lang.Throwable</exception-type> <location>/error.xhtml</location> </error-page> <error-page> <error-code>404</error-code> <location>/error.xhtml</location> </error-page>

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• friend declaration in C++

  - by Happy Mittal

  In Thinking in C++ by Bruce eckel, there is an example given regarding friend functions as // Declaration (incomplete type specification): struct X; struct Y { void f(X*); }; struct X { // Definition private: int i; public: friend void Y::f(X*); // Struct member friend }; void Y::f(X* x) { x->i = 47; } Now he explained this: Notice that Y::f(X*) takes the address of an X object. This is critical because the compiler always knows how to pass an address, which is of a fixed size regardless of the object being passed, even if it doesn’t have full information about the size of the type. If you try to pass the whole object, however, the compiler must see the entire structure definition of X, to know the size and how to pass it, before it allows you to declare a function such as Y::g(X). But when I tried void f(X); as declaration in struct Y, it shows no error. Please explain why?

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• OOP design issue: Polymorphism

  - by Graham Phillips

  I'm trying to solve a design issue using inheritance based polymorphism and dynamic binding. I have an abstract superclass and two subclasses. The superclass contains common behaviour. SubClassA and SubClassB define some different methods: SubClassA defines a method performTransform(), but SubClassB does not. So the following example 1 var v:SuperClass; 2 var b:SubClassB = new SubClassB(); 3 v = b; 4 v.performTransform(); would cause a compile error on line 4 as performTransform() is not defined in the superclass. We can get it to compile by casting... (v as SubClassA).performTransform(); however, this will cause a runtime exception to be thrown as v is actually an instance of SubClassB, which also does not define performTransform() So we can get around that by testing the type of an object before casting it: if( typeof v == SubClassA) { (cast v to SubClassA).performTransform(); } That will ensure that we only call performTransform() on v's that are instances of SubClassA. That's a pretty inelegant solution to my eyes, but at least its safe. I have used interface based polymorphism (interface meaning a type that can't be instantiated and defines the API of classes that implement it) in the past, but that also feels clunky. For the above case, if SubClassA and SubClassB implemented ISuperClass that defined performTransform, then they would both have to implement performTransform(). If SubClassB had no real need for a performTransform() you would have to implement an empty function. There must be a design pattern out there that addresses the issue.

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• What to call factory-like (java) methods used with immutable objects

  - by StaxMan

  When creating classes for "immutable objects" immutable meaning that state of instances can not be changed; all fields assigned in constructor) in Java (and similar languages), it is sometimes useful to still allow creation of modified instances. That is, using an instance as base, and creating a new instance that differs by just one property value; other values coming from the base instance. To give a simple example, one could have class like: public class Circle { final double x, y; // location final double radius; public Circle(double x, double y, double r) { this.x = x; this.y = y; this.r = r; } // method for creating a new instance, moved in x-axis by specified amount public Circle withOffset(double deltaX) { return new Circle(x+deltaX, y, radius); } } So: what should method "withOffset" be called? (note: NOT what its name ought to be -- but what is this class of methods called). Technically it is kind of a factory method, but somehow that does not seem quite right to me, since often factories are just given basic properties (and are either static methods, or are not members of the result type but factory type). So I am guessing there should be a better term for such methods. Since these methods can be used to implement "fluent interface", maybe they could be "fluent factory methods"? Better suggestions? EDIT: as suggested by one of answers, java.math.BigDecimal is a good example with its 'add', 'subtract' (etc) methods. Also: I noticed that there's this question (by Jon Skeet no less) that is sort of related (although it asks about specific name for method)

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• C++ Suppress Automatic Initialization and Destruction

  - by Travis G

  How does one suppress the automatic initialization and destruction of a type? While it is wonderful that T buffer[100] automatically initializes all the elements of buffer, and destroys them when they fall out of scope, this is not the behavior I want. #include <iostream> static int created = 0, destroyed = 0; struct S { S() { ++created; } ~S() { ++destroyed; } }; template <typename T, size_t KCount> class Array { private: T m_buffer[KCount]; public: Array() { // some way to suppress the automatic initialization of m_buffer } ~Array() { // some way to suppress the automatic destruction of m_buffer } }; int main() { { Array<S, 100> arr; } std::cout << "Created:\t" << created << std::endl; std::cout << "Destroyed:\t" << destroyed << std::endl; return 0; } The output of this program is: Created: 100 Destroyed: 100 I would like it to be: Created: 0 Destroyed: 0 My only idea is to make m_buffer some trivially constructed and destructed type like char and then rely on operator[] to wrap the pointer math for me, although this seems like a horribly hacked solution. Another solution would be to use malloc and free, but that gives a level of indirection that I do not want.

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• How do I prevent qFatal() from aborting the application?

  - by Dave

  My Qt application uses Q_ASSERT_X, which calls qFatal(), which (by default) aborts the application. That's great for the application, but I'd like to suppress that behavior when unit testing the application. (I'm using the Google Test Framework.) I have by unit tests in a separate project, statically linking to the class I'm testing. The documentation for qFatal() reads: Calls the message handler with the fatal message msg. If no message handler has been installed, the message is printed to stderr. Under Windows, the message is sent to the debugger. If you are using the default message handler this function will abort on Unix systems to create a core dump. On Windows, for debug builds, this function will report a _CRT_ERROR enabling you to connect a debugger to the application. ... To supress the output at runtime, install your own message handler with qInstallMsgHandler(). So here's my main.cpp file: #include <gtest/gtest.h> #include <QApplication> void testMessageOutput(QtMsgType type, const char *msg) { switch (type) { case QtDebugMsg: fprintf(stderr, "Debug: %s\n", msg); break; case QtWarningMsg: fprintf(stderr, "Warning: %s\n", msg); break; case QtCriticalMsg: fprintf(stderr, "Critical: %s\n", msg); break; case QtFatalMsg: fprintf(stderr, "My Fatal: %s\n", msg); break; } } int main(int argc, char **argv) { qInstallMsgHandler(testMessageOutput); testing::InitGoogleTest(&argc, argv); return RUN_ALL_TESTS(); } But my application is still stopping at the assert. I can tell that my custom handler is being called, because the output when running my tests is: My Fatal: ASSERT failure in MyClass::doSomething: "doSomething()", file myclass.cpp, line 21 The program has unexpectedly finished. What can I do so that my tests keep running even when an assert fails?

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