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  • How to implement arrays in an interpreter?

    - by Ray
    I have managed to write several interpreters including Tokenizing Parsing, including more complicated expressions such as ((x+y)*z)/2 Building bytecode from syntax trees Actual bytecode execution What I didn't manage: Implementation of dictionaries/lists/arrays. I always got stuck with getting multiple values into one variable. My value structure (used for all values passed around, including variables) looks like this, for example: class Value { public: ValueType type; int integerValue; string stringValue; } Works fine with integers and strings, but how could I implement arrays? (From now on with array I mean arrays in my experimental language, not in C++) How can I fit the array concept into the Value class above? Is it possible? How should I make arrays able to be passed around just as you could pass around integers and strings in my language, using the class above? Accessing array elements or memory allocation wouldn't be the problem, I just don't know how to store them.

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  • PHP MYSQL Endless Loop

    - by Neb
    Hi, I have a problem with my php/mysql script. It should only output the while loop once but I am getting unlimited loops and an endless page. $query = mysql_query("SELECT * FROM users WHERE username ='".base64_encode($_SESSION['username'])."' LIMIT 1"); $result = mysql_fetch_array($query); if(empty($result)){ echo "No user... Error"; }else{ while($row = $result){ ?> <a href="index.php?user=<?=$row['id']?>"><?=base64_decode($row['username'])?></a> | <a href="javascript:void(0);" id="logout">Logout</a> <?php } } I have tried a similar script with these same lines and it works perfectly $result = mysql_fetch_array($query); if(empty($result)){ echo "No user... Error"; }else{ while($row = $result){ //Something } }

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  • Consecutive 'if' statements

    - by Ben Packard
    How can I check one thing AND THEN another, if the first is true? For example, say I have a shopping basket object, and I only want to do something if the basket has been created AND it isn't empty. I've tried: if (basket && [basket numberOfItems >0])... But the second condition is evaluated even if the first fails, resulting in a crash (presumably because i'm calling numberOfItems on an object that doesn't exist). I can nest them, but this seems a bit ugly, and more to the point is problematic. Say I want to do one thing if the basket exists AND isn't empty, but another if either isn't true. That doesn't really work well in nested if statements.

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  • how to translate Haskell into Scalaz?

    - by TOB
    One of my high school students and I are going to try to do a port of Haskell's Parsec parser combinator library into Scala. (It has the advantage over Scala's built-in parsing library that you can pass state around fairly easily because all the parsers are monads.) The first hitch I've come across is trying to figure out how Functor works in scalaz. Can someone explain how to convert this Haskell code: data Reply s u a = Ok a !(State s u) ParseError | Error ParseError instance Functor (Reply s u) where fmap f (Ok x s e) = Ok (f x) s e fmap _ (Error e) = Error e -- XXX into Scala (using Scalaz, I assume). I got as far as sealed abstract class Reply[S, U, A] case class Ok[S, U, A](a: A, state: State[S, U], error: ParseError) extends Reply[S, U, A] case class Error[S, U, A](error: ParseError) extends Reply[S, U, A] and know that I should make Reply extend the scalaz.Functor trait, but I can't figure out how to do that. (Mostly I'm having trouble figuring out what the F[_] parameter does.) Any help appreciated! Thanks, Todd

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  • Storing year/make/model in a database?

    - by Mark
    Here's what I'm thinking (excuse the Django format): class VehicleMake(Model): name = CharField(max_length=50) class VehicleModel(Model): make = ForeignKey(VehicleMake) name = CharField(max_length=50) class VehicleYear(Model): model = ForeignKey(VehicleModel) year = PositiveIntegerField() This is going to be used in those contingent drop-down select boxes, which would visually be laid out like [- Year -][- Make -][- Model -]. So, to query the data I need I would first have to select all distinct years from the years table, sorted descending. Then I'd find all the vehicle makes that have produced a model in that year. And then all the models by that make in that year. Is this a good way to do it, or should I re-arrange the foreign keys somehow? Or use a many-to-many table for the years/models so that no year is repeated?

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  • How does git-diff generate hunk descriptions?

    - by RobM
    (git version 1.6.5.7) When I run git diff the output has a nice scope hint after the line numbers for my Python scripts, e.g.: diff --git a/file.py b/file.py index 024f5bb..c3b5c56 100644 --- a/file.py +++ b/file.py @@ -14,6 +14,8 @@ TITF: Test Infrastructure Tags Format ... @@ -1507,13 +1533,16 @@ class Tags( object ): ... Note that the line numbers are followed by TITF: Test Infrastructure Tags Format and class Tags( object ):. The first patch applies to module scope and the description TITF: Test Infrastructure Tags Format is the module's description. The second patch applies to a method of the Tags class. How does git generate these descriptions? How can I tweak them to show the method name that the patch applies to?

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  • Why should i use EJB?

    - by Nitesh Panchal
    Hello, As we all know that EJB's in 3.1 or 3.0 are simple POJOs. You just need to give annotations here and there and it gets converted to EJB from simple class. So, now my question is why should i use EJBs at all? Can i not do without them? In .Net i created class library and got things done. I never felt the need for anything like EJB. Simple classes were enough. Then, why in Java people stress on EJB? What is difference between a simple POJO and EJB in terms of execution and memory? Further which function should i write in EJB and which should i write in simple class? Should i dump every function in EJB only? or there is some kind of strategy? Does EJB provide anything special?

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  • With Eclipse, in a PHP project with SVN, how to "tell" Eclipse to find autocompletion choice only in

    - by ranskalainen
    Hello, Using Eclipse on a PHP Project, I recently created a tag on my SVN. Since that day, let's say I'm working on a class in my trunk, when I ctrl+space in my code, Eclipse is getting really really slow (sometimes even freeze), and if I'm lucky, it will give me 2 responses for autocompletion : One referencing some method/class from the tag, one referencing method/class from the trunk. But right now, only the reference from the trunk would be useful for me. Is there a way to limit where Eclipse parse the code to give back autocompletion suggestion ? Thank you

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  • Generic WithEvents

    - by serhio
    Error: 'WithEvents' variables can only be typed as classes, interfaces or type parameters with class constraints Background: Public Class Tadpole(Of T As IVisibleChanged, P As IVisibleChanged) Private WithEvents _Tad As T ' ERROR ' Private WithEvents _Pole As P ' ERROR ' Public Property Tad() As T ... Public Property Pole() As P ... End Class ''' IVisibleChanged ''' Public Interface IVisibleChanged Property Visible() As Boolean Event VisibleChanged As EventHandler End Interface Workaround: a. Use AddHandler to handle events defined in a structure. EDIT b. use Private WithEvents _Tad AsIVisibleChanged (M.A. Hanin) c. ?

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  • Custom login in Django

    - by alpgs
    Django newbie here. I wrote simplified login form which takes email and password. It works great if both email and password are supplied, but if either is missing i get KeyError exception. According to django documentation this should never happen: By default, each Field class assumes the value is required, so if you pass an empty value -- either None or the empty string ("") -- then clean() will raise a ValidationError exception I tried to write my own validators for fields (clean_email and clean_password), but it doesn't work (ie I get KeyError exception). What am I doing wrong? class LoginForm(forms.Form): email = forms.EmailField(label=_(u'Your email')) password = forms.CharField(widget=forms.PasswordInput, label=_(u'Password')) def clean_email(self): data = self.cleaned_data['email'] if not data: raise forms.ValidationError(_("Please enter email")) return data def clean_password(self): data = self.cleaned_data['password'] if not data: raise forms.ValidationError(_("Please enter your password")) return data def clean(self): try: username = User.objects.get(email__iexact=self.cleaned_data['email']).username except User.DoesNotExist: raise forms.ValidationError(_("No such email registered")) password = self.cleaned_data['password'] self.user = auth.authenticate(username=username, password=password) if self.user is None or not self.user.is_active: raise forms.ValidationError(_("Email or password is incorrect")) return self.cleaned_data

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  • Rails HABTM Scoping to current subdomain

    - by Rabbott
    I have the following associations: class User < ActiveRecord::Base has_and_belongs_to_many :brands, :join_table => 'brands_users' has_and_belongs_to_many :companies, :join_table => 'companies_users' end class Brand < ActiveRecord::Base belongs_to :company has_and_belongs_to_many :users, :join_table => 'brands_users' end class Company < ActiveRecord::Base has_and_belongs_to_many :users, :join_table => 'companies_users' has_many :brands, :order => :name end While editing a user I am using the checkbox list of brands. So that I can assign users 'access' to brands, the brands that show up are only the brands that belong to the current company (defined by the subdomain [using subdomain_fu]). The problem I am running into is that when using the default HABTM functionality and the checkbox list, upon save, Rails removes ALL user-brand associations, then re-adds just the ones for the form I just submitted.. How do I scope that to only remove associations of brands who belong to the current company, defined in the subdomain?

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  • Grouping a generic list via LINQ in VB.NET

    - by CD Smith
    I need to take a collection and group it via Linq but all the examples I've seen fail in some manner or other with some syntax difference that I can't quite lick. My collection: Dim a As New List(Of ProcessAlert) a.Add(New ProcessAlert("0000112367", "[email protected]", "Alert", 2)) a.Add(New ProcessAlert("0000112367", "[email protected]", "Document", 2)) a.Add(New ProcessAlert("0000112367", "[email protected]", "Note", 2)) a.Add(New ProcessAlert("0000112367", "[email protected]", "Alert", 1)) a.Add(New ProcessAlert("0000112367", "[email protected]", "Document", 1)) a.Add(New ProcessAlert("0000112367", "[email protected]", "Note", 1)) Return a I need to turn this collection into a simple way to give this final outcome: "[email protected]", "Alert, Document, Note" "[email protected]", "Alert, Document, Note" Here's the definition of the ProcessAlert class: Public Class ProcessAlert Public LoanNumber As String Public EmailAddress As String Public AlertType As String Public AlertMethodID As Byte End Class Thanks in advance, CD

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  • Simple Windows.Forms binding is failing using framework 4.0.

    - by jyoung
    This works under the .net framework 3.5 client. This fails under the .net framework 4.0 client. Was I doing something that was illegal under 3.5 but just happened to work, or is this a bug? Note that in my project 'PropInt' does not raise change events so using ctx[obj1.PropObj2, "PropInt"] is not an option. public class Obj1 { public Obj2 PropObj2 { get; set; } public Obj1() { PropObj2 = new Obj2(); } } public class Obj2 { public int PropInt { get; set; } } static class Program { [STAThread] static void Main() { var ctx = new BindingContext(); var obj1 = new Obj1(); var x1 = ctx[obj1, "PropObj2.PropInt"]; } }

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  • Silverlight 4 Assembly Sharing Problem

    - by jeffn825
    I have a WPF .NET 4.0 class library referencing a Silverlight 4 class library. The SL library compiles fine but when I compile the WPF class library, I get: Error 2 Unknown build error, 'Cannot resolve dependency to assembly 'System.Windows, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' because it has not been preloaded. When using the ReflectionOnly APIs, dependent assemblies must be pre-loaded or loaded on demand through the ReflectionOnlyAssemblyResolve event.' MyProj.Presentation.Wpf I figure the problem must be similar to the one mentioned here: http://markti.spaces.live.com/blog/cns!D92CF278F0F91957!273.entry but my WPF library doesn't contain any XAML that references a user control from my SL library. In fact, my SL library doesn't have any XAML in it at all. It does, however, have several shared DependencyObjects, such as an EventCommander (binding UI element events to Commands), and some DataTemplate helpers. Is there any way I can narrow down the problem here? And has anyone found a way of effectively referencing UI elements in a SL4 project from .NET 4.0? Thanks.

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  • Ruby Metaprogramming

    - by VP
    I'm trying to write a DSL that allows me to do Policy.name do author "Foo" reviewed_by "Bar" end The following code can almost process it: class Policy include Singleton def self.method_missing(name,&block) puts name puts "#{yield}" end def self.author(name) puts name end def self.reviewed_by(name) puts name end end Defining my method as class methods (self.method_name) i can access it using the following syntax: Policy.name do Policy.author "Foo" Policy.reviewed_by "Bar" end If i remove the "self" from the method names, and try to use my desired syntax, then i receive an error "Method not Found" in the Main so it could not find my function until the module Kernel. Its ok, i understand the error. But how can i fix it? How can i fix my class to make it work with my desired syntax that?

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  • android call an outside function from a thread

    - by junmats
    hi.. say for example I have this code in my activity: public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Thread cThread = new Thread(new Runner()); cThread.start(); } private NotifyMe(){ //do something here } and this is my Runner class: public class TCPClient implements Runnable { public void run(){ //call NotifyMe() [THIS IS MY QUESTION] } } I have a thread on my activity that runs the Runner Class. Once the thread start, I would like to call the NotifyMe() function that is located at the activity. Is this possible? Please let me know if you don't understand my question. Thanks in advance.

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  • Prepopulate drop-box according to another drop-box choice in Django Admin

    - by onorua
    I have models like this: class User(models.Model): Switch = models.ForeignKey(Switch, related_name='SwitchUsers') Port = models.ForeignKey(Port) class Switch(models.Model): Name = models.CharField(max_length=50) class Port(models.Model): PortNum = models.PositiveIntegerField() Switch = models.ForeignKey(Switch, related_name = "Ports") When I'm in Admin interface and choose Switch from Switches available, I would like to have Port prepopulated accordingly with Ports from the related Switch. As far as I understand I need to create some JS script to prepopulate it. Unfortunately I don't have this experience, and I would like to keep things simple as it possible and don't rewrite all Django admin interface. Just add this functionality for one Field. Could you please help me with my problem? Thank you.

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  • NSArray safeguards

    - by Spider-Paddy
    If there is a chance that an NSArray is empty, is it better to check it and set equal to nil if it's empty when it is assigned or to rather do the check when it is used? e.g. NSArray *myArray; if ([anotherArray count] > 0) <-- Check when assigned myArray = [anotherArray copy]; else myArray = nil; something = [myArray objectAtIndex:x]; or NSArray *myArray; myArray = [anotherArray copy]; if ([myArray count] > 0) <-- Check when used something = [myArray objectAtIndex:x]; Which is better?

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  • Why does the data binding in this validation example work?

    - by MartyIX
    I'm wondering how exactly the XAML sample (MSDN sample) works: <Style x:Key="textBoxInError" TargetType="{x:Type TextBox}"> <Style.Triggers> <Trigger Property="Validation.HasError" Value="true"> <Setter Property="ToolTip" Value="{Binding RelativeSource={x:Static RelativeSource.Self}, Path=(Validation.Errors)[0].ErrorContent}"/> </Trigger> </Style.Triggers> </Style> Questions: (Validation.Errors)[0].ErrorContent - Is this code somehow checked by WPF? Because Validation.Errors may be an empty collection and in ordinary C# code this code may throw an exception. If this data-binding returns null for valid input - the null value is then casted to empty string (in a text control for example)? The index 0 corresponds to the first error message. How can I return more error messages from Validate method? Thank you for responses!

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  • Django: Geocoding an address on form submission?

    - by User
    Trying to wrap my head around django forms and the django way of doing things. I want to create a basic web form that allows a user to input an address and have that address geocoded and saved to a database. I created a Location model: class Location(models.Model): address = models.CharField(max_length=200) city = models.CharField(max_length=100) state = models.CharField(max_length=100, null=True) postal_code = models.CharField(max_length=100, null=True) country = models.CharField(max_length=100) latitude = models.DecimalField(max_digits=18, decimal_places=10, null=True) longitude = models.DecimalField(max_digits=18, decimal_places=10, null=True) And defined a form: class LocationForm(forms.ModelForm): class Meta: model = models.Location exclude = ('latitude','longitude') In my view I'm using form.save() to save the form. This works and saves an address to the database. I created a module to geocode an address. I'm not sure what the django way of doing things is, but I guess in my view, before I save the form, I need to geocode the address and set the lat and long. How do I set the latitude and longitude before saving?

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  • Why is the C# SerializedAttribute is sealed?

    - by ahmet alp balkan
    I was trying to create an attribute that implies [Serializable] but I noticed that this SerializableAttribute class is sealed. In Java it was possible to create an interface (say, MyInterface) that is inherited from Serializable interface and so all the subclasses of MyInterface would also be serializable, even its sub-sub classes would be so. Let's say I am creating an ORM and I want customers to annotate their entity classes as [DatabaseEntity] but in order to make sure that entities are serializable, I also need to ask them to attribute their classes with extra [Serializable] which does not look quite compact and neat. I am wondering why SerializableAttribute class is sealed and why has Inherited=false which implies that subclasses of serializable class will not be serializable unless it is explicitly stated. What motives are behind these design choices?

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  • Java: Non-static nested classes and instance.super()

    - by Kiv
    I'm having a hard time wrapping my head around non-static nested classes in Java. Consider the following example, which prints "Inner" and then "Child". class Outer { class Inner { Inner() { System.out.println("Inner"); } } } public class Child extends Outer.Inner { Child(Outer o) { o.super(); System.out.println("Child"); } public static void main(String args[]) { new Child(new Outer()); } } I understand that instances of Inner always have to be associated with an Outer instance, and that that applies to Child too since it extends Inner. My question is what the o.super() syntax means - why does it call the Inner constructor? I've only seen a plain super(args) used to call the superclass constructor and super.method() to call the superclass version of an overridden method, but never something of the form instance.super().

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  • Flags with border on hover

    - by Alpan67
    Hello I have 3 flags (Italian, german, english) with the purpose to change language for the whole site in future. How can I make a border on a hover effect that could alxo work with IE ? this is the CCS .miniflags { float:right margin : 5px 20px; padding-right:10px; } and here the HTML <div id="bandiere"> <a><img src="ita.png" class="miniflags" /></a> <a><img src="ger.png" class="miniflags" /></a> <a><img src="eng.png" class="miniflags" /></a> </div> Thanx for help Alex

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  • ADT will not allow creation of Android Activity

    - by NewShelbyWoo
    I installed the ADT bundle from http://developer.android.com/sdk/index.html yesterday, and I was following a basic Hello World tutorial. I created a new Android Application Project with a Blank Activity named MainActivity. The resulting project has an empty src folder and empty res\layout folder. There is a R.java file in the gen folder but it has no reference to MainActivity. This is what the SDK manager says I have installed Android SDK Tools v 22.6 Android SDK Platform-tools v 19.0.1 Android SDK Build-tools v 19 SDK Platform v 3 ARM EABI v7a System Image v 2 Android Support Library v 19.0.1 Google USB Driver v 9 I also tried manually creating an activity by right clicking the src folder and going to Android Activity, but when I hit Finish on the creation wizard, nothing happens. Does anyone have any clues as to what's going on? Did I miss a key component to install or something?

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  • Dynamically creating page definitions in Cherrypy

    - by Hugh
    Hi, I've been looking around the CherryPy documentation, but can't quite get my head around what I want to do. I suspect it might be more of a Python thing than a CherryPy thing... My current class looks something like this: import managerUtils class WebManager: def A(self, **kwds): return managerUtils.runAction("A", kwds) A.enabled = True def B(self, **kwds): return managerUtils.runAction("B", kwds) B.enabled = True def C(self, **kwds): return managerUtils.runAction("C", kwds) C.enabled = True Obviously there's a lot of repetition in here. in managerUtils.py, I have a dict that's something like: actions = {'A': functionToRunForA, 'B': functionToRunForB, 'C': functionToRunForC} Okay, so that's a slightly simplistic view of it, but I'm sure you get the idea. I want to be able to do something like: import managerUtils class WebManager: def __init__(self): for action in managerUtils.actions: f = registerFunction(action) f.enabled = True Any ideas of how to do this?

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