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• Sending variables in URLs in PHP with echo

  - by alexpelan

  Hi all, I can't really find good guidelines through google searches of the proper way to escape variables in URLs. Basically I am printing out a bunch of results from a mysql query in a table and I want one of the entries in each row to be a link to that result's page. I think this is easy, that I'm just missing a apostrophe or backslash somewhere, but I can't figure it out. Here's the line that's causing the error: echo "<a href = \"movies.php/?movie_id='$row['movie_id']'\"> Who Owns It? </a> "; and this is the error I'm getting: Parse error: syntax error, unexpected T_ENCAPSED_AND_WHITESPACE, expecting T_STRING or T_VARIABLE or T_NUM_STRING If you could elaborate in your answers about general guidelines for working with echo and variables in urls, that would be great. Thanks.

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• question about class derivation in c++?

  - by jack22

  hi, i want to know some things about class derivation in c++ so i have super class x and an inherited class y and i did this class x{ public:a; private:b; protected:c; } class y:public x{ public:d; } in this case how y can access a,b,and c and by how i mean(public,protected,private) the second case: class x{ public:a; private:b; protected:c; } class y:private x{ public:d; } the same question? the third case: class x{ public:a; private:b; protected:c; } class y:private x{ public:d; } again the same question? sorry i think i wrote too much bye

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• how can we call one class's method through another class's object in php

  - by hello

  I want to know that is there any method in PHP by which i can call one class's method from another class object. let me clear here is one class class A() { public function showData(){ //here is method of class A } } // here is another class class B(){ public function getData(){ //some method in class B } } //now i create two objects $objA= new class A(); $objB=new class B(); now i want to call this $objB->showData();<--- is that possible .. by any how method( using public, inheritence,child parent etc...) please help me

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• Printing out variables in c changes values of variables

  - by George Wilson

  I have an odd problem with some c-programme here. I was getting some wrong values in a matrix I was finding the determinant of and so I started printing variables - yet found that by printing values out the actual values in the code changed. I eventually narrowed it down to one specific printf statement - highlighted in the code below. If I comment out this line then I start getting incorrect values in my determinent calculations, yet by printing it out I get the value out I expect Code below: #include <math.h> #include <stdio.h> #include <stdlib.h> #define NUMBER 15 double determinant_calculation(int size, double array[NUMBER][NUMBER]); int main() { double array[NUMBER][NUMBER], determinant_value; int size; array[0][0]=1; array[0][1]=2; array[0][2]=3; array[1][0]=4; array[1][1]=5; array[1][2]=6; array[2][0]=7; array[2][1]=8; array[2][2]=10; size=3; determinant_value=determinant_calculation(size, array); printf("\n\n\n\n\n\nDeterminant value is %lf \n\n\n\n\n\n", determinant_value); return 0; } double determinant_calculation(int size, double array[NUMBER][NUMBER]) { double determinant_matrix[NUMBER][NUMBER], determinant_value; int x, y, count=0, sign=1, i, j; /*initialises the array*/ for (i=0; i<(NUMBER); i++) { for(j=0; j<(NUMBER); j++) { determinant_matrix[i][j]=0; } } /*does the re-cursion method*/ for (count=0; count<size; count++) { x=0; y=0; for (i=0; i<size; i++) { for(j=0; j<size; j++) { if (i!=0&&j!=count) { determinant_matrix[x][y]=array[i][j]; if (y<(size-2)) { y++; } else { y=0; x++; } } } } //commenting this for loop out changes the values of the code determinent prints -7 when commented out and -3 (expected) when included! for (i=0; i<size; i++) { for(j=0; j<size; j++){ printf("%lf ", determinant_matrix[i][j]); } printf("\n"); } if(size>2) { determinant_value+=sign*(array[0][count]*determinant_calculation(size-1 ,determinant_matrix)); } else { determinant_value+=sign*(array[0][count]*determinant_matrix[0][0]); } sign=-1*sign; } return (determinant_value); } I know its not the prettiest (or best way) of doing what I'm doing with this code but it's what I've been given - so can't make huge changes. I don't suppose anyone could explain why printing out the variables can actually change the values? or how to fix it because ideally i don't want to!!

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• Accessing XAML Object Variables in XAML

  - by Asryael

  So, what I'm trying to do is access my Form's width and/or height to use in a storyboard. Essentially, I have a Translate Transform animation to slide what are essentially two pages. The animation works fine with hard coded From/To variables, however I need to use soft variables that enable the animation to start from the left/right of my form no matter what size it is. <Storyboard x:Key="SlideLeftToRight" TargetProperty="RenderTransform.(TranslateTransform.X)" AccelerationRatio=".4" DecelerationRatio=".4"> <DoubleAnimation Storyboard.TargetName="PageViewer" Duration="0:0:0.6" From="WindowWidth" To="0"/> <DoubleAnimation Storyboard.TargetName="BorderVisual" Duration="0:0:0.6" From="0" To="NegativeWindowWidth"/> </Storyboard> However, I have no idea how to do so. Any help is greatly appreciated. EDIT: I'm guessing it has something to do with: From="{Binding Width, Source=MainWindow}" However, when I attempt this, I don't know how to make it negative.

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• In game programming are global variables bad?

  - by Joe.F

  I know my gut reaction to global variables is "badd!" but in the two game development courses I've taken at my college globals were used extensively, and now in the DirectX 9 game programming tutorial I am using (www.directxtutorial.com) I'm being told globals are okay in game programming ...? The site also recommends using only structs if you can when doing game programming to help keep things simple. I'm really confused on this issue, and all the research I've been trying to do is very confusing. I realize there are issues when using global variables (threading issues, they make code harder to maintain, the state of them is hard to track etc) but also there is a cost associated with not using globals, I'd have to pass a loooot of information around very often which can be confusing and I imagine time-costing, although I guess pointers would speed the process up (this is my first time writing a game in C++.) Anyway, I realize there is probably no "right" or "wrong" answer here since both ways work, but I want my code to be as proper as I can so any input would be good, thank you very much!

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• Generate a List of All Variables used in a Visual Studio Project

  - by Jammie

  Is it possible to generate a list of all the variables used in a visual studio project?

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• JQuery: loop through elements with more than one css class name that share only the first class name

  - by omaether

  Hello, I'm trying to use JQuery to loop through several div's with more than one class name, that all have the same first css class name and each one has a different second class name, e.g. <div class="maintext blue"> </div> <div class="maintext purple"> </div> <div class="maintext chartreuse"> </div> <div class="maintext puce"> </div> <div class="maintext lime"> </div> In JQuery I have tried $(".mainText").each(function (i) $(".mainText.*").each(function (i) $(".mainText" *).each(function (i) $(".mainText .*").each(function (i) But it will not select any of the divs with class="mainText ..." thanks for considering the question.

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• Give a reference to a python instance attribute at class definition

  - by Guenther Jehle

  I have a class with attributes which have a reference to another attribute of this class. See class Device, value1 and value2 holding a reference to interface: class Interface(object): def __init__(self): self.port=None class Value(object): def __init__(self, interface, name): self.interface=interface self.name=name def get(self): return "Getting Value \"%s\" with interface \"%s\""%(self.name, self.interface.port) class Device(object): interface=Interface() value1=Value(interface, name="value1") value2=Value(interface, name="value2") def __init__(self, port): self.interface.port=port if __name__=="__main__": d1=Device("Foo") print d1.value1.get() # >>> Getting Value "value1" with interface "Foo" d2=Device("Bar") print d2.value1.get() # >>> Getting Value "value1" with interface "Bar" print d1.value1.get() # >>> Getting Value "value1" with interface "Bar" The last print is wrong, cause d1 should have the interface "Foo". I know whats going wrong: The line interface=Interface() line is executed, when the class definition is parsed (once). So every Device class has the same instance of interface. I could change the Device class to: class Device(object): interface=Interface() value1=Value(interface, name="value1") value2=Value(interface, name="value2") def __init__(self, port): self.interface=Interface() self.interface.port=port So this is also not working: The values still have the reference to the original interface instance and the self.interface is just another instance... The output now is: >>> Getting Value "value1" with interface "None" >>> Getting Value "value1" with interface "None" >>> Getting Value "value1" with interface "None" So how could I solve this the pythonic way? I could setup a function in the Device class to look for attributes with type Value and reassign them the new interface. Isn't this a common problem with a typical solution for it? Thanks!

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• Which is the better C# class design for dealing with read+write versus readonly

  - by DanM

  I'm contemplating two different class designs for handling a situation where some repositories are read-only while others are read-write. (I don't foresee any need to a write-only repository.) Class Design 1 -- provide all functionality in a base class, then expose applicable functionality publicly in sub classes public abstract class RepositoryBase { protected virtual void SelectBase() { // implementation... } protected virtual void InsertBase() { // implementation... } protected virtual void UpdateBase() { // implementation... } protected virtual void DeleteBase() { // implementation... } } public class ReadOnlyRepository : RepositoryBase { public void Select() { SelectBase(); } } public class ReadWriteRepository : RepositoryBase { public void Select() { SelectBase(); } public void Insert() { InsertBase(); } public void Update() { UpdateBase(); } public void Delete() { DeleteBase(); } } Class Design 2 - read-write class inherits from read-only class public class ReadOnlyRepository { public void Select() { // implementation... } } public class ReadWriteRepository : ReadOnlyRepository { public void Insert() { // implementation... } public void Update() { // implementation... } public void Delete() { // implementation... } } Is one of these designs clearly stronger than the other? If so, which one and why? P.S. If this sounds like a homework question, it's not, but feel free to use it as one if you want :)

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• Request for advice about class design, inheritance/aggregation

  - by Lasse V. Karlsen

  I have started writing my own WebDAV server class in .NET, and the first class I'm starting with is a WebDAVListener class, modelled after how the HttpListener class works. Since I don't want to reimplement the core http protocol handling, I will use HttpListener for all its worth, and thus I have a question. What would the suggested way be to handle this: Implement all the methods and properties found inside HttpListener, just changing the class types where it matters (ie. the GetContext + EndGetContext methods would return a different class for WebDAV contexts), and storing and using a HttpListener object internally Construct WebDAVListener by passing it a HttpListener class to use? Create a wrapper for HttpListener with an interface, and constrct WebDAVListener by passing it an object implementing this interface? If going the route of passing a HttpListener (disguised or otherwise) to the WebDAVListener, would you expose the underlying listener object through a property, or would you expect the program that used the class to keep a reference to the underlying HttpListener? Also, in this case, would you expose some of the methods of HttpListener through the WebDAVListener, like Start and Stop, or would you again expect the program that used it to keep the HttpListener reference around for all those things? My initial reaction tells me that I want a combination. For one thing, I would like my WebDAVListener class to look like a complete implementation, hiding the fact that there is a HttpListener object beneath it. On the other hand, I would like to build unit-tests without actually spinning up a networked server, so some kind of mocking ability would be nice to have as well, which suggests I would like the interface-wrapper way. One way I could solve this would be this: public WebDAVListener() : WebDAVListener(new HttpListenerWrapper()) { } public WebDAVListener(IHttpListenerWrapper listener) { } And then I would implement all the methods of HttpListener (at least all those that makes sense) in my own class, by mostly just chaining the call to the underlying HttpListener object. What do you think? Final question: If I go the way of the interface, assuming the interface maps 1-to-1 onto the HttpListener class, and written just to add support for mocking, is such an interface called a wrapper or an adapter?

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• C++: Retriving values of static const variables at a constructor of a static variable

  - by gilbertc

  I understand that the code below would result segmentation fault because at the cstr of A, B::SYMBOL was not initialized yet. But why? In reality, A is an object that serves as a map that maps the SYMBOLs of classes like B to their respective IDs. C holds this map(A) static-ly such that it can provide the mapping as a class function. The primary function of A is to serve as a map for C that initializes itself at startup. How should I be able to do that without segmentation fault, provided that I can still use B::ID and B::SYMBOL in the code (no #define pls)? Thanks! Gil. class A { public: A() { std::cout<<B::ID<<std::endl; std::cout<<B::SYMBOL<<std::endl; } }; class B { public: static const int ID; static const std::string SYMBOL; } const int B::ID = 1; const std::string B::SYMBOL = "B"; class C { public: static A s_A; }; A C::s_A; int main(int c, char** p) { }

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• Adding Variables to JavaScript in Joomla

  - by Vikram

  Hello friends! This is the script I am using to display an accordion in my Joomla site: <?php defined('JPATH_BASE') or die(); gantry_import('core.gantryfeature'); class GantryFeatureAccordion extends GantryFeature { var $_feature_name = 'accordion'; function init() { global $gantry; if ($this->get('enabled')) { $gantry->addScript('accordion.js'); $gantry->addInlineScript($this->_accordion()); } } function render($position="") { ob_start(); ?> <div id="accordion"> <dl> <?php foreach (glob("templates/rt_gantry_j15/features/accordion/*.php") as $filename) {include($filename);} ?> </dl> </div> <?php return ob_get_clean(); } function _accordion() { global $gantry; $js = " jQuery.noConflict(); (function($){ $(document).ready(function () { $('#accordion').easyAccordion({ slideNum: true, autoStart: true, slideInterval: 4000 }); }); })(jQuery); "; return $js; } } I want to call these three values in the templateDetails.XML file as a user input. slideNum: true, autoStart: true, slideInterval: 4000 Like this in the templateDetails.xml file: <param name="accordion" type="chain" label="ACCORDION" description="ACCORDION_DESC"> <param name="slideNum" type="text" default="true" label="Offset Y" class="text-short" /> <param name="autoStart" type="text" default="true" label="Offset Y" class="text-short" /> <param name="autoStart" type="text" default="4000" label="Offset Y" class="text-short" /> </param> How can I do so? What will be the exact syntax for the same. I am very new to programming ans specially to JavaScript. Kindly help.

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• Get information from a higher class?

  - by Clint Davis

  I don't know really how to word the question so please bear with me... I have 3 classes: Server, Database, and Table. Each class has a "Name" property. How I want it to work is that each server can have multiple databases and each database can have multiple tables. So in the Server class I have this property. Private _databases As List(Of Database) Public Property Databases() As List(Of Database) Get Return _databases End Get Set(ByVal value As List(Of Database)) _databases = value End Set End Property And I have something similar in the Database class for the tables. This works fine now because I can do something like this to get all the databases in the server. For Each db In s.Databases 's being the server object Debug.Print(db.Name) Next I would like to expand these classes. I want the server class to handle all the connection information and I would like the other classes to use the server class's connection information in them. For example, I setup a server class and set the connection string to the server. Then I want the database class to use serverclass.connectionstring property to connect to the server and get a list of all the databases. But I want to keep that code in the database class. How can I do this? I've attached some code of what I want to do. Public Class Server Private _name As String Public Property Name() As String Get Return _name End Get Set(ByVal value As String) _name = value End Set End Property Private _databases As List(Of Database) Public Property Databases() As List(Of Database) Get Return _databases End Get Set(ByVal value As List(Of Database)) _databases = value End Set End Property End Class '-----New class Public Class Database Private _name As String Public Property Name() As String Get Return _name End Get Set(ByVal value As String) _name = value End Set End Property Private _tables As List(Of Table) Public Property Tables() As List(Of Table) Get Return _tables End Get Set(ByVal value As List(Of Table)) _tables = value End Set End Property 'This is where I need help! Private Sub LoadTables () dim connectionstring as string = server.connectionstring 'Possible? 'Do database stuff End Class Thanks for reading!

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• Is it legal to extend the Class class?

  - by spiralganglion

  I've been writing a system that generates some templates, and then generates some objects based on those templates. I had the idea that the templates could be extensions of the Class class, but that resulted in some magnificent errors: VerifyError: Error #1107: The ABC data is corrupt, attempt to read out of bounds. What I'm wondering is if subclassing Class is even possible, if there is perhaps some case where doing this would be appropriate, and not just a gross misuse of OOP. I believe it should be possible, as ActionScript allows you to create variables of the Class type. This use is described in the LiveDocs entry for Class, yet I've seen no mentions of subclassing Class. Here's a pseudocode example: class Foo extends Class var a:Foo = new Foo(); trace(a is Class) // true, right? var b = new a(); I have no idea what the type of b would be. In summary: can you subclass the Class class? If so, how can you do it without errors, and what type are the instances of the instances of the Class subclass?

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• Function returning a class containing a function returning a class

  - by Scott

  I'm working on an object-oriented Excel add-in to retrieve information from our ERP system's database. Here is an example of a function call: itemDescription = Macola.Item("12345").Description Macola is an instance of a class which takes care of database access. Item() is a function of the Macola class which returns an instance of an ItemMaster class. Description() is a function of the ItemMaster class. This is all working correctly. Items can be be stored in more than one location, so my next step is to do this: quantityOnHand = Macola.Item("12345").Location("A1").QuantityOnHand Location() is a function of the ItemMaster class which returns an instance of the ItemLocation class (well, in theory anyway). QuantityOnHand() is a function of the ItemLocation class. But for some reason, the ItemLocation class is not even being intialized. Public Function Location(inventoryLocation As String) As ItemLocation Set Location = New ItemLocation Location.Item = item_no Location.Code = inventoryLocation End Function In the above sample, the variable item_no is a member variable of the ItemMaster class. Oddly enough, I can successfully instantiate the ItemLocation class outside of the ItemMaster class in a non-class module. Dim test As New ItemLocation test.Item = "12345" test.Code = "A1" quantityOnHand = test.QuantityOnHand Is there some way to make this work the way I want? I'm trying to keep the API as simple as possible. So that it only takes one line of code to retrieve a value.

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• store in a variable only the first or only the second class of an element

  - by shecky

  I'm using this bit of jQ to add a class to two different elements based on the class of another (parent/grandparent, etc) element: $(document).ready(function(){ var containerClass = $('#main-content').attr('class'); $('#nav-primary li#'+containerClass).addClass('active'); $('#aux-left div[id$='+containerClass+']').addClass('active'); }); Brilliant, but I have two problems with it: First, when there's no class at all in <div id="main-content">, the 'active' class is added to all the #nav-primary LIs, and also to all the #aux-left DIVs; how can I modify this so that in the absence of any class on #main-content, do nothing? Second, how can I target only the first or second of multiple classes to store in the 'containerClass' variable, e.g., <div id="main-content" class="apples bananas">? Very much appreciated! svs

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• Python Class Variables Question

  - by zyq524

  I have some doubt about python's class variables. As my understanding, if I define a class variable, which is declared outside the init() function, this variable will create only once as a static variable in C++. This seems right for some python types, for instance, dict and list type, but for those base type, e.g. int,float, is not the same. For example: class A: dict1={} list1=list() int1=3 def add_stuff(self, k, v): self.dict1[k]=v self.list1.append(k) self.int1=k def print_stuff(self): print self.dict1,self.list1,self.int1 a1 = A() a1.add_stuff(1, 2) a1.print_stuff() a2=A() a2.print_stuff() The output is: {1: 2} [1] 1 {1: 2} [1] 3 I understand the results of dict1 and list1, but why does int1 behavior different?

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• design a model for a system of dependent variables

  - by dbaseman

  I'm dealing with a modeling system (financial) that has dozens of variables. Some of the variables are independent, and function as inputs to the system; most of them are calculated from other variables (independent and calculated) in the system. What I'm looking for is a clean, elegant way to: define the function of each dependent variable in the system trigger a re-calculation, whenever a variable changes, of the variables that depend on it A naive way to do this would be to write a single class that implements INotifyPropertyChanged, and uses a massive case statement that lists out all the variable names x1, x2, ... xn on which others depend, and, whenever a variable xi changes, triggers a recalculation of each of that variable's dependencies. I feel that this naive approach is flawed, and that there must be a cleaner way. I started down the path of defining a CalculationManager<TModel> class, which would be used (in a simple example) something like as follows: public class Model : INotifyPropertyChanged { private CalculationManager<Model> _calculationManager = new CalculationManager<Model>(); // each setter triggers a "PropertyChanged" event public double? Height { get; set; } public double? Weight { get; set; } public double? BMI { get; set; } public Model() { _calculationManager.DefineDependency<double?>( forProperty: model => model.BMI, usingCalculation: (height, weight) => weight / Math.Pow(height, 2), withInputs: model => model.Height, model.Weight); } // INotifyPropertyChanged implementation here } I won't reproduce CalculationManager<TModel> here, but the basic idea is that it sets up a dependency map, listens for PropertyChanged events, and updates dependent properties as needed. I still feel that I'm missing something major here, and that this isn't the right approach: the (mis)use of INotifyPropertyChanged seems to me like a code smell the withInputs parameter is defined as params Expression<Func<TModel, T>>[] args, which means that the argument list of usingCalculation is not checked at compile time the argument list (weight, height) is redundantly defined in both usingCalculation and withInputs I am sure that this kind of system of dependent variables must be common in computational mathematics, physics, finance, and other fields. Does someone know of an established set of ideas that deal with what I'm grasping at here? Would this be a suitable application for a functional language like F#? Edit More context: The model currently exists in an Excel spreadsheet, and is being migrated to a C# application. It is run on-demand, and the variables can be modified by the user from the application's UI. Its purpose is to retrieve variables that the business is interested in, given current inputs from the markets, and model parameters set by the business.

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• iphone global variables accessed from different views

  - by Rob

  Okay, so ultimately I want a program where the user can input simple data such as their name, date of birth, address, etc. and then have that information stay through multiple views. I am having the user input their information as UITextFields but their are multiple views that they are using to input the data. Is there a way that when the user inputs data in a UITextField - then moves to another view - then returns to the original view - that the data will still be in that UITextField? I figure since there are placeholders that there must be a command to show previously written text in that field when the viewController is called. Also, for the life of me, I can't figure out how to keep these variables global. I have read in multiple areas that I should define them in the AppDelegate as a simple: NSString *userName; NSString *userDOB; But how do I assign the strings from the UITextFields in a different view to these variables and then re-assign them to the UITextFields when the user returns to the place where they originally input them? (I apologize if I am not explaining this coherently - I am a bit of a newb)

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• Sharing runtime variables between files

  - by nightcracker

  I have a project with a few files that all include the header global.hpp. Those files want to share and update information that is relevant for the whole program during runtime (that data is gathered progressively during the program runs but the fields of data are known at compile-time). Now my idea was to use a struct like this: global.hpp #include <string> #ifndef _GLOBAL_SESSION_STRUCT #define _GLOBAL_SESSION_STRUCT struct session_struct { std::string username; std::string password; std::string hostname; unsigned short port; // more data fields as needed }; #endif extern struct session_struct session; main.cpp #include "global.hpp" struct session_struct session; int main(int argc, char* argv[]) { session.username = "user"; session.password = "secret"; session.hostname = "example.com"; session.port = 80; // other stuff, etc return 0; } Now every file that includes global.hpp can just read & write the fields of the session struct and easily share information. Is this the correct way to do this? NOTE: For this specific project no threading is used. But please (for future projects and other people reading) clarify in your answer how this (or your proposed) solution works when threaded. Also, for this example/project session variables are shared. But this should also apply to any other form of shared variables.

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• php request variables assigning $_GEt

  - by chris

  if you take a look at a previous question http://stackoverflow.com/questions/2690742/mod-rewrite-title-slugs-and-htaccess I am using the solution that Col. Shrapnel proposed- but when i assign values to $_GET in the actual file and not from a request the code doesnt work. It defaults away from the file as if the $_GET variables are not set The code I have come up with is- if(!empty($_GET['cat'])){ $_GET['target'] = "category"; if(isset($_GET['page'])){ $_GET['pageID'] = $_GET['page']; } $URL_query = "SELECT category_id FROM cats WHERE slug = '".$_GET['cat']."';"; $URL_result = mysql_query($URL_query); $URL_array = mysql_fetch_array($URL_result); $_GET['category_id'] = $URL_array['category_id']; }elseif($_GET['product']){ $_GET['target'] = "product"; $URL_query = "SELECT product_id FROM products WHERE slug = '".$_GET['product']."';"; $URL_result = mysql_query($URL_query); $URL_array = mysql_fetch_array($URL_result); print_r($URL_array); $_GET['product_id'] = $URL_array['product_id']; The original variable string that im trying to represent is /cart.php?Target=product&product_id=16142&category_id=249 And i'm trying to build the query string variables with code and including cart.php so i can use cleaner URL's So I have product/product-title-with-clean-url/ going to slug.php?product=slug Then the slug searches the db for a record with the matching slug and returns the product_id as in the code above.Then built the query string and include cart.php

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• C: Global ,Static variables understanding

  - by pavun_cool

  Hi All, In following program . I have one doubt. I have declared one global variable . I am printing the address of the global variable in the function . It is giving me same address when I am not changing the value of global . If I did any changes in the global variables It is giving me different address why...........? Like that it is happening for static also. #include<stdio.h> int global=10 ; // Global variables void function(); main() { global=20; printf ( " %p \n" , global ) ; printf ( " Val: %d\n", global ) ; function(); new(); } void function() { global=30; printf ( " %p \n" , global ) ; printf ( " Val: %d\n", global ) ; } Thanks.

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• Prolog singleton variables in Python

  - by Rubens

  I'm working on a little set of scripts in python, and I came to this: line = "a b c d e f g" a, b, c, d, e, f, g = line.split() I'm quite aware of the fact that these are decisions taken during implementation, but shouldn't (or does) python offer something like: _, _, var_needed, _, _, another_var_needed, _ = line.split() as well as Prolog does offer, in order to exclude the famous singleton variables. I'm not sure, but wouldn't it avoid unnecessary allocation? Or creating references to the result of the split call does not count up as overhead? EDIT: Sorry, my point here is: in Prolog, as far as I'm concerned, in an expression like: test(L, N) :- test(L, 0, N). test([], N, N). test([_|T], M, N) :- V is M + 1, test(T, V, N). The variable represented by _ is not accessible, for what I suppose the reference to the value that does exist in the list [_|T] is not even created. But, in Python, if I use _, I can use the last value assigned to _, and also, I do suppose the assignment occurs for each of the variables _ -- which may be considered an overhead. My question here is if shouldn't there be (or if there is) a syntax to avoid such unnecessary attributions.

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• MYSQL variables - SET @var

  - by Lizard

  I am attempting to create a mysql snippet that will analyse a table and remove duplicate entries (duplicates are based on two fields not entire record) I have the following code that works when I hard code the variables in the queries, but when I take them out and put them as variables I get mysql errors, below is the script SET @tblname = 'mytable'; SET @fieldname = 'myfield'; SET @concat1 = 'checkfield1'; SET @concat2 = 'checkfield2'; ALTER TABLE @tblname ADD `tmpcheck` VARCHAR( 255 ) NOT NULL; UPDATE @tblname SET `tmpcheck` = CONCAT(@concat1,'-',@concat2); CREATE TEMPORARY TABLE `tmp_table` ( `tmpfield` VARCHAR( 100 ) NOT NULL ) ENGINE = MYISAM ; INSERT INTO `tmp_table` (`tmpfield`) SELECT @fieldname FROM @tblname GROUP BY `tmpcheck` HAVING ( COUNT(`tmpcheck`) > 1 ); DELETE FROM @tblname WHERE @fieldname IN (SELECT `tmpfield` FROM `tmp_table`); ALTER TABLE @tblname DROP `tmpcheck`; I am getting the following error: #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '@tblname ADD `tmpcheck` VARCHAR( 255 ) NOT NULL' at line 1 Is this because I can't use a variable for a table name? What else could be wrong or how wopuld I get around this issue. Thanks in adavnce

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