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  • Is a string formatter that pulls variables from its calling scope bad practice?

    - by Eric
    I have some code that does an awful lot of string formatting, Often, I end up with code along the lines of: "...".format(x=x, y=y, z=z, foo=foo, ...) Where I'm trying to interpolate a large number of variables into a large string. Is there a good reason not to write a function like this that uses the inspect module to find variables to interpolate? import inspect def interpolate(s): return s.format(**inspect.currentframe().f_back.f_locals) def generateTheString(x): y = foo(x) z = x + y # more calculations go here return interpolate("{x}, {y}, {z}")

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  • Temporary Tables in Stored Procedures

    - by Paul White
    Ask anyone what the primary advantage of temporary tables over table variables is, and the chances are they will say that temporary tables support statistics and table variables do not. This is true, of course; even the indexes that enforce PRIMARY KEY and UNIQUE constraints on table variables do not have populated statistics associated with them, and it is not possible to manually create statistics or non-constraint indexes on table variables. Intuitively, then, any query that has alternative execution...(read more)

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  • How can I share variables between a base class and subclass in Perl?

    - by Jonathan
    I have a base class like this: package MyClass; use vars qw/$ME list of vars/; use Exporter; @ISA = qw/Exporter/; @EXPORT_OK = qw/ many variables & functions/; %EXPORT_TAGS = (all => \@EXPORT_OK ); sub my_method { } sub other_methods etc { } --- more code--- I want to subclass MyClass, but only for one method. package MySubclass; use MyClass; use vars qw/@ISA/; @ISA = 'MyClass'; sub my_method { --- new method } And I want to call this MySubclass like I would the original MyClass, and still have access to all of the variables and functions from Exporter. However I am having problems getting the Exporter variables from the original class, MyClass, to export correctly. Do I need to run Exporter again inside the subclass? That seems redundant and unclear. Example file: #!/usr/bin/perl use MySubclass /$ME/; -- rest of code But I get compile errors when I try to import the $ME variable. Any suggestions?

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  • What are the drawbacks of using PHP to create variables in my CSS stylesheet?

    - by Greg
    One significant drawback of CSS is that one can't use variables. For example, I'd like to use variables to control the location of imported CSS, and it would be awesome to create variables for colors that are used repeatedly in a design. One approach is to use a PHP file for the CSS stylesheet. In other words, create a "style.php" with... <?php header("Content-type: text/css"); ?> ...at the top of the file, and then link to it using... <link href="style.php" rel="stylesheet" type="text/css" /> ...in any file that uses these styles. So what's the catch? I think it might be performance -- I did a few quick experiments in Firefox/Firebug and as one would expect, the CSS stylesheet is cached, but the PHP stylesheet isn't. So we're paying the price of an additional GET. The other annoying thing is that TextMate does not syntax highlight properly for CSS in a .php file. Are there other drawbacks? Have you used this approach, and if so, would you recommend it?

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  • Wait on multiple condition variables on Linux without unnecessary sleeps?

    - by Joseph Garvin
    I'm writing a latency sensitive app that in effect wants to wait on multiple condition variables at once. I've read before of several ways to get this functionality on Linux (apparently this is builtin on Windows), but none of them seem suitable for my app. The methods I know of are: Have one thread wait on each of the condition variables you want to wait on, which when woken will signal a single condition variable which you wait on instead. Cycling through multiple condition variables with a timed wait. Writing dummy bytes to files or pipes instead, and polling on those. #1 & #2 are unsuitable because they cause unnecessary sleeping. With #1, you have to wait for the dummy thread to wake up, then signal the real thread, then for the real thread to wake up, instead of the real thread just waking up to begin with -- the extra scheduler quantum spent on this actually matters for my app, and I'd prefer not to have to use a full fledged RTOS. #2 is even worse, you potentially spend N * timeout time asleep, or your timeout will be 0 in which case you never sleep (endlessly burning CPU and starving other threads is also bad). For #3, pipes are problematic because if the thread being 'signaled' is busy or even crashes (I'm in fact dealing with separate process rather than threads -- the mutexes and conditions would be stored in shared memory), then the writing thread will be stuck because the pipe's buffer will be full, as will any other clients. Files are problematic because you'd be growing it endlessly the longer the app ran. Is there a better way to do this? Curious for answers appropriate for Solaris as well.

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  • Java - How to declare table[i][j] elements as instance variables?

    - by JDelage
    All, I am trying to code a Connect4 game. For this, I have created a P4Game class and a P4Board class which represents the i X j dimensions of the Connect4 board. In P4Game, I have the following: public class P4Game{ //INSTANCE VARIABLES private int nbLines; private int nbColumns; private P4Board [][] position; //CONSTRUCTOR public P4Game(int nbLines, int nbColumns){ this.nbColumns = nbColumns; this.nbLines = nbLines; P4Board [][] position = new P4Board [nbLines][nbColumns]; //Creates the table to receive the instances of the P4Board object.*/ for (int i=0; i<nbLines; i++){ for (int j=0; j<nbColumns; j++){ this.position[i][j] = new P4Board(i,j); //Meant to create each object at (line=i, column=j) } } } This causes a NullPointerException in the nested loops where I mention this.position[i][j]. I reference those objects in other methods of this class so I need them to be instance variables. I suppose the exception is due to the fact that I have not listed the table element position[i][j] as an instance variable at the beginning of the class. my question to people here is (1) is my assumption correct, and if so (2) what would be the syntax to declare instance variables of this form? Thank you all for your help with what I realize is a very basic question. Hopefully it will also benefit other newbies. Cheers, JDelage

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  • is using private shared objects/variables on class level harmful ?

    - by haansi
    Hello, Thanks for your attention and time. I need your opinion on an basic architectural issue please. In page behind classes I am using a private and shared object and variables (list or just client or simplay int id) to temporary hold data coming from database or class library. This object is used temporarily to catch data and than to return, pass to some function or binding a control. 1st: Can this approach harm any way ? I couldn't analyze it but a thought was using such shared variables may replace data in it when multiple users may be sending request at a time? 2nd: Please comment also on using such variables in BLL (to hold data coming from DAL/database). In this example every time new object of BLL class will be made. Here is sample code: public class ClientManager { Client objclient = new Client(); //Used in 1st and 2nd method List<Client> clientlist = new List<Client>();// used in 3rd and 4th method ClientRepository objclientRep = new ClientRepository(); public List<Client> GetClients() { return clientlist = objclientRep.GetClients(); } public List<Client> SearchClients(string Keyword) { return clientlist = objclientRep.SearchClients(Keyword); } public Client GetaClient(int ClientId) { return objclient = objclientRep.GetaClient(ClientId); } public Client GetClientDetailForConfirmOrder(int UserId) { return objclientRep.GetClientDetailForConfirmOrder(UserId); } } I am really thankful to you for sparing time and paying kind attention.

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  • What does it mean to say "Instance variables are not over-rided" in java?

    - by Ankit
    I am aware of the concept called field hiding in java. But still I am having a confusion in relation to instance variable being not over-ridden. According to my present knowledge, overriding a method of super-class means that the JVM will call the sub-class's over-ridden method though the super-class's method is available to the sub-class. And I read the similar thing for field hiding via the link:- Hiding Fields So, in any case we are over-ridding the instance if we change the values of the inherited instance variable in the sub-class. I am confused please help. I am using the following super-class:- public class Animal{ File picture; String food; int hunger; int width, height; int xcoord, ycoord; public void makeNoise(){ ......... } public void eat(){ ............. } public void sleep(){ .......... } public void roam(){ ............. } } It has sub-classes like Tiger, cat, dog,hippo etc. The sub-classes over-ride the makeNoise(), eat and roam() method. But each sub-class also uses a different set of values for instance variables. So as per my confusion, I am kind-of overriding all the instance variables and 3 methods of the super-class Animal; and I still have the super-class instance variables available to the sub-class with the use of the super keyword.

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  • How can I create global context variables in JBOSS?

    - by NobodyMan
    This is a follow-up to a question I posted a while back: "Can I use a single WAR in multiple environments?". I was able to create a single-war solution in Tomcat, but now we are migrating our app to JBoss 4.2 and I can't figure out how to set up global environment variables. In Tomcat 6 this was pretty straightforward: I simply put the following snippet in tomcat/conf/Catalina/myappname.xml: <Context ...> <Environment name="TARGET_ENV" value="DEV" type="java.lang.String" override="false"/> </Context> Then in my app I was able to resolve the environment name with the following: Context context = (Context) InitialContext().lookup("java:comp/env"); String targetEnvironment = (String) context.lookup("TARGET_ENV"); The problem is that I can't find out where/how to place global variables in JBoss. I've tried putting the <Environment> tag in the following files to no avail: server/all/deploy/jboss-web.deployer/context.xml server/default/deploy/jboss-web.deployer/context.xml I know that I can put environment variables in my app's web.xml but that defeats the purpose of having a unified war - I'd still need custom .war's for dev, qa and prod. I'm a JBoss newbie so if there's any additional information that would help just let me know and I'll append to this question. Many thanks! --N

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  • When should we use private variables and when should we use properties.

    - by Shantanu Gupta
    In most of the cases we usually creates a private variable and its corresponding public properties and uses them for performing our functionalities. Everyone has different approach like some ppl uses properties every where and some uses private variables within a same class as they are private and opens it to be used by external environment by using properties. Suppose I takes a scenario say insertion in a database. I creates some parameters that need to be initialized. I creates 10 private variables and their corresp public properties which are given as private string name; public string Name { get{return name;} set{name=value;} } and so on. In these cases what should be used internally variables or properties. And in those cases like public string Name { get{return name;} set{name=value>5?5:0;} //or any action can be done. this is just an eg. } In such cases what should be done.

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  • Why aren't variables declared in "try" in scope in "catch" or "finally"?

    - by Jon Schneider
    In C# and in Java (and possibly other languages as well), variables declared in a "try" block are not in scope in the corresponding "catch" or "finally" blocks. For example, the following code does not compile: try { String s = "test"; // (more code...) } catch { Console.Out.WriteLine(s); //Java fans: think "System.out.println" here instead } In this code, a compile-time error occurs on the reference to s in the catch block, because s is only in scope in the try block. (In Java, the compile error is "s cannot be resolved"; in C#, it's "The name 's' does not exist in the current context".) The general solution to this issue seems to be to instead declare variables just before the try block, instead of within the try block: String s; try { s = "test"; // (more code...) } catch { Console.Out.WriteLine(s); //Java fans: think "System.out.println" here instead } However, at least to me, (1) this feels like a clunky solution, and (2) it results in the variables having a larger scope than the programmer intended (the entire remainder of the method, instead of only in the context of the try-catch-finally). My question is, what were/are the rationale(s) behind this language design decision (in Java, in C#, and/or in any other applicable languages)?

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  • When should we use private variables and when should we use properties. Do Backing Fields should be

    - by Shantanu Gupta
    In most of the cases we usually creates a private variable and its corresponding public properties and uses them for performing our functionalities. Everyone has different approach like some people uses properties every where and some uses private variables within a same class as they are private and opens it to be used by external environment by using properties. Suppose I takes a scenario say insertion in a database. I creates some parameters that need to be initialized. I creates 10 private variables and their corresp public properties which are given as private string name; public string Name { get{return name;} set{name=value;} } and so on. In these cases mentioned above, what should be used internal variables or properties. And in those cases like public string Name { get{return name;} set{name=value>5?5:0;} //or any action can be done. this is just an eg. } In such cases what should be done.

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  • ASP.NET MVC 2.0 Unused Model Property being called when posting a product to the server?

    - by Erx_VB.NExT.Coder
    i have my auto-generated linq to sql classes, and i extend this class using partial classing (instead of using inheritance), and i have properties that that i've put in later which are not part of the database model and should not be. these are things like "FinalPrice" and "DisplayFinalPrice" - in the dbase, there is only RetailPrice and WholesalePrice so FinalPrice etc are more like extensions of the dbase fields. when i submit the form with nothing filled in, "FinalPrice" gets called (the 'get' of the property) even tho i never ask for it to be, and even tho it is not needed. this happens before validation, so i don't even get the validation errors i would get. i've tried using and on the FinalPrice and FinalPriceDisplay properties - no go! why does this happen and how can i stop it from happening? is the modelstate just trying to validate everything so therefore it calls every item no matter what? for those interested, here is all the code... Partial Public Class tProduct 'Inherits tProduct Private Const CommissionMultiplier As Decimal = CDec(1.18) Private _FinalPrice As Decimal? Private _DisplayFinalPrice As String Private _DisplayNormalPrice As String Public Property CategoryComplete As Short <ScaffoldColumn(False)> Public ReadOnly Property FinalPrice As Decimal Get 'If RetailPrice IsNot Nothing OrElse WholesalePrice IsNot Nothing Then If _FinalPrice Is Nothing Then If RetailPrice IsNot Nothing Then _FinalPrice = RetailPrice Else _FinalPrice = WholesalePrice * CommissionMultiplier ' TODO: this should be rounded to the nearest 5th cent so prices don't look weird. End If Dim NormalPart = Decimal.Floor(_FinalPrice.Value) Dim DecimalPart = _FinalPrice.Value - NormalPart If DecimalPart = 0 OrElse DecimalPart = 0.5 Then Return _FinalPrice ElseIf DecimalPart > 0 AndAlso DecimalPart < 0.5 Then DecimalPart = 0.5 ' always rounded up to the nearest 50 cents. ElseIf DecimalPart > 0.5 AndAlso DecimalPart < 1 Then ' Only in this case round down if its about to be rounded up to a valeu like 20, 30 or 50 etc as we want most prices to end in 9. If NormalPart.ToString.LastChr.ToInt = 9 Then DecimalPart = 0.5 Else DecimalPart = 1 End If End If _FinalPrice = NormalPart + DecimalPart End If Return _FinalPrice 'End If End Get End Property <ScaffoldColumn(False)> Public ReadOnly Property DisplayFinalPrice As String Get If _DisplayFinalPrice.IsNullOrEmpty Then _DisplayFinalPrice = FormatCurrency(FinalPrice, 2, TriState.True) End If Return _DisplayFinalPrice End Get End Property Public ReadOnly Property DisplayNormalPrice As String Get If _DisplayNormalPrice.IsNullOrEmpty Then _DisplayNormalPrice = FormatCurrency(NormalPrice, 2, TriState.True) End If Return _DisplayNormalPrice End Get End Property Public ReadOnly Property DivID As String Get Return "pdiv" & ProductID End Get End Property End Class more... i get busted here, with a null reference exception telling me it should contain a value... Dim NormalPart = Decimal.Floor(_FinalPrice.Value)

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  • Should old/legacy/unused code be deleted from source control repository?

    - by Checkers
    I've encountered this in multiple projects. As the code base evolves, some libraries, applications, and components get abandoned and/or deprecated. Most people prefer to keep them in. The usual argument is that the code does not really take any space, it can be left alone until needed again. So a repository slowly turns into a cesspool of legacy code, where it's hard to find anything. Some people delete old code, since it creates clutter, raises more questions for new people, and you can restore any old snapshot of the code base anyway. However you can't always find the old code if you don't know where to look, as none of the (common) VCS I know offer search over the entire repository including all historical revisions, and the only way to search the old files is to check out the revision where the deleted file exists. What would be a good approach to repository management?

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  • Can I detect unused extra parameters passed to javascript methods?

    - by Pablojim
    In Javascript I can call any method with more than the necessary amount of parameters and the extra parameters are silently ignored. e.g. letters = ['a','b','c'] //correct letters.indexOf('a') //This also works without error or warning letters.indexOf('a', "blah", "ignore me", 38) Are there ways to detect cases where this occurs? My motivation is that in my experience cases where this occurs are usually bugs. Identification of these by code analysis or at runtime would help track these errors down. These cases are especially prevalent where people are expecting alterations to base types which may not have occurred. Logging a warning where this happens e.g. Date.parse('02--12--2012', 'dd--MM--YYYY') Notes: To be clear I would like a solution that doesn't involve me sprinkling checks all over my code and other peoples' code.

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  • Can a conforming C# compiler optimize away a local (but unused) variable if it is the only strong re

    - by stakx
    The title says it all, but let me explain: void Case_1() { var weakRef = new WeakReference(new object()); GC.Collect(); // <-- doesn't have to be an explicit call; just assume that // garbage collection would occur at this point. if (weakRef.IsAlive) ... } In this code example, I obviously have to plan for the possibility that the new'ed object is reclaimed by the garbage collector; therefore the if statement. (Note that I'm using weakRef for the sole purpose of checking if the new'ed object is still around.) void Case_2() { var unusedLocalVar = new object(); var weakRef = new WeakReference(unusedLocalVar); GC.Collect(); // <-- doesn't have to be an explicit call; just assume that // garbage collection would occur at this point. Debug.Assert(weakReferenceToUseless.IsAlive); } The main change in this code example from the previous one is that the new'ed object is strongly referenced by a local variable (unusedLocalVar). However, this variable is never used again after the weak reference (weakRef) has been created. Question: Is a conforming C# compiler allowed to optimize the first two lines of Case_2 into those of Case_1 if it sees that unusedLocalVar is only used in one place, namely as an argument to the WeakReference constructor? i.e. is there any possibility that the assertion in Case_2 could ever fail?

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  • Delphi: Which are the downsides of having unused units listed in the uses clause?

    - by user193655
    I use cnPack Uses cleaner, but in general which are the downsides of having useless units? I know some of them: 1) of course if the unit is never used across the full project there will be useless resource consuption 2) the code insight will give useless results 3) the code insight will be slower But imagine a simple case: I have a project with 2 forms, I use StrUtils in one of them but I declared StrUtils in both of them... Is there any downside in temrs of memory consumption in this case or not?

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  • How to access variables in an erb-subtemplate in puppet?

    - by c33s
    example.pp $foo = 'bar' $content = template('mymodule/maintemplate.erb') maintemplate.erb <% bar = foo + "extra" %> foobar = scope_function_template(['mymodule/subtemplate.erb']) subtemplate.erb <%# here i want to access the variable bar %> <%= bar %> there is the function <%= scope.lookupvar('::bar') %> is there a kind of parent::bar in erb templateing, or can i pass some variables to the subtemplate, or can i only access the outer variable (of the .pp file) with ::foo

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  • Is there a snippets program that allows for tab entry of variables across the mac?

    - by Jeremy Smith
    I love Sublime Text editor and the ability to create code snippets like so: <snippet> <content><![CDATA[\$("${1:selector}").${2:method}]]></content> <tabTrigger>jq</tabTrigger> </snippet> This allows me to type jq[tab] and then have it expand to $("selector").method where I am able to tab through the string 'selector' and 'method' in order to change them. But what I'd really like to do is use this same snippet when working in Chrome Dev Tools, so I was looking for a mac snippets program that could support this. However, the three programs that I looked at (Keyboard Maestro, Snippets, CodeBox) don't support the ability to tab through to highlight predetermined strings and change them. Does anyone know of an app that will do this?

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