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  • Single-letter prefix for PHP class constants?

    - by keithjgrant
    I've noticed many (all?) PHP constants have a single-letter prefix, like E_NOTICE, T_STRING, etc. When defining a set of class constants that work in conjunction with one another, do you prefer to follow similar practice, or do you prefer to be more verbose? class Foo { // let's say 'I' means "input" or some other relevant word const I_STRING = 'string'; const I_INTEGER = 'integer'; const I_FLOAT = 'float'; } or class Bar { const INPUT_STRING = 'string'; const INPUT_INTEGER = 'integer'; const INPUT_FLOAT = 'float'; }

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  • Integrating a Custom Compiler with the Visual Studio IDE

    - by M.A. Hanin
    Background: I want to create a custom VB compiler, extending the "original" compiler, to handle my custom compile-time attributes. Question: after I've created my custom compiler and I've got an executable file capable of compiling VB code via the standard command-line interface, how do I integrate this compiler with the Visual Studio IDE? (such that pressing "compile" or "build" will make use of my compiler instead of the default compiler). EDIT: (Correct me if i'm wrong) From the reactions here, I see this question is a bit shocking, so I shall further explain my needs and background: .NET provides us with a great mechanism called Attributes. As far as I understand, making attributes apply their intended behavior upon the attributed element (assembly, module, class, method, etc.) - attributes must be reflected upon. So the real trick here is reflecting and applying behavior at the right spot. Lets take Serialization for example: We decorate a class with the Serializable attribute. We then pass an instance of the class to the formatter's Serialize method. The formatter reflects upon the instance, checking if it has the Serializable attribute, and acting accordingly. Now, if we examine the Synchronization, Flags, Obsolete and CLSCompliant attributes, then the real question is: who reflects upon them? At least in some cases, it has to be the compiler (and/or IDE). Therefore, it seems that if I wish to create custom attributes that change an element's behavior regardless of any specific consumer, i must extend the compiler to reflect upon them at compilation. Of course, these are not my personal insights: the book "Applied .NET Attributes" provides a complete example of creating a custom attribute and a custom C# compiler to reflect upon that attribute at compilation (the example is used to implement "java-style checked exceptions").

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  • IDEA modular problem (jsp)

    - by Jeriho
    I have project in with 2 separate modules(frontend and backend, first depends on second). When I'm trying to access backend code from frontend code, things going fine. Things turn for the worse when I do the same from jsp. This is stacktrase for simple accessign bean <jsp:useBean id="mybean" class="backend.main.MyBean" scope="request"></jsp:useBean> org.apache.jasper.JasperException: /results.jsp(9,0) The value for the useBean class attribute backend.main.MyBean is invalid. org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:40) org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:407) org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:148) org.apache.jasper.compiler.Generator$GenerateVisitor.visit(Generator.java:1220) org.apache.jasper.compiler.Node$UseBean.accept(Node.java:1178) org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2361) org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2411) org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2417) org.apache.jasper.compiler.Node$Root.accept(Node.java:495) org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2361) org.apache.jasper.compiler.Generator.generate(Generator.java:3416) org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:231) org.apache.jasper.compiler.Compiler.compile(Compiler.java:347) org.apache.jasper.compiler.Compiler.compile(Compiler.java:327) org.apache.jasper.compiler.Compiler.compile(Compiler.java:314) org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:589) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:317) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260) javax.servlet.http.HttpServlet.service(HttpServlet.java:717) And this error will appear if I try to access regular class: An error occurred at line: 12 in the jsp file: /results.jsp backend.main.RegularClass cannot be resolved to a type Stacktrace: org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:92) org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:330) org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:439) org.apache.jasper.compiler.Compiler.compile(Compiler.java:349) org.apache.jasper.compiler.Compiler.compile(Compiler.java:327) org.apache.jasper.compiler.Compiler.compile(Compiler.java:314) org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:589) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:317) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260) javax.servlet.http.HttpServlet.service(HttpServlet.java:717) Sorry for so many stacktraces.

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  • Is Google Closure a true compiler?

    - by James Allardice
    This question is inspired by the debate in the comments on this Stack Overflow question. The Google Closure Compiler documentation states the following (emphasis added): The Closure Compiler is a tool for making JavaScript download and run faster. It is a true compiler for JavaScript. Instead of compiling from a source language to machine code, it compiles from JavaScript to better JavaScript. However, Wikipedia gives the following definition of a "compiler": A compiler is a computer program (or set of programs) that transforms source code written in a programming language (the source language) into another computer language... A language rewriter is usually a program that translates the form of expressions without a change of language. Based on that, I would say that Google Closure is not a compiler. But the fact that Google explicitly state that it is in fact a "true compiler" makes me wonder if there's more to it. Is Google Closure really a JavaScript compiler?

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  • Javascript: Machine Constants Applicable?

    - by DavidB2013
    I write numerical routines for students of science and engineering (although they are freely available for use by anybody else as well) and am wondering how to properly use machine constants in a JavaScript program, or if they are even applicable. For example, say I am writing a program in C++ that numerically computes the roots of the following equation: exp(-0.7x) + sin(3x) - 1.2x + 0.3546 = 0 A root-finding routine should be able to compute roots to within the machine epsilon. In C++, this value is specified by the language: DBL_EPSILON. C++ also specifies the smallest and largest values that can be held by a float or double variable. However, how does this convert to JavaScript? Since a Javascript program runs in a web browser, and I don't know what kind of computer will run the program, and JavaScript does not have corresponding predefined values for these quantities, how can I implement my own version of these constants so that my programs compute results to as much accuracy as allowed on the computer running the web browser? My first draft is to simply copy over the literal constants from C++: FLT_MIN: 1.17549435082229e-038 FLT_MAX: 3.40282346638529e+038 DBL_EPSILON: 2.2204460492503131e-16 I am also willing to write small code blocks that could compute these values for each machine on which the program is run. That way, a supercomputer might compute results to a higher accuracy than an old, low-level, PC. BUT, I don't know if such a routine would actually reach the computer, in which case, I would be wasting my time. Anybody here know how to compute and use (in Javascript) values that correspond to machine constants in a compiled language? Is it worth my time to write small programs in Javascript that compute DBL_EPSILON, FLT_MIN, FLT_MIN, etc. for use in numerical routines? Or am I better off simply assigning literal constants that come straight from C++ on a standard Windows PC?

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  • Where should I define constants in scripts?

    - by bshacklett
    When writing scripts using a modern scripting language, e.g. Powershell or JavaScript, where should I define constants? Should I make all constants global for readability and ease of use, or does it make sense to define constants as close to their scopes as possible (in a function, for instance, if it's not needed elsewhere)? I'm thinking mostly of error messages, error IDs, paths to resources or configuration options.

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  • Delphi Typed Constants in Case Statements

    - by Andreas Rejbrand
    What is the most elegant (or least ugly) way of using typed constants in a case statement in Delphi? That is, assume for this question that you need to declare a typed constant as in const MY_CONST: cardinal = $12345678; ... Then the Delphi compiler will not accept case MyExpression of MY_CONST: { Do Something }; ... end; but you need to write case MyExpression of $12345678: { Do Something }; ... end; which is error-prone, hard to update, and not elegant. Is there any trick you can employ to make the compiler insert the value of the constant (preferably by checking the value of the constant under const in the source code, but maybe by looking-up the value at runtime)? We assume here that you will not alter the value of the "constant" at runtime.

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  • C++ initializing constants and inheritance

    - by pingvinus
    I want to initialize constant in child-class, instead of base class. And use it to get rid of dynamic memory allocation (I know array sizes already, and there will be a few child-classes with different constants). So I try: class A { public: const int x; A() : x(0) {} A(int x) : x(x) {} void f() { double y[this->x]; } }; class B : A { B() : A(2) {} }; Pretty simple, but compiler says: error C2057: expected constant expression How can I say to compiler, that it is really a constant?

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  • What is the use of interface constants?

    - by kunjaan
    I am learning Java and just found that the Interface can have fields, which are public static and final. I haven't seen any examples of these so far. What are some of the use cases of these Interface Constants and can I see some in the Java Standard Library?

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  • Js constants with variables inside.

    - by johnnyArt
    I know I'm able to this in PHP, but I can't remember the name or the way to do it, so I'll just explain what it is, and when someone tells me how it's called I'll update this question. I have some error messages defined as constants on javascript, however, some of those messages need to contain dynamic part as in the following example. "The username must be between 4 and 20 characters" In php, If I'm not mistaken there was some option for storing that string in a way that when called it would replace the variables with the data provided on the call. I want to do that on javascript, something like: config['string',vars] And have javascript insert those vars inside the string so it's customized. Wow, this must be the worst question I've made! I'm sorry for the lack of information, I'm kinda braindead on Sundays.

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  • The Benefits of Constants

    - by onaclov2000
    I understand one of the big deals about constants is that you don't have to go through and update code where that constant is used all over the place. Thats great, but let's say you don't explicitly declare it as a constant. What benefit(s) exist(s) to take a variable that HAPPENS to actually not be changed and make it a constant, will this save on processing, and/or size of code...etc? Basically I have a program that the compiler is saying that a particular variable is not changed and thus can be declared a constant, I just wanted to know what the benefit to adding the constant qualifier to it would be, if it makes no difference then making that change adds no value and thus no point wasting time (this same scenario occurs in more then one place) going back and "fixing" all these variables. Thank you, onaclov

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  • How best to implement publicly accessible constants in C#

    - by DanM
    There seem to be three choices for implementing publicly accessible constants in C#. I'm curious if there are any good reason to choose one over the other or if it's just a matter of personal preference. Choice 1 - private field plus property getter private const string _someConstant = "string that will never change"; public string SomeConstant { get { return _someConstant; } } Choice 2 - property getter only public string SomeConstant { get { return "string that will never change"; } } Choice 3 - public field only public const string SomeConstant = "string that will never change"; Which do you recommend and why?

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  • modifying constants in objective c during run time

    - by moshikafya
    I am trying to solve the following problem. I have the following constants in my header file: #define PREFS_MY_CONSTANT_1 @"bla1" #define PREFS_MY_CONSTANT_2 @"bla2" #define PREFS_MY_CONSTANT_3 @"bla3" ... In one of my functions, I'd like to print to the UIbutton one of those strings based on user input, so say the user inputs '1', i would show bla1. Instead of creating a huge switch (i have 100 of those), I am looking for a way to combine the constant with the variable holding the user input, so something like that ideally: NSInteger input; [button setTitle:PREFS_MY_CONSTANT_{$input} forState: UIControlStateNormal]; Is something like that possible? what would be the best way to solve this?

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  • GWT - problems with constants in css

    - by hba
    Hi, I'm new to GWT; I'm building a small sample app. I have several CSS files. I'm able to successfully use the ClientBundle and CssResource to assign styles to the elements defined in my UiBinder script. Now I'd like to take it one step further and introduce CSS constants using @def css-rule. The @def works great when I define a constant and use it in the same CSS file. However I cannot use it in another CSS file. When I try to use the @eval rule to evaluate an existing constant the compiler throws an execption: "cannot make a static reference to the non-static method ". Here is an example of what I'm trying to do: ConstantStyle.css @def BACKGROUND red; ConstantStyle.java package abc; import ...; interface ConstantStyle extends cssResource { String BACKGROUND(); } MyStyle.css @eval BACKGROUND abc.ConstantStyle.BACKGROUND(); .myClass {background-color: BACKGROUND;} MyStyle.java package abc; import ...; interface ConstantStyle extends cssResource { String myClass; } MyResources.java package abc; import ...; interface MyResources extends ClientBundle { @Source("ConstantStyle.css") ConstantStyle constantStyle(); @Source("MyStyle.css") MyStyle myStyle(); } Thanks in advance!

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  • Automatically find compiler options for fastest exe on given machine?

    - by dehmann
    Is there a method to automatically find the best compiler options (on a given machine), which result in the fastest possible executable? Naturally, I use g++ -O3, but there are additional flags that may make the code run faster, e.g. -ffast-math and others, some of which are hardware-dependent. Does anyone know some code I can put in my configure.ac file (GNU autotools), so that the flags will be added to the Makefile automatically by the ./configure command? In addition to automatically determining the best flags, I would be interested in some useful compiler flags that are good to use as a default for most optimized executables.

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  • What does a JIT compiler do?

    - by mehmet6parmak
    Hi all, I was just watching the google IO videos and they talked about the JIT compiler they included in the android and showed a demo about performance improvements thanks to JIT compiler. I wondered what does exactly a JIT compiler do and wanted to hear from different people. So, What is the duty of a JIT compiler? Thanks all

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  • compiler warning at C++ template base class

    - by eike
    I get a compiler warning, that I don't understand in that context, when I compile the "Child.cpp" from the following code. (Don't wonder: I stripped off my class declarations to the bare minuum, so the content will not make much sense, but you will see the problem quicker). I get the warning with VS2003 and VS2008 on the highest warning level. The code AbstractClass.h : #include <iostream> template<typename T> class AbstractClass { public: virtual void Cancel(); // { std::cout << "Abstract Cancel" << std::endl; }; virtual void Process() = 0; }; //outside definition. if I comment out this and take the inline //definition like above (currently commented out), I don't get //a compiler warning template<typename T> void AbstractClass<T>::Cancel() { std::cout << "Abstract Cancel" << std::endl; } Child.h : #include "AbstractClass.h" class Child : public AbstractClass<int> { public: virtual void Process(); }; Child.cpp : #include "Child.h" #include <iostream> void Child::Process() { std::cout << "Process" << std::endl; } The warning The class "Child" is derived from "AbstractClass". In "AbstractClass" there's the public method "AbstractClass::Cancel()". If I define the method outside of the class body (like in the code you see), I get the compiler warning... AbstractClass.h(7) : warning C4505: 'AbstractClass::Cancel' : unreferenced local function has been removed with [T=int] ...when I compile "Child.cpp". I do not understand this, because this is a public function and the compiler can't know if I later reference this method or not. And, in the end, I reference this method, because I call it in main.cpp and despite this compiler warning, this method works if I compile and link all files and execute the program: //main.cpp #include <iostream> #include "Child.h" int main() { Child child; child.Cancel(); //works, despite the warning } If I do define the Cancel() function as inline (you see it as out commented code in AbstractClass.h), then I don't get the compiler warning. Of course my program works, but I want to understand this warning or is this just a compiler mistake? Furthermore, if do not implement AbsctractClass as a template class (just for a test purpose in this case) I also don't get the compiler warning...?

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  • Using nested public classes to organize constants

    - by FrustratedWithFormsDesigner
    I'm working on an application with many constants. At the last code review it came up that the constants are too scattered and should all be organized into a single "master" constants file. The disagreement is about how to organize them. The majority feel that using the constant name should be good enough, but this will lead to code that looks like this: public static final String CREDITCARD_ACTION_SUBMITDATA = "6767"; public static final String CREDITCARD_UIFIELDID_CARDHOLDER_NAME = "3959854"; public static final String CREDITCARD_UIFIELDID_EXPIRY_MONTH = "3524"; public static final String CREDITCARD_UIFIELDID_ACCOUNT_ID = "3524"; ... public static final String BANKPAYMENT_UIFIELDID_ACCOUNT_ID = "9987"; I find this type of naming convention to be cumbersome. I thought it might be easier to use public nested class, and have something like this: public class IntegrationSystemConstants { public class CreditCard { public static final String UI_EXPIRY_MONTH = "3524"; public static final String UI_ACCOUNT_ID = "3524"; ... } public class BankAccount { public static final String UI_ACCOUNT_ID = "9987"; ... } } This idea wasn't well received because it was "too complicated" (I didn't get much detail as to why this might be too complicated). I think this creates a better division between groups of related constants and the auto-complete makes it easier to find these as well. I've never seen this done though, so I'm wondering if this is an accepted practice or if there's better reasons that it shouldn't be done.

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  • Can someone provide a short code example of compiler bootstrapping?

    - by Jatin
    This Turing award lecture by Ken Thompson on topic "Reflections on Trusting Trust" gives good insight about how C compiler was made in C itself. Though I understand the crux, it still hasn't sunk in. So ultimately, once the compiler is written to do lexical analysis, parse trees, syntax analysis, byte code generation etc, a separate machine code is again written to do all that on compiler? Can anyone please explain with a small example of the procedure? Bootstrapping on wiki gives good insights, but only a rough view on it. PS: I am aware of the duplicates on the site, but found them to be an overview which I am already aware

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