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  • What does =*> mean with regards to context free grammars?

    - by incrediman
    I've been reading a couple books/online references about compiler theory, and keep seeing that particular operator coming up every once in a while (as seen here), specifically when the current topic is context free grammars. What does it mean? As well, how does it differ from =>? Explanations with examples distinguishing => from =*> would be most helpful.

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  • Why isn't the boost::shared_ptr -> operator inlined?

    - by Alan
    Since boost::shared_ptr could be called very frequently and simply returns a pointer, isn't the -> operator a good candidate for being inlined? T * operator-> () const // never throws { BOOST_ASSERT(px != 0); return px; } Would a good compiler automatically inline this anyway? Should I lose any sleep over this? :-)

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  • C: performance of assignments, binary operations, et cetera...

    - by Shinka
    I've heard many things about performance in C; casting is slow compared to normal assignments, functional call is slow, binary operation are much faster than normal operations, et cetera... I'm sure some of those things are specific to the architecture, and compiler optimization might make a huge difference, but I would like to see a chart to get a general idea what I should do and what I should avoid to write high-performance programs. Is there such a chart (or a website, a book, anything) ?

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  • 'Scanner' does not name a type error in g++

    - by Max
    Hi. I'm trying to compile code in g++ and I get the following errors: In file included from scanner.hpp:8, from scanner.cpp:5: parser.hpp:14: error: ‘Scanner’ does not name a type parser.hpp:15: error: ‘Token’ does not name a type Here's my g++ command: g++ parser.cpp scanner.cpp -Wall Here's parser.hpp: #ifndef PARSER_HPP #define PARSER_HPP #include <string> #include <map> #include "scanner.hpp" using std::string; class Parser { // Member Variables private: Scanner lex; // Lexical analyzer Token look; // tracks the current lookahead token // Member Functions <some function declarations> }; #endif and here's scanner.hpp: #ifndef SCANNER_HPP #define SCANNER_HPP #include <iostream> #include <cctype> #include <string> #include <map> #include "parser.hpp" using std::string; using std::map; enum { // reserved words BOOL, ELSE, IF, TRUE, WHILE, DO, FALSE, INT, VOID, // punctuation and operators LPAREN, RPAREN, LBRACK, RBRACK, LBRACE, RBRACE, SEMI, COMMA, PLUS, MINUS, TIMES, DIV, MOD, AND, OR, NOT, IS, ADDR, EQ, NE, LT, GT, LE, GE, // symbolic constants NUM, ID, ENDFILE, ERROR }; class Token { public: int tag; int value; string lexeme; Token() {tag = 0;} Token(int t) {tag = t;} }; class Num : public Token { public: Num(int v) {tag = NUM; value = v;} }; class Word : public Token { public: Word() {tag = 0; lexeme = "default";} Word(int t, string l) {tag = t; lexeme = l;} }; class Scanner { private: int line; // which line the compiler is currently on int depth; // how deep in the parse tree the compiler is map<string,Word> words; // list of reserved words and used identifiers // Member Functions public: Scanner(); Token scan(); string printTag(int); friend class Parser; }; #endif anyone see the problem? I feel like I'm missing something incredibly obvious.

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  • How to make a private property?

    - by mystify
    I tried to make a private property in my *.m file: @interface MyClass (Private) @property (nonatomic, retain) NSMutableArray *stuff; @end @implementation MyClass @synthesize stuff; // not ok Compiler claims that there's no stuff property declared. But there's a stuff. Just in an anonymous category. Let me guess: Impossible. Other solutions?

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  • Qt inheriting from QGraphicsEllipseItem

    - by JHollanti
    I was trying to inherit from QGraphicsEllipseItem 'cause i wanted to add some functionality to it. However i was faced with this error, which probably has something to do with the compiler/precompiler or moc? error: 'staticMetaObject' is not a member of 'QGraphicsEllipseItem' And here's the class code: class MyEllipseItem : public QGraphicsEllipseItem { Q_OBJECT public: MyEllipseItem (const QRectF & outline) : QGraphicsEllipseItem(outline) { } };

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  • C++ delete[] operator

    - by Betamoo
    Is this the right way to use delete[] operator? int* a=new int[size]; delete[] a; If yes, Who (compiler or GC or whoever) will determine the size of the newly created array? and where will it store the array size? Thanks

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  • How to make a macro which gives back a string into the source code?

    - by mystify
    Example: I want to do this: METHODNAME(5) { // do something } which results in: - (void)animationStep5 { // do something } Is there any way to do this? Basically, what I need is a way to generate a real source code string before the program is compiled, so the compiler does see - (void)animationStep5... Or maybe there's something different than a macro, which can help here to auto-generate method names (not at run-time)?

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  • A program that creates another program

    - by zaidwaqi
    Hi, I need to create a program that creates another program but not a compiler though. For example, I write a program that accepts a string input from the user. Let's say user enter "Pluto". This program should then create a separate .exe that says "Hello Pluto" when executed. How can I do this? If you could give example in C# and Windows Forms, it's better. Thanks.

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  • Object of an abstract class

    - by webgenius
    Why is it not possible to create an object of an abstract class? I understand that the compiler creates a VTABLE with VPTR pointing to NULL. Does this prevent from creating an object of an abstract class?

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  • what happens when two exceptions occur?

    - by ashish yadav
    what will the operating system and compiler behave when they have two exceptions. And none of them have been caught yet. what type of handler will be called . lets say both the exceptions were of different type. i apologize if i am not clear but i feel i have made myself clear enough. thank you!!!

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  • How is it possible to legally write ::: in C++ and ??? in C#?

    - by daveny
    These questions are a kind of game, and I did not find the solution for them. It is possible to write ::: in C++ without using quotes or anything like this and the compiler will accept it (macros are prohibited too). And the same is true for C# too, but in C#, you have to write ???. I think C++ will use the :: scope operator and C# will use ? : , but I do not know the answers to them. Any idea?

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  • c++ volatile multithreading variables

    - by anon
    I'm writing a C++ app. I have a class variable that more than one thread is writing to. In C++, anything that can be modified without the compiler "realizing" that it's being changed needs to be marked volatile right? So if my code is multi threaded, and one thread may write to a var while another reads from it, do I need to mark the var volaltile? [I don't have a race condition since I'm relying on writes to ints being atomic] Thanks!

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  • jquery datepicker in asp.net

    - by Abu Hamzah
    whats wrong with the below code, its throwing me an error of Compiler Error Message: CS1002: ; expected $(document).ready(function() { $('<%StartDate%>').datepicker({ showOn: 'button', buttonImage: '../images/Calendar.png', buttonImageOnly: true, onSelect: function() { }, onClose: function() { $(this).focus(); } }); }); <label for="sd">StartDate:</label> <asp:TextBox ID="StartDate" runat="server"></asp:TextBox>

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  • F# constructor syntax - overiding and augmenting new

    - by Benjol
    I have a non-disposable class with Open/Close syntax that I'd like to be able to use, so I'm trying to inherit from it, and work the Open into the new and the Close into Dispose. The second part is ok, but I can't work out how to do the Open: type DisposableOpenCloseClass(openargs) = inherit OpenCloseClass() //do this.Open(openargs) <-- compiler no like interface IDisposable with member this.Dispose() = this.Close() (cf. this question which I asked a long time ago, but I can't join the dots to this one)

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  • problem in printing floating point

    - by kudi
    hi I am using IAR c compiler, I am trying to print floating point value like printf("version number: %f\n",1.4); but I am always getting like below in console version number:ERROR help please thanks in advance kudi

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  • getting started with Google Closure if you don't compare about minifying/compiling?

    - by Tim
    If you don't care about minifying your code, is there a way to get started using the Google Closure library without having to set up a subversion client and use the compiler? The Notepad sample program on Google's website refers to <script src="closure-library/base.js" > </script > Can you simply download closure-library/base.js somewhere and start playing with the UI examples? The Closure Lite quick-start version doesn't appear to include goog.ui

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  • How can I write a "Hello World" app in assembly language?

    - by SLC
    I've often heard of applications written using the language of the gods, assembly language. I've never tried though, and I don't even have a clue how to do it. If I wanted to dabble, how would I go about doing it? I know absolutely nothing about what is required, although presumably some kind of compiler and Notepad. Just purely out of curiousity, what would I need to write a "Hello World!" application?

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  • Odd behaviour with scala method syntax

    - by Ceilingfish
    Hi chaps, I hit a bit of a quirk of scala's syntax I don't really understand object Board { def getObjectAt(x:Int, y:Int):Placeable = return locations(x)(y) } works fine. But object Board { def getObjectAt(x:Int, y:Int):Placeable { return locations(x)(y) } } returns the error Board.scala:8: error: illegal start of declaration return locations(x)(y) I found some stuff that says the second form convinces the scala compiler you're trying to specify an expansion to the return type Placeable. Is there a way I can fix this, or should I just avoid specifying a return type here?

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  • initializing a readonly property. Object c

    - by tak
    i was trying to create a property which is readonly. i wanted to initialize with a value from the class creating an instance of this class.e.g @property (readonly) NSString *firstName; And wanted to initialize it like -(id)initWithName:(NSString *)n{ self.firstName = n; } Once i do this, this compiler shows an error that the readonly property cannot be assigned. So how can i do this?

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