declaration

问题 This is probably a really simple thing but I'm new to C++ so need help. I just want to declare an array in my C++ header file like: int lettersArr[26]; and then define it in a function in the cpp file like: lettersArr[26] = { letA, letB, letC, letD, letE, letF, letG, letH, letI, letJ, letK, letL, letM, letN, letO, letP, letQ, letR, letS, letT, letU, letV, letW, letX, letY, letZ }; but this doesn't work. Have I got the syntax wrong or something? What is the correct way to to this? Thanks a lot

问题 I'm a VB.Net guy. (because I have to be, because the person who signs my check says so. :P) I grew up in Java and I don't generally struggle to read or write in C# when I get the chance. I came across some syntax today that I have never seen, and that I can't seem to figure out. In the following method declaration, what does < T > represent? static void Foo < T >(params T[] x) I have seen used in conjunction with declaring generic collections and things, but I can't for the life of me figure

问题 I saw following piece of code in a legacy project. /* token.c */ struct token id_tokens[MAX_TOKENS]; /* analyse.c (v1) */ extern struct token *id_tokens; /* Raised my eyebrow, id_token declares a pointer */ I insisted on changing analyse.c to contain the declaration as below: /* analyse.c (v2) */ extern struct token id_tokens[]; /* I am happy with this. id_tokens declares array of unspecified size. */ I want v2 because pointer to T is not same as array of T . My friend's counter argumented

问题 When I am compiling the java program I am getting this error: class Appletprac is public, should be declared in a file named Appletprac.java Here is my java code: import java.applet.*; import java.awt.*; // Graphics Class import javax.swing.*; import java.awt.event.*; /*<applet code="Appletprac.class" width="500" height="500"> </applet>*/ public class Appletprac extends JApplet implements ActionListener { JButton OK; JRadioButton Font_Style1,Font_Style2,Font_Style3; ButtonGroup bg; JCheckBox

问题 No matter whether I define the function after the variable var a = 1; function a() {}; typeof a // number Or if I define the function before the variable function a() {}; var a = 1; typeof a // number the final typeof result is always number I found some explanation about execution context in http://davidshariff.com/blog/what-is-the-execution-context-in-javascript/ Before executing the function code, create the execution context. ...... Scan the context for variable declarations: If the

问题 This code compiles fine: extern int i = 10; void test() { std::cout << "Hi" << i << std::endl; } While this code gives an error: void test() { extern int i = 10; std::cout << "Hi" << i << std::endl; } error: 'i' has both 'extern' and initializer I read this in C++ Primer: Any declaration that includes an explicit initializer is a definition. We can provide an initializer on a variable defined as extern, but doing so overrides the extern. An extern that has an initializer is a definition. It

问题 I was updating a legacy code base in Java and I found a line like this: Object arg[] = { new Integer(20), new Integer(22) }; That line catched my attention because I am used to this kind of code: Object[] arg = { new Integer(20), new Integer(22) }; The content of the array isn't important here. I'm curious about the brackets next to the variable name versus the brackets next to the class name. I tried in Eclipse (with Java 5) and both lines are valid for the compiler. Is there any difference

问题 #include <stdio.h> struct context; struct funcptrs{ void (*func0)(context *ctx); void (*func1)(void); }; struct context{ funcptrs fps; }; void func1 (void) { printf( "1\n" ); } void func0 (context *ctx) { printf( "0\n" ); } void getContext(context *con){ con=?; // please fill this with a dummy example so that I can get this working. Thanks. } int main(int argc, char *argv[]){ funcptrs funcs = { func0, func1 }; context *c; getContext(c); c->fps.func0(c); getchar(); return 0; } I am missing

问题 When we design classes in Java, Vala, or C# we put the definition and declaration in the same source file. But in C++ it is traditionally preferred to separate the definition and declaration in two or more files. What happens if I just use a header file and put everything into it, like Java? Is there a performance penalty or something? 回答1: The answer depends on what kind of class you're creating. C++'s compilation model dates back to the days of C, and so its method of importing data from

问题 This question already has answers here : Closed 9 years ago . Possible Duplicate: Should C++ eliminate header files? In languages like C# and Java there is no need to declare (for example) a class before using it. If I understand it correctly this is because the compiler does two passes on the code. In the first it just "collects the information available" and in the second one it checks that the code is correct. In C and C++ the compiler does only one pass so everything needs to be available