definition | 易学教程

What is the definition of “array” in C?

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问题 The standard defines array type meticulously, but I don't see any definition for array . We might say "object of array type", however that can't be right as untyped objects (e.g. space allocated by malloc ) is described as an array. Motivation: The specification for %s in fprintf (C11 7.21.6.1/8) says: the argument shall be a pointer to the initial element of an array of character type but take the code char s[] = "hello"; printf("%s", s+1); then we passed a pointer to the second element.

What exactly does “closure” refer to in JavaScript?

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I understand what closures are, but I am having some trouble grokking exactly what the term closure refers to. I have seen the term used in many websites, but rarely do they agree on the actual definition of it. Is it the variables that are kept on the stack frame? Is it the function that is being returned? Is it the scope of the outer function? Is it the scope of the inner (returned) function? Is it maybe the concept of keeping the variables on the stack-frame after returning the function? Can someone tell me exactly to what closure refers to? rahul From JavaScript Closures Two one-sentence

Javascript local variable declare

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问题 Basically this is a question how to access local scope handler. I trying to achieve something similar for global variable definition like: window['newObject'] = "some string"; alert(newObject); but for local scope. Right now only solution I have is using evals: eval("var newObject='some string'"); But this is really ugly solution... The best one would be like using some reference to local scope like in a window[] solution, but I never heard of any reference to local scope... Any ideas ?

What is a “thread” (really)?

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I have been trying to find a good definition, and get an understanding, of what a thread really is. It seems that I must be missing something obvious, but every time I read about what a thread is, it's almost a circular definition, a la "a thread is a thread of execution" or " a way to divide into running tasks". Uh uh. Huh? It seems from what I have read that a thread is not really something concrete, like a process is. It is in fact just a concept. From what I understand of the way this works, a processor executes some commands for a program (which has been termed a thread of execution ),

What is boilerplate code?

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问题 A coworker had never heard of this, and I couldn't provide a real definition. For me, it's always been an instance of 'I-know-it-when-I-see-it'. Bonus question, who originated the term? 回答1: "boilerplate code" is any seemingly repetitive code that shows up again and again in order to get some result that seems like it ought to be much simpler. It's a subjective definition. The term comes from "boilerplate" in the newspaper industry: wiki 回答2: On the etymology the term boilerplate : from http:

Defining function without the brackets?

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问题 I understand that my question might sound stupid, and that there might be something in the language definition that explicitly prohibits this notion, but since I don't know about this prohibition, I was wondering whether someone could shed some light on it. In short, I would like to define a python function that I could call from the python shell, but I would like to avoid the brackets. There are cases when a function does not require an argument, and then the bracket only seems to indicate

ReferenceError: variable is not defined

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I met this issue sometimes but still don't know what causes it. I have this script in the page: $(function(){ var value = "10"; }); But the browser says "ReferenceError: value is not defined". However if I go to the browser console and input either 10 or var value = "10"; either of them can return 10. What is the problem with my script? Edit:just get rid of "var" can solve the problem. It's declared inside a closure, which means it can only be accessed there. If you want a variable accessible globally, you can remove the var : $(function(){ value = "10"; }); value; // "10" This is equivalent

Declaration or Definition in C

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问题 From External Variables Wiki: If neither the extern keyword nor an initialization value are present, the statement can be either a declaration or a definition. It is up to the compiler to analyse the modules of the program and decide. I was not able to fully grasp the meaning of this statement with respect to C. For example, does it imply that: int i; is not necessarily a declaration (as I have been assuming until now), but could be a definition as well (by definition of Definition &

Error with multiple definitions of function

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I am trying to relearn C++ after taking an intro course a few years ago and I’m having some basic problems. My current problem occurs when trying to use a friend function. Here is my code in 2 files. First: // fun.cpp #include <iostream> using namespace std; class classA { friend void funct(); public: classA(int a=1,int b=2):propa(a),propb(b){cout<<"constructor\n";} private: int propa; int propb; void outfun(){ cout<<"propa="<<propa<<endl<<"propb="<<propb<<endl; } }; void funct(){ // ERROR HERE cout<<"enter funct"<<endl; classA tmp(1,2); tmp.outfun(); cout<<"exit funct"<<endl; } Second: //

What is a loop invariant?

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I'm reading "Introduction to Algorithm" by CLRS. In chapter 2, the authors mention "loop invariants". What is a loop invariant? Tomas Petricek In simple words, a loop invariant is some predicate (condition) that holds for every iteration of the loop. For example, let's look at a simple for loop that looks like this: int j = 9; for(int i=0; i<10; i++) j--; In this example it is true (for every iteration) that i + j == 9 . A weaker invariant that is also true is that i >= 0 && i <= 10 . TNi I like this very simple definition: ( source ) A loop invariant is a condition [among program variables]