post-increment

问题 During a programming class, the professor was teaching us about x++ and ++x , with x being an integer. He said that in the scenario we are able to just put either x++ or ++x , ++x is more efficient (by little, but still, in theory, more efficient nonetheless). But I forgot why . Anyone knows? This was with Java. 回答1: It's not more efficient in Java. It can be more efficient in languages where the increment/decrement operators can be overloaded, but otherwise the performance is exactly the

问题 During a programming class, the professor was teaching us about x++ and ++x , with x being an integer. He said that in the scenario we are able to just put either x++ or ++x , ++x is more efficient (by little, but still, in theory, more efficient nonetheless). But I forgot why . Anyone knows? This was with Java. 回答1: It's not more efficient in Java. It can be more efficient in languages where the increment/decrement operators can be overloaded, but otherwise the performance is exactly the

问题 I don't understand the results of following code: #include <stdio.h> #include <conio.h> int main() { int a[4]={1, 3, 5, 6}; //suppose a is stored at location 2010 printf("%d\n", a + 2); printf("%d", a++); return 0; } Why does the second printf function produce following error? error: lvalue required as increment operand 回答1: Part-1: Array names are constant (not modifiable lvalue), your can add value to array name but can't modify it. Expression a + 2 doesn't modify a itself but when you do a

问题 This question already has answers here : Closed 10 years ago . Exact Duplicate : Is there a performance difference between i++ and ++i in C++? Exact Duplicate : Difference between i++ and ++i in a loop? What is more efficient, i++ or ++i? I have only used this in Java and C/C++, but I am really asking for all languages that this is implemented in. In college I had a professor show us that ++i was more efficient, but it has been a couple of years, and I would like to get input from the Stack

问题 Does spaces have any meaning in these expressions: assume: int a = 1; int b = 2; 1) int c = a++ +b; Or, 2) int c = a+ ++b; When I run these two in visual studio, I get different results. Is that the correct behavior, and what does the spec says? In general, what should be evaluated first, post-increment or pre-increment? Edit: I should say that c =a+++b; Does not compile on visual studio. But I think it should. The postfix++ seems to be evaluated first. 回答1: Is that the correct behavior Yes,

问题 I had come across this answer to this question. In one of the line, the author mention's: In any case, follow the guideline "prefer ++i over i++ " and you won't go wrong. I know that ++i is slightly faster than i++ , but thought that there is no reason for them to go wrong. I searched for a while, and the closest I could get to was this. It explained clearly that why is it preferred to use ++i , but not still how could you go wrong using i++ . So can anyone tell me how can i++ go wrong? NOTE:

问题 This question already has answers here : Why are these constructs using pre and post-increment undefined behavior? (14 answers) printf(“%d %d %d\n”,++a, a++,a) output [duplicate] (3 answers) Closed 2 years ago . If n has the value 5 then output: printf("%d %d", n++, ++n); //should be 5 and 7 But I get as output 6 and 7. 回答1: Multiple unsequenced modifications result to such kind of Undefined Behavior . There are tons of results if you search for it, e.g. this question. Next time compile with

问题 I am really new to programming (I'm an electronics and comm. engineer) and I am not able to figure out why one program works and the other one doesn't. I'd like to get a good understanding of recursive functions before going any further with my learning. I would appreciate any help regarding this. I know the difference between the x++ and --x. But in this context of this program, I thought both of these programs should run the same way. But they don't. void rec(int x) { if(x>0) rec(x--);

问题 package com.android.tapme; import android.os.Bundle; import android.app.Activity; import android.widget.*; import android.view.*; public class TapMe extends Activity { private int countValue=0; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_tap_me); checkTapValue(); } private void checkTapValue() { Button tapButton=(Button)findViewById(R.id.tapButton); tapButton.setOnClickListener(new View.OnClickListener() {

问题 I'm working through K&R and am presently on Exercise 1-16. It occurs to me that thus far only pre-increment has been used in the book. Most other tutorial books and indeed source code I've seen tend to favour post-increment, except where there is an obvious affect such as in while loops etc. Is this a stylistic or technical consideration on the part of K&R? Or do I just need to be further through the book to get my answer?! 回答1: There are several aspects to this. Semantics The semantics of