main

问题 We can write a java program with one non-public class containing a main method -- it'll compile and run just fine. Why do people make the main class public? Is there any benefit? 回答1: There is no benefit of making the class public for the sake of it having a main method. That being said, there isn't really much of a reason not to either. Chances are the main class is either going to be very short with few, if any, substantial methods in it, or it's going to be baked into one of the core

问题 Using the code below I am getting strange output: import sys from multiprocessing import Process import time from time import strftime now =time.time() print time.strftime("%Y%m%d %H:%M:%S", time.localtime(now)) fr= [1,2,3] for row in fr: print 3 print 1 def worker(): print 'worker line' time.sleep(1) sys.exit(1) def main(): print 'start worker' Process(target=worker, args=()).start() print 'main line' if __name__ == "__main__": start_time = time.time() main() end_time = time.time() duration

问题 My main function is as follows: int main(int argc, char const *argv[]) { huffenc(argv[1]); return 0; } The compiler returns the warning: huffenc.c:76: warning: passing argument 1 of ‘huffenc’ discards qualifiers from pointer target type For reference, huffenc takes a char* input, and the function is executed, with the sample input "senselessness" via ./huffenc senselessness What could this warning mean? 回答1: It means that you're passing a const argument to a function which takes a non- const

问题 Is is possible to register a function to be run immediately before main is entered? I know that all global objects are created before entering main , so I could put the code in the constructor of a global object, but that does not guarantee any particular order. What I would like to do is put some registration code into the constructor, but alas, I don't know what to put there :) I guess this is highly system-specific? 回答1: If you're using gcc , you can use the constructor attribute on a

问题 why is it mandatory to pass string arg[] as an argument in main method? why we cannot pass any other data type available in java? whats the importance of passing String arg[] in main method in java? 回答1: History. This is a convention since the days of C, maybe even earlier? Java took most of its syntax from C. Also, command line arguments are Strings which is why that is the data type. Collections did not exist in Java 1 so they were not an option. Arrays did exist. 回答2: Because by passing

问题 While trying to localize a SpriteKit game i suddenly started getting the error: "Could not find a storyboard named 'Main' in bundle NSBundle" I wasn't use a storyboard, and i think i actually deleted the file when i first started developing the game. 'Main storyboard file base name' was set to 'Main' (was set before as well when it worked and there was no storyboard). I deleted that entry and now the program just executes the AppDelegate file and essentially stops. What's missing where before

问题 I ran this program in GCC(gcc version 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04.3)) on Linux. It successfully compiled using gcc myprog.c and run without any warnings or errors. So, Why doesn't the compiler give any warnings or errors when only one argument is provided for main in C? #include <stdio.h> int main(int i) { printf("%d\n", i); } 回答1: With GCC 6 (on Linux/Debian/Sid/x86-64) my compiler does give some warning when compiling with gcc -Wall rsp.c -o rsp your rsp.c example. rsp.c:3:5: warning

问题 In C++, it is advisable to declare global variables inside the main program, or outside it, before everything else? I mean, what is the difference between #include <iostream> int variable; int main() { //my program return 0; } and #include <iostream> int main() { int variable; //my program return 0; } In which case should I use which one? 回答1: In the first case variable is accessible from all other functions in the file (i.e. it has global scope) whereas in the second case it is only

问题 Does someone know if I have a script one.py which is written the following way: if __name__ == '__main__': # Do something And I want to call that main function from another script. How should I do that? I guess it would be something like (let's say this is launcher.py ) # 'one' stands for import from `one.py` module import one if __name__ == '__main__': one.main() The only problem is that I can't call main() this way. How should this be done? 回答1: with file('a.py','rU') as f: co=compile(f

问题 This question already has answers here : What should main() return in C and C++? (17 answers) Closed 3 years ago . I was going through a tutorial and i have read there, that we can not define void main() as the prototype is already defined as int main() or int main(int argc , char *argv) these are only two valid way to define main function in C. so in which header file or library files these prototype are set I don't how compiler giving me error in case of float main() what is the mechanism