while-loop | 易学教程

Stop a infinite while loop pressing a key in Matlab

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问题 I have a while loop, infinite, and I want to stop it when I press a keyboard key. Pseudocode: While(1) do stuff; listening for key; if key is pressed break; end end The function waitforbuttonpress makes me press the key, so no luck. I've found no option on the web. 回答1: I suppose if you don't want to resort to multithreading (one thread doing the computation in the while loop, another one waiting for input and setting a global sentinel value to break the while loop) you can try to implement

Parallel while Loops in Python

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问题 I'm pretty new to Python, and programming in general and I'm creating a virtual pet style game for my little sister. Is it possible to run 2 while loops parallel to each other in python? eg: while 1: input_event_1 = gui.buttonbox( msg = 'Hello, what would you like to do with your Potato Head?', title = 'Main Screen', choices = ('Check Stats', 'Feed', 'Exercise', 'Teach', 'Play', 'Go to Doctor', 'Sleep', 'Change Favourite Thing', 'Get New Toy', 'Quit')) if input_event_1 == 'Check Stats':

Why is my program looping too many times?

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问题 I'm a beginner in C and trying to create a program and having a problem with my main function. Problem: After asking how many integers they'd like to enter, for example: 4 numbers, the loop goes on 5 times essentially taking in 5 numbers. It also only prints "Next: " after the 2nd number. In my while loop, which I put for error checking, after the user puts a valid method, example: enters 1, it will print out that it's an "invalid choice" and re-asks again only once more. Code: #include

How to limit items from while loop

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问题 This is my while loop from my project : <?php $select = "SELECT * FROM nk_showcase"; $query = $db->rq($select); while ($user = $db->fetch($query)) { ?> <div class="index"> <a href="details.php?id=<?php echo $user['id']; ?>"><img width="200" height="171" alt="<?php echo $user['title']; ?>" src="<?php echo $url; ?>/images/niagakit/<?php echo $user['thumb']; ?>"/></a> <h3><a href="<?php echo $url; ?>/"><?php echo $user['title']; ?></a></h3> <p><a href="<?php echo $url; ?>/"><?php echo $user['url

Running 'prop.test' multiple times in R

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问题 I have some data showing a long list of regions, the population of each region and the number of people in each region with a certain disease. I'm trying to show the confidence intervals for each proportion (but I'm not testing whether the proportions are statistically different). One approach is to manually calculate the standard errors and confidence intervals but I'd like to use a built-in tool like prop.test, because it has some useful options. However, when I use prop.test with vectors,

How to exit a while-loop?

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问题 #include <stdio.h> main(void) { char ch; while (1) { if ((ch = getchar()) != EOF) { break; } putchar(ch); } return 0; } How do I escape from this while ? I had tried with EOF but it didn't work. 回答1: I think you mean: int ch; Because EOF won't fit in a char . Also: if ((ch=getchar()) == EOF) break; Your logic is backwards. 回答2: This: char ch; is wrong, EOF doesn't fit in a char . The type of getchar() 's return value is int so this code should be: int ch; Also, as pointed out, your logic is

Leaks while adding to array in while loop

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I have function named: - (void) AddSortedCustomFeed :(NSMutableArray*) rssList; this function adds items(Articles) from sqlite database to NSMutableArray here how this function works: - (void) AddSortedCustomFeed :(NSMutableArray*)rssList { NSLog(@"\n\n\n ----- Add Sorted SQL Database -----"); NSLog(@"Start"); // Create Query String. NSString* sqliteQuery = [NSString stringWithFormat:@"SELECT mainLink, title, summary, pubDate, author, imageLink, body, favorites, pubdatetime FROM ARTICLES WHERE customfeed = 'Y' ORDER BY pubdatetime DESC"]; NSLog(@"Query String is: %@", sqliteQuery); // Pointer

Input string with getchar

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问题 I am trying to read a string into a char array with a length chosen by the user. The problem is that getchar() doesn't stop reading until the user manually enters a newline by pressing enter, based on my code. I have read through other's threads, and I understand why I'm not able to do it this way, it's just completely contradictory to my assignment handout. int chPrompt(int nchars); void strInput(char str[], int nchars); int main(void) { int nchars = chPrompt(nchars); char str[nchars];

Infinite loop problem with while loop and threading [duplicate]

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问题 This question already has an answer here : Loop doesn't see value changed by other thread without a print statement (1 answer) Closed 5 years ago . Using a basic example to illustrate my problem I have 2 near-identical bits of code. This code causes the while loop to run infinitely. private boolean loadAsset() { new Thread(new Runnable() { @Override public void run() { // Do something loaded = true; } }).start(); while (!loaded) { // System.out.println("Not Loaded"); } System.out.println(

PostgreSQL: Loop Until a Condition is True

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问题 I am trying to write a query which "loops" through a database starting at a specified value until a condition is true. For example, suppose I have the following entries in TABLE example: id, parent, cond 1, , True 2, 1 , False 3, 1 , False 4, 2 , False ... ... ... I want a query which takes as input (for instance) 4, and will return the values of 2 and 1. The process being that the query matches the id, and if cond==False, will look at the parent (id = 2). Since cond = False in the second row