ternary-operator

问题 Given two implementations of Comparison methods: // compares by Key... private static int CompareByKey(KeyValuePair<int, string> x, KeyValuePair<int, string> y) { return x.Key.CompareTo(y.Key); } // compares by Value... private static int CompareByValue(KeyValuePair<int, string> x, KeyValuePair<int, string> y) { return x.Value.CompareTo(y.Value); } Why wouldn't the following conditional operator code block compile: Comparison<KeyValuePair<int, string>> sortMethod; sortMethod =

问题 Here I am trying to change the value of the following check box while clicking on it. In the code below I tried to change the value of the checkbox to 1 and change the value to 0 when unchecked. But it takes only the false condition, when the checkbox is unchecked the value changes to 0 but when checked its not changing to 1. Any suggestions how to fix this out ? <input type="checkbox" id="read" name="permission[]" onClick="($(this).checked)?$(this).attr('value',1):$(this).attr('value',0)"/>

问题 New to javascript and I'm having trouble counting the number of trues in an array of boolean values. I'm trying to use the reduce() function. Can someone tell me what I'm doing wrong? //trying to count the number of true in an array myCount = [false,false,true,false,true].reduce(function(a,b){ return b?a++:a; },0); alert("myCount ="+ myCount); // this is always 0 回答1: Seems like your problem is solved already, but there are plenty of easier methods to do it. Array.prototype.filter() - the

问题 Apologies if this has been asked before, but I couldn't see it anywhere. Essentially I've come across a scenario where i need to make use of an if statement inside a lambda function. What makes it difficult is that ideally it needs to be in a single line of code (if thats even possible?) Normally, i would write this: T = 250 if (T > 200): rate = 200*exp(-T) else: rate = 400*exp(-T) return (rate) However i need it to look like this: rate = lambda(T) : if (T>200): return(200*exp(-T)); else:

问题 Netbeans is saying that my ternary operator isn't a statement. How come? int direction; direction = (Math.random() < 0.5) ? 0 : 1; // direction is either L or R (0 or 1) direction == 0 ? System.out.print('L') : System.out.print('R'); I tried it's if/then/else counterpart and it works fine: int direction; direction = (Math.random() < 0.5) ? 0 : 1; // direction is either L or R (0 or 1) if(direction == 0){ System.out.print('L'); } else { System.out.print('R'); } 回答1: The statements in the

问题 This question already has answers here : ?: ternary conditional operator behaviour when leaving one expression empty (2 answers) Closed 5 years ago . Typically the '?' operator is used in the following form: A ? B : C However in cases where B = A I have seen the following abbreviation A ? : C This surprisingly works. Is it better to leave the second parameter in (style wise), or is their a chance certain compilers won't be able to handle this? 回答1: It is not permitted by the language C (as

问题 When branching to select a function, it might make sense to use the ternary operator to select a function, but this is impossible. Why? public class Demo { protected bool branch; protected void demo1 () {} protected void demo2 () {} public Action DoesntWork() { return branch ? demo1 : demo2; } } The compiler produces the following error: Cannot implicitly convert type `method group' to `System.Action' 回答1: The problem is that demo1 is not a simple expression, it is a method . And methods can

问题 Is there a ternary operator or the like in PHP that acts like ?? of C#? ?? in C# is clean and shorter, but in PHP you have to do something like: // This is absolutely okay except that $_REQUEST['test'] is kind of redundant. echo isset($_REQUEST['test'])? $_REQUEST['test'] : 'hi'; // This is perfect! Shorter and cleaner, but only in this situation. echo null? : 'replacement if empty'; // This line gives error when $_REQUEST['test'] is NOT set. echo $_REQUEST['test']?: 'hi'; 回答1: PHP 7 adds the

问题 This question already has answers here : Closed 10 years ago . Possible Duplicate: quick php syntax question return $add_review ? FALSE : $arg; What do question mark and colon mean? Thanks 回答1: This is the PHP ternary operator (also known as a conditional operator) - if first operand evaluates true, evaluate as second operand, else evaluate as third operand. Think of it as an "if" statement you can use in expressions. Can be very useful in making concise assignments that depend on some

问题 This question already has answers here : What are the PHP operators “?” and “:” called and what do they do? (9 answers) Closed 2 years ago . $items = (isset($_POST['items'])) ? $_POST['items'] : array(); I don't understand the last snippet of this code " ? $_POST['items'] : array(); " What does that combination of code do exactly? I use it to take in a bunch of values from html text boxes and store it into a session array. But the problem is, if I attempt to resubmit the data in text boxes