conditional-operator

问题 Note: I solved the original problem by realizing a completely different one. See the addendum for the new actual problem, but you can read the previous part for context. This is an extension of one of my previous posts. I made a container class based on that answer: template < typename T, unsigned N0, unsigned ...N > struct array_md { // There's a class template specialization with no extents. // Imagine the various N... components are bracket-enclosed instead // of comma-separated. And if "N

问题 I was just wondering, is there a shortcut for logical operator( && , || ). Like if I want to do something like i = i + 10 , I can do i += 10 Reason I'm searching this is because I have a validation function which is divided into several functions. Following is a simulation: function f1(){ return Math.ceil(Math.random()*10) %2 === 0? true:false } function f2(){ return Math.ceil(Math.random()*10) %2 === 0? true:false } function f3(){ return Math.ceil(Math.random()*10) %2 === 0? true:false }

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 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 There is an error. Is it wrong to assign a value to a[i] in the following code? Or something is wrong with conditional operators? #include<stdio.h> #include<string.h> int main(){ char a[12]="sumit tyagi"; int i=0; while(a[i]!='\0'){ a[i]>90 ? a[i]=a[i]-32 : a[i]=a[i]+32; //error in this line i++; } printf("\n %s",a); 回答1: a[i]>90 ? a[i]=a[i]-32 : a[i]=a[i]+32; is not evaluated as a[i]>90 ? (a[i]=a[i]-32) : (a[i]=a[i]+32); since = has lower precedence than ?: . In standard C you can't write it

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 I have run in to some weird thing when I want to print one of my objects (which is obviously not null). If I use this line: text.append("\n [ITEM ID]: " + (item == null ? (otherItem == null ? 0 : otherItem .getItems().get(i).getId()) : item .getItems().get(i).getId())); There is no null pointer exception if my item object is null . Of course this should be the excepted result. But if I use it without the () marks: text.append("\n [ITEM ID]: " + item == null ? (otherItem == null ? 0 :

问题 When I run this script: #!/bin/bash if [[ "abcd" =~ ^.*$ ]]; then echo "something" fi I get: ./tmp2.sh: line 3: conditional binary operator expected ./tmp2.sh: line 3: syntax error near `=~' ./tmp2.sh: line 3: `if [[ "abcd" =~ ^.*$ ]]; then' I've tried all suggestions I've found, but still the same:/ Help me, please! 回答1: Given that you're seeing a bash-specific error message , we can rule out that something other than bash is running the script (if it were a POSIX-features-only shell, such

问题 This question already has answers here : Java Ternary without Assignment (4 answers) Closed 6 months ago . When I attempted to compile the following Java program: public class MyClass { static int f1() { return 10; } static int f2() { return 20; } public static void main(String args[]) { int x = 10; (x <= 10) ? f1() : f2(); } } I got the error: /MyClass.java:9: error: not a statement (x <= 10) ? f1() : f2(); ^ Java language definition talks about statements as one of assignment, increment

问题 Consider the following code: int x; int& f() { return x ? x : throw 0; } With gcc version 7.3.0 (Ubuntu 7.3.0-27ubuntu1~18.04) I get the following compilation error: cannot bind non-const lvalue reference of type ‘int&’ to an rvalue of type ‘int’ Note that this compiles just fine in clang. Here is (what I believe to be) the relevant statement from the standard: N4659 [8.16.2.1] (Conditional Operator): The second or the third operand (but not both) is a (possibly parenthesized) throw