conditional-operator

问题 Is it possible to do one line if statement in VB .NET? If so, how? 回答1: Use IF(). It is a short-circuiting ternary operator. Dim Result = IF(expression,<true return>,<false return>) SEE ALSO: IIF becomes If, and a true ternary operator Is there a conditional ternary operator in VB.NET? Orcas introduces the IF operator - a new and improved IIF The Ternary Operator in VB.NET 回答2: It's actually pretty simple.. If CONDITION Then ..INSERT CODE HERE.. 回答3: At the risk of causing some cringing by

问题 I want to load two difference panel in .xhtml file. <h:inputText value="#{param['from']=='TERMINAL' ? terminalsList.globalFilter : merchantsList.globalFilter}" size="50" /> <h:commandButton value="Filter" actionListener="#{param['from']=='TERMINAL' ? terminalsList.filterTerminals : merchantsList.filterMerchants}" /> <h:commandButton value="Reset" actionListener="#{param['from']=='TERMINAL' ? terminalsList.resetTerminalsFilter : merchantsList.resetMerchantsFilter}" /> when http get request

问题 I have this extract of C# 2.0 source code: object valueFromDatabase; decimal result; valueFromDatabase = DBNull.Value; result = (decimal)(valueFromDatabase != DBNull.Value ? valueFromDatabase : 0); result = (valueFromDatabase != DBNull.Value ? (decimal)valueFromDatabase : (decimal)0); The first result evaluation throws an InvalidCastException whereas the second one does not. What is the difference between these two? 回答1: UPDATE: This question was the subject of my blog on May 27th 2010.

问题 In the Android open-source qemu code I ran across this line of code: machine->max_cpus = machine->max_cpus ?: 1; /* Default to UP */ Is this just a confusing way of saying: if (machine->max_cpus) { ; //do nothing } else { machine->max_cpus = 1; } If so, wouldn't it be clearer as: if (machine->max_cpus == 0) machine->max_cpus = 1; Interestingly, this compiles and works fine with gcc, but doesn't compile on http://www.comeaucomputing.com/tryitout/ . 回答1: This is permitted in GNU as an obscure

问题 I really like this: var value = maxValue > minValue ? minValue : maxValue; Is there something equally concise in Coffescript? 回答1: value = if maxValue > minValue then minValue else maxValue 回答2: There is a more concise option in both javascript and coffeescript :) value = Math.min(minValue, maxValue) 回答3: As Răzvan Panda points out, my comment may actually one of the better answers: value = `maxValue > minValue ? minValue : maxValue` 回答4: This is a case where it feels like CoffeeScript has

问题 This question already has answers here : How to test multiple variables against a value? (24 answers) Closed last year . I'm learning Python and I'm having a little bit of a problem. Came up with this short script after seeing something similar in a course I'm taking. I've used "or" with "if" before with success (it doesn't show much here). For some reason I can't seem to get this working: test = raw_input("It's the flying circus! Cool animals but which is the best?") x = test.lower() if x ==

问题 In pages like http://en.wikipedia.org/wiki/?: the ternary/conditional operator ?: seems to be used for conditional assignments. I tried to use it for method calling, like this: (condition) ? doThis() : doThat(); Both methods return void. Java tells me it is not a statement. So, I'm guessing I can't do conditional method calling... or can I? 回答1: Think of ternary operators like a method in this case. Saying a ? b : c is (for the intents and purposes you're considering, see lasseespeholt's

问题 I am curious as to why an implicit cast fails in... int? someValue = SomeCondition ? ResultOfSomeCalc() : null; and why I have to perform an explicit cast instead int? someValue = SomeCondition ? ResultofSomeCalc() : (int?)null; It seems to me that the compiler has all the information it need to make an implicit casting decision, no? 回答1: The relevant section of the C# 3.0 spec is 7.13, the conditional operator: The second and third operands of the ?: operator control the type of the

问题 From what I know, PowerShell doesn't seem to have a built-in expression for the so-called ternary operator. For example, in the C language, which supports the ternary operator, I could write something like: <condition> ? <condition-is-true> : <condition-is-false>; If that doesn't really exist in PowerShell, what would be the best way (i.e. easy to read and to maintain) to accomplish the same result? 回答1: $result = If ($condition) {"true"} Else {"false"} Everything else is incidental

问题 I can understand why the assignment operator is right associative. It makes sense that when x = 4 + 3 is evaluated, that 4 and 3 are added before being assigned to x. I am unclear as to how ?: would benefit from being right associative. Does it only matter when two ?: s were used like this z = (a == b ? a : b ? c : d); Then it is evaluated like this: z = (a == b ? a : (b ? c : d)); Surely it would make more sense to evaluate from left to right? 回答1: If it evaluated from left to right, it'd