syntactic-sugar

问题 Haskell's record syntax is considered by many to be a wart on an otherwise elegant language, on account of its ugly syntax and namespace pollution. On the other hand it's often more useful than the position based alternative. Instead of a declaration like this: data Foo = Foo { fooID :: Int, fooName :: String } deriving (Show) It seems to me that something along these lines would be more attractive: data Foo = Foo id :: Int name :: String deriving (Show) I'm sure there must be a good reason I

问题 It seems like in most mainstream programming languages, returning multiple values from a function is an extremely awkward thing. The typical solutions are to make either a struct or a plain old data class and return that, or to pass at least some of the parameters by reference or pointer instead of returning them. Using references/pointers is pretty awkward because it relies on side effects and means you have yet another parameter to pass. The class/struct solution is also IMHO pretty awkward

问题 If I'm using @synthesize foo; , what's the difference between the following: // message syntax [myObj setFoo:5]; [myObj foo]; and // dot syntax myObj.foo = 5; myObj.foo; I like the consistency of the dot syntax but I don't know if it's doing something I should be I concerned about. Any additional information would be a great help. 回答1: There is no functional difference between using dot syntax and using message syntax. I find that using message syntax is more consistent with the language as a

问题 I just came across a SQL statement that uses AS to alias tables, like this: SELECT all, my, stuff FROM someTableName AS a INNER JOIN someOtherTableName AS b ON a.id = b.id What I'm used to seeing is: SELECT all, my, stuff FROM someTableName a INNER JOIN someOtherTableName b ON a.id = b.id I'm assuming there's no difference and it's just syntactic sugar, but which of these is more prevalent/wide-spread? Is there any reason to prefer one over the other? Edited to clarify: I appreciate all the

问题 On a lot of browsers I've tested, JavaScript blocks actually return a value. You can test it out in any console: for(var i = 0; i < 10; i++) { var sqrt = Math.sqrt(i); if(Math.floor(sqrt) === sqrt) { i; } } The "return" value is the last square number, that is, 9! But since it isn't an expression I suppose, you can't do this: for(var i = 0; i < 10; i++) { ... } + 5 That doesn't work. It gives + 5 , or 5 , of course, because it's a separate statement. Putting the loop in parentheses obviously

问题 On a lot of browsers I've tested, JavaScript blocks actually return a value. You can test it out in any console: for(var i = 0; i < 10; i++) { var sqrt = Math.sqrt(i); if(Math.floor(sqrt) === sqrt) { i; } } The "return" value is the last square number, that is, 9! But since it isn't an expression I suppose, you can't do this: for(var i = 0; i < 10; i++) { ... } + 5 That doesn't work. It gives + 5 , or 5 , of course, because it's a separate statement. Putting the loop in parentheses obviously

问题 I've been puzzling about this for a while and I've looked around a bit, unable to find any discussion about the subject. Lets assume I wanted to implement a trivial example, like a new looping construct: do..until Written very similarly to do..while do { //Things happen here } until (i == 15) This could be transformed into valid csharp by doing so: do { //Things happen here } while (!(i == 15)) This is obviously a simple example, but is there any way to add something of this nature? Ideally

问题 I've been puzzling about this for a while and I've looked around a bit, unable to find any discussion about the subject. Lets assume I wanted to implement a trivial example, like a new looping construct: do..until Written very similarly to do..while do { //Things happen here } until (i == 15) This could be transformed into valid csharp by doing so: do { //Things happen here } while (!(i == 15)) This is obviously a simple example, but is there any way to add something of this nature? Ideally

问题 I've been puzzling about this for a while and I've looked around a bit, unable to find any discussion about the subject. Lets assume I wanted to implement a trivial example, like a new looping construct: do..until Written very similarly to do..while do { //Things happen here } until (i == 15) This could be transformed into valid csharp by doing so: do { //Things happen here } while (!(i == 15)) This is obviously a simple example, but is there any way to add something of this nature? Ideally

问题 In VB.NET there is the WITH command that lets you omit an object name and only access the methods and properties needed. For example: With foo .bar() .reset(true) myVar = .getName() End With Is there any such syntax within Java? Thanks! 回答1: No. The best you can do, when the expression is overly long, is to assign it to a local variable with a short name, and use {...} to create a scope: { TypeOfFoo it = foo; // foo could be any lengthy expression it.bar(); it.reset(true); myvar = it.getName(