boolean

问题 I can't believe that the following statement seems to be still true So, I switched to integers and 0 or 1 works fine, but it is stupid, that the database system has boolean variables of a smaller size, but I should use integers for boolean values! How do you use boolean datatype with Postgres / PHP? In other words, Is the only way to use 1 for true and 0 for false in getting the kind of the boolean datatype? 回答1: Using 1 and 0 is a very sensible and portable way to represent boolean values.

问题 Given an IP Address and port number, is it possible to check if the machine with that IP address has Postgresql listening on the specified port? If so, how? I just want to obtain a boolean value of whether Postgresql is listening on the specified port of the specified machine. 回答1: I think you need to define what you're trying to achieve better. Do you just want to know if anything is listening on a certain point? If PostgreSQL is listening on a given port? If PostgreSQL is running and

问题 It's not very important but I was just curious to know the difference. echo isA("A"); //outputs 1 echo isA("B"); //outputs nothing. why doesn't it output 0? Anybody can shed somelight on this matter? It does seem to me as a double standard when you look at it from the point of view that "true" outputs as "1" but "false"does not output "0". Again, no big deal but I think there must be a reason for PHP to be designed like that. Knowing that may give some more insight into this beautiful

问题 It's not very important but I was just curious to know the difference. echo isA("A"); //outputs 1 echo isA("B"); //outputs nothing. why doesn't it output 0? Anybody can shed somelight on this matter? It does seem to me as a double standard when you look at it from the point of view that "true" outputs as "1" but "false"does not output "0". Again, no big deal but I think there must be a reason for PHP to be designed like that. Knowing that may give some more insight into this beautiful

问题 It's not very important but I was just curious to know the difference. echo isA("A"); //outputs 1 echo isA("B"); //outputs nothing. why doesn't it output 0? Anybody can shed somelight on this matter? It does seem to me as a double standard when you look at it from the point of view that "true" outputs as "1" but "false"does not output "0". Again, no big deal but I think there must be a reason for PHP to be designed like that. Knowing that may give some more insight into this beautiful

问题 Is there ever a situation where using equals(Boolean) and == would return different results when dealing with Boolean objects? Boolean.TRUE == myBoolean; Boolean.TRUE.equals(myBoolean); I'm not thinking about primitive types here, just Boolean objects. 回答1: How about: System.out.println(new Boolean(true) == new Boolean(true)); System.out.println(new Boolean(true) == Boolean.TRUE); (both print false, for the same reason as any other type of objects). 回答2: It would be dangerous to use ==

问题 I'm redesigning a class constructor in C++ and need it to catch an unspecified bool. I have used default values for all of the other parameters, but from my understanding bool can only be initialized to true or false. Since both of those cases have meaning in the class, how should I handle checking for change from a default value? 回答1: The reality is that you can't do this. A bool has value, either true or false, and if you haven't initialized it then it is randomly true or false, possibly

问题 Let's say I have a function: template <bool stuff> inline void doSomething() { if(stuff) { cout << "Hello" << endl; } else { cout << "Goodbye" << endl; } } And I call it like this: doSomething<true>(); doSomething<false>(); It would pring out: Hello Goodbye What I'm really wondering is does the compiler fully optimize this? When I call the templated function with true, will it create a function that just outputs "Hello" and avoids the if statement and the code for "Goodbye"? This would be

问题 I did a little search on this but couldn't find anything useful. The point being that if String value is either "true" or "false" the return value should be true. In every other value it should be false. I tried these: String value = "false"; System.out.println("test1: " + Boolean.parseBoolean(value)); System.out.println("test2: " + Boolean.valueOf(value)); System.out.println("test3: " + Boolean.getBoolean(value)); All functions returned false :( 回答1: parseBoolean(String) returns true if the

问题 In C++ I'd write something like this: if (a == something && b == anotherthing) { foo(); } Am I correct in thinking the Clojure equivalent is something like this: (if (= a something) (if (= b anotherthing) (foo))) Or is there another way to perform a logical "and" that I've missed? As I said the latter form seems to work correctly--I was just wondering if there's some simpler way to perform the logical and. And searching for "boolean" "logical" and "and" on the Clojure Google Group turned up