boolean

问题 I ran across some very interesting code that makes me wonder about what bool is. I've always considered it to be a primitive type, like int or char or long. But today, I saw something that looked like this: void boolPtrTest() { bool thisBool = true; boolPtrHere(thisBool); printf("thisBool is %s\n", thisBool ? "true" : "false"); } void boolPtrHere(bool& theBool) { theBool = false; // uhh, dereferencing anyone? } And this code runs - no errors - and prints "thisBool is false"! To further make

问题 I think i might be going mad. I use console.log() to see the state of an object and then on the next line do a console.log() on a particular property of the same object and get different values for each. The code i'm using is: console.log(this.pictures.Items[pic].val); for(var i in this.pictures.Items[pic].val) { console.log("property: %s, value: %s", i, this.pictures.Items[pic].val[i] ); } and firebug outputs: Picture { isLoaded=true, isSelected=false, img_src="imgs/image1.jpg", more...}

问题 I'm getting a string from a $_GET and I want to test if it could be a boolean, before I use it for a part of a mysql query. Is there a better way of doing it than: function checkBool($string){ $string = strtolower($string); if ($string == "true" || $string == "false" || $string == "1" || $string == "0"){ return true; } else { return false; } } if (checkBool($_GET['male'])){ $result = mysql_query( "SELECT * FROM my_table " . "WHERE male='".$_GET['male']."'") or die(mysql_error()); } 回答1: There

问题 Since I started Java it's been very aggravating for me that it doesn't support implicit conversions from numeric types to booleans, so you can't do things like: if (flags & 0x80) { ... } instead you have to go through this lunacy: if ((flags & 0x80) != 0) { ... } It's the same with null and objects. Every other C-like language I know including JavaScript allows it, so I thought Java was just moronic, but I've just discovered that C# is the same (at least for numbers, don't know about null

问题 The query below is what I would like to construct using elasticsearch-dsl-py, but I do not know how to do it. GET /my_index/_search { "query": { "filtered": { "filter": { "bool": { "must": [ { "term": { "status": "published" } }, { "or": { "filters": [ { "range": { "start_publication": { "lte": "2015-02-17T03:45:00.245012+00:00" } } }, { "missing": { "field": "start_publication" } } ] } }, { "or":{ "filters": [ { "range": { "end_publication": { "gte": "2015-02-17T03:45:00.245012+00:00" } } },

问题 This question already has answers here : Default value of boolean and Boolean in Java (8 answers) Closed 5 years ago . I just want to know if there is a difference in Java between: private boolean someValue; private boolean someValue = false; The second line maybe is just a time wasting? EDIT (SUMMARY): From the answers I found that there is almost no difference, but: "Relying on such default values, however, is generally considered bad programming style." But there are some strong arguments

问题 I'm looking for the way of comparing two strings and being able to get back, as separate strings: All the common characters, The uncommon characters, (all characters but without the common ones) Characters that are unique to one string. Example: A = "123 ABC" B = "135 AZ" thingamajigger(A, B) # would give all these: intersect = "13 A" # (includes space) exclusion = "2BCZ5" a_minus_b = "2BC" b_minus_a = "5Z" a_minus_b is quite simple... but if there's one of those fancy one-liner ways to pull

问题 What is the best way to convert an int or null to boolean value in an SQL query, such that: Any non-null value is TRUE in the results Any null value is FALSE in the results 回答1: To my knowledge (correct me if I'm wrong), there is no concept of literal boolean values in SQL. You can have expressions evaluating to boolean values, but you cannot output them. This said, you can use CASE WHEN to produce a value you can use in a comparison: SELECT CASE WHEN ValueColumn IS NULL THEN 'FALSE' ELSE

问题 Its the same thing right? Or is there a slight difference? I just wanna make sure I'm not misunderstanding anything. 回答1: Boolean duals are generated by simply replacing ANDs with ORs and ORs with ANDs. The complements themselves are unaffected, where as the complement of an expression is the negation of the variables WITH the replacement of ANDs with ORs and vice versa. Consider: A+B Complement: A'B' Dual: AB 回答2: "The Dual of an identity is also an identity. This is called the Duality

问题 I wasn't aware of this, but apparently the and and or keywords aren't operators. They don't appear in the list of python operators. Just out of sheer curiosity, why is this? And if they aren't operators, what exactly are they? 回答1: Because they're control flow constructs. Specifically: if the left argument to and evaluates to False, the right argument doesn't get evaluated at all if the left argument to or evaluates to True, the right argument doesn't get evaluated at all Thus, it is not