boolean

问题 This question already has answers here : What does !! (double exclamation point) mean? (3 answers) Closed 6 years ago . Okay so I came across a code which looks like @documents_names = sort { !!$deleted_documents_names{$a} == !!$deleted_documents_names{$b} ? uc($a) cmp uc($b) : !!$deleted_documents_names{$a} cmp !!$deleted_documents_names{$b} } @documents_names; It's the first time I'm seeing the use of double negation. What's the use of it? When would a person use it? 回答1: It converts non

问题 I have to write a program in which main calls other functions that test a series of number if any are less than a number, if all the series' numbers are between two limits, and if any are negative. My code returns the values of 1 for true and 0 for false, but the assignment asks that they be printed as 'true' or 'false'. I'm not sure how to get the bool answers to print as a string from printf. I used if (atl == false) printf("false"); in my at_least.c and in main.c, but it returns only a

问题 GCC seems to allow "and" / "or" to be used instead of "&&" / "||" in C++ code; however, as I expected, many compilers (notably MSVC 7) do not support this. The fact that GCC allows this has caused some annoyances for us in that we have different developers working on the same code base on multiple platforms and occasionally, these "errors" slip in as people are switching back and forth between Python and C++ development. Ideally, we would all remember to use the appropriate syntax, but for

问题 Using QT Designer to design the code. Then using the pyuic5 -x productentryscreen.ui > productentryscreen3.py command to generate python code. i am using buttons and textboxes. when a button is pressed i want to display value entered in the QlineEdit box. But i am getting the error " AttributeError: 'bool' object has no attribute" when the btnCancel is clicked. This is where the error is thrown (i presume) textboxValue = self.txtCustCode.text . i even tried with textboxValue = self

问题 Beginners question in cakePHP, it drives me mad, I tried so much but can't get this working in cakePHP. I want to print 'Train station nearby' if the boolean is set. The database has the field 'train' bit(1) when doing a <?php echo h($property['Property']['train']); ?> it shows 1 but in the database it is 0, WHY is it printing 1 instead of 0 <?php if($property['Property']['train'] == true ) echo 'Train station nearby'; ?> This output works all the time, but of course it is not true! Anyone

问题 Beginners question in cakePHP, it drives me mad, I tried so much but can't get this working in cakePHP. I want to print 'Train station nearby' if the boolean is set. The database has the field 'train' bit(1) when doing a <?php echo h($property['Property']['train']); ?> it shows 1 but in the database it is 0, WHY is it printing 1 instead of 0 <?php if($property['Property']['train'] == true ) echo 'Train station nearby'; ?> This output works all the time, but of course it is not true! Anyone

问题 When I cast to Boolean (using (bool) ), is there a built in way to get PHP to actually return the constants true or false . At the moment I'm getting 1 or blank, which evaluate to true and false respectively. I want the value returned for clearer semantics. However, if I can't get it, I'll just settle with 1 and blank. 回答1: PHP displays boolean values as 1 (true) or empty string (false) when outputted. If you want to check if it's true or false use == (if implicit conversion is OK) or === (if

问题 When I cast to Boolean (using (bool) ), is there a built in way to get PHP to actually return the constants true or false . At the moment I'm getting 1 or blank, which evaluate to true and false respectively. I want the value returned for clearer semantics. However, if I can't get it, I'll just settle with 1 and blank. 回答1: PHP displays boolean values as 1 (true) or empty string (false) when outputted. If you want to check if it's true or false use == (if implicit conversion is OK) or === (if

问题 When I cast to Boolean (using (bool) ), is there a built in way to get PHP to actually return the constants true or false . At the moment I'm getting 1 or blank, which evaluate to true and false respectively. I want the value returned for clearer semantics. However, if I can't get it, I'll just settle with 1 and blank. 回答1: PHP displays boolean values as 1 (true) or empty string (false) when outputted. If you want to check if it's true or false use == (if implicit conversion is OK) or === (if

问题 I am teaching myself to program using Swift 3, and I am currently learning about booleans. I noticed that if I want to explicitly declare my variable of type bool, I have two options Bool or Boolean I was wondering why we have these two options if they are the same? Well, are they the same? This is what I'm confused about. Thanks in advance. 回答1: Bool is Swift's boolean data type. Boolean hasn't existed since the early days of Swift. 来源： https://stackoverflow.com/questions/40776830/swift-bool