ternary-operator

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 In the PHP manual, I find the following 'user contributed note' under "Operators". Note that in php the ternary operator ?: has a left associativity unlike in C and C++ where it has right associativity. You cannot write code like this (as you may have accustomed to in C/C++): <?php $a = 2; echo ( $a == 1 ? 'one' : $a == 2 ? 'two' : $a == 3 ? 'three' : $a == 4 ? 'four' : 'other'); echo "\n"; // prints 'four' I actually try it and it really prints four . However I could not understand the

问题 Why is this printing 2 ? echo true ? 1 : true ? 2 : 3; With my understanding, it should print 1 . Why is it not working as expected? 回答1: Because what you've written is the same as: echo (true ? 1 : true) ? 2 : 3; and as you know 1 is evaluated to true . What you expect is: echo (true) ? 1 : (true ? 2 : 3); So always use braces to avoid such confusions. As was already written, ternary expressions are left associative in PHP. This means that at first will be executed the first one from the

问题 Why is this printing 2 ? echo true ? 1 : true ? 2 : 3; With my understanding, it should print 1 . Why is it not working as expected? 回答1: Because what you've written is the same as: echo (true ? 1 : true) ? 2 : 3; and as you know 1 is evaluated to true . What you expect is: echo (true) ? 1 : (true ? 2 : 3); So always use braces to avoid such confusions. As was already written, ternary expressions are left associative in PHP. This means that at first will be executed the first one from the

问题 It's more about python list comprehension syntax. I've got a list comprehension that produces list of odd numbers of a given range: [x for x in range(1, 10) if x % 2] This makes a filter - I've got a source list, where I remove even numbers ( if x % 2 ). I'd like to use something like if-then-else here. Following code fails: >>> [x for x in range(1, 10) if x % 2 else x * 100] File "<stdin>", line 1 [x for x in range(1, 10) if x % 2 else x * 100] ^ SyntaxError: invalid syntax There is a python

问题 This is what I wrote : $Myprovince = ( ($province == 6) ? "city-1" : ($province == 7) ? "city-2" : ($province == 8) ? "city-3" : ($province == 30) ? "city-4" : "out of borders" ); But for every field I got the value city-4 . I want to use ternary operators instead of switch/if because I want to experiment and see how it would be done. What's the problem with this code? 回答1: Others have already suggested the right way of doing it but if you really want to use ternary operator you need to use

问题 I have : #include<stdio.h> int main() { int a=5,b=6; (a>b)?b=a:b=b; // Here is the error return 0; } But if I replace : (a>b)?b=a:b=b; // Error with (a>b)?(b=a):(b=b); // No-Error I understand the lvalue is a value to which something can be assigned and how is it different from rvalue , but why is the extra parenthesis making the difference. 回答1: Assignment has a lower precedence than the ternary operator so the line evaluates like: ((a>b)?b=a:b)=b; use: b=(a>b)?a:b; 回答2: Actually, in C, this

问题 I have : #include<stdio.h> int main() { int a=5,b=6; (a>b)?b=a:b=b; // Here is the error return 0; } But if I replace : (a>b)?b=a:b=b; // Error with (a>b)?(b=a):(b=b); // No-Error I understand the lvalue is a value to which something can be assigned and how is it different from rvalue , but why is the extra parenthesis making the difference. 回答1: Assignment has a lower precedence than the ternary operator so the line evaluates like: ((a>b)?b=a:b)=b; use: b=(a>b)?a:b; 回答2: Actually, in C, this

问题 How do you do a ternary with AngularJS (in the templates)? It would be nice to use some in html attributes (classes and style) instead of creating and calling a function of the controller. 回答1: Update : Angular 1.1.5 added a ternary operator, so now we can simply write <li ng-class="$first ? 'firstRow' : 'nonFirstRow'"> If you are using an earlier version of Angular, your two choices are: (condition && result_if_true || !condition && result_if_false) {true: 'result_if_true', false: 'result_if

问题 How do you do a ternary with AngularJS (in the templates)? It would be nice to use some in html attributes (classes and style) instead of creating and calling a function of the controller. 回答1: Update : Angular 1.1.5 added a ternary operator, so now we can simply write <li ng-class="$first ? 'firstRow' : 'nonFirstRow'"> If you are using an earlier version of Angular, your two choices are: (condition && result_if_true || !condition && result_if_false) {true: 'result_if_true', false: 'result_if