conditional-statements

问题 I have 4 model: Item------hasMany---->Detail Item------hasMany---->Favourite Item------hasMany---->Category How can I find all Item that has Favourite.member_id = '8' and Category.item_category_id = '1' Here is my Item model relation: public $hasMany = array( 'Detail' => array( 'className' => 'Detail', 'foreignKey' => 'item_id', 'dependent' => true, 'conditions' => '', 'order' => 'created DESC', ), 'Category' => array( 'className' => 'Category', 'foreignKey' => 'item_id', 'dependent' => true,

问题 I have a user model with attributes 'first' and 'last' So for example User.first.first #=> "Charlie" User.first.last #=> "Brown" This User model also has a virtual attribute 'full_name' #user.rb def full_name [first,last].join(' ') end def full_name=(name) #don't know what to do with people w/ middle names split = name.split(' ') self.first = split[0] self.last = split[1] end So for example: User.first.full_name = "Charlie Brown" #=> "Charlie Brown" User.first.full_name = "Homer Simpson" #=>

问题 Ive been thinking about what is the best way to solve this, any advise? The table/matrix X is: X <- read.table(text = " a b c d e 0 27 0 28 8 1 14 24 32 33 0 4 22 25 27 0 3 7 26 34 0 28 33 31 21 0 16 17 24 18 1 3 19 0 12 0 2 23 5 24 2 17 22 22 10 0 35 15 17 2", header = TRUE, stringsAsFactors = FALSE) or using matlab: X =[ 0 27 0 28 8 1 14 24 32 33 0 4 22 25 27 0 3 7 26 34 0 28 33 31 21 0 16 17 24 18 1 3 19 0 12 0 2 23 5 24 2 17 22 22 10 0 35 15 17 2]; How could I obtain a table/matrix A and

问题 I came to R from SAS, where numeric missing is set to infinity. So we can just say: positiveA = A > 0; In R, I have to be verbose like: positiveA <- ifelse(is.na(A),0, ifelse(A > 0, 1, 0)) I find this syntax is hard to read. Is there anyway I can modify ifelse function to consider NA a special value that is always false for all comparison conditions? If not, considering NA as -Inf will work too. Similarly, setting NA to '' (blank) in ifelse statement for character variables. Thanks. 回答1: This

问题 What is the difference between using: if (NULL == pointer) and using: if (pointer == NULL) My professor says to use the former over the latter but I don't see the difference between the two. 回答1: There is no difference. What your professor prefers is called Yoda conditions also see "Yoda Conditions", "Pokémon Exception Handling" and other programming classics. It is supposed to prevent the usage of assignment( = ) by mistake over equality( == ) in a comparison, but modern compilers should

问题 Hey, I have to use IN condition in my MySQL statement with a large set of ids. Example SELECT * FROM users WHERE id IN (1,2,3,4...100000) Is there a limit if items the IN statement can have? 回答1: No there isn't, check the manual about the IN function: The number of values in the IN list is only limited by the max_allowed_packet value. 回答2: As far as I know in mysql, there is no limit for items in the IN statement. In oracle altough, there is a limit of 1000 items in the IN statement. But more

问题 I would like to create a conditional task in Airflow as described in the schema below. The expected scenario is the following: Task 1 executes If Task 1 succeed, then execute Task 2a Else If Task 1 fails, then execute Task 2b Finally execute Task 3 All tasks above are SSHExecuteOperator. I'm guessing I should be using the ShortCircuitOperator and / or XCom to manage the condition but I am not clear on how to implement that. Could you please describe the solution? 回答1: You have to use airflow

问题 I would like to create a conditional task in Airflow as described in the schema below. The expected scenario is the following: Task 1 executes If Task 1 succeed, then execute Task 2a Else If Task 1 fails, then execute Task 2b Finally execute Task 3 All tasks above are SSHExecuteOperator. I'm guessing I should be using the ShortCircuitOperator and / or XCom to manage the condition but I am not clear on how to implement that. Could you please describe the solution? 回答1: You have to use airflow

问题 This question already has answers here : How to test multiple variables against a value? (24 answers) Closed last year . I'm learning Python and I'm having a little bit of a problem. Came up with this short script after seeing something similar in a course I'm taking. I've used "or" with "if" before with success (it doesn't show much here). For some reason I can't seem to get this working: test = raw_input("It's the flying circus! Cool animals but which is the best?") x = test.lower() if x ==

问题 I have to find maximum of three number provided by user but with some restrictions. Its not allowed to use any conditional statement. I tried using ternary operator like below. max=(a>b?a:b)>c?(a>b?a:b):c But again its restricted to use ternary operator. Now I am not getting any idea how to do this? 回答1: Taking advantage of short-circuiting in boolean expressions: int max(int a, int b, int c) { int m = a; (m < b) && (m = b); //these are not conditional statements. (m < c) && (m = c); //these