variable-assignment

问题 I noticed the following when using '[<-' . I am successful at replacing elements but not at appending an element to the vector. Example: VarX <- integer() VarX[1] <- 11 `[<-`(VarX, 2, 22) VarX # [1] 11 # Expected the value of VarX to be: # [1] 11 22 # Also tried: `[<-`(VarX, i=2, value=22) VarX # [1] 11 However, if there is already a value at the index, the value does get replaced. VarX <- integer() VarX[1] <- 11 VarX[2] <- 99 VarX # [1] 11 99 `[<-`(VarX, 2, 22) VarX # [1] 11 22 Do I simply

问题 For example I have a code like that: structure(list(mpg = c(21, 21, 22.8, 21.4, 18.7, 18.1, 14.3, 24.4, 22.8, 19.2, 17.8, 16.4, 17.3, 15.2, 10.4, 10.4, 14.7, 32.4, 30.4, 33.9, 21.5, 15.5, 15.2, 13.3, 19.2, 27.3, 26, 30.4, 15.8, 19.7, 15, 21.4), cyl = c(6, 6, 4, 6, 8, 6, 8, 4, 4, 6, 6, 8, 8, 8, 8, 8, 8, 4, 4, 4, 4, 8, 8, 8, 8, 4, 4, 4, 8, 6, 8, 4), disp = c(160, 160, 108, 258, 360, 225, 360, 146.7, 140.8, 167.6, 167.6, 275.8, 275.8, 275.8, 472, 460, 440, 78.7, 75.7, 71.1, 120.1, 318, 304, 350,

问题 This is a follow-up question to my previous initialization variable question. Suppose we're dealing with this context: object AppProperties { private var mgr: FileManager = _ def init(config: Config) = { mgr = makeFileManager(config) } } The problem with this code is that any other method in AppProperties might reassign mgr . Is there a technique to better encapsulate mgr so that it feels like a val for the other methods? I've thought about something like this (inspired by this answer):

问题 This question already has answers here : Why does substring slicing with index out of range work? (3 answers) Closed 3 years ago . I'm working on a sparse list implementation and recently implemented assignment via a slice. This led me to discover some behaviour in Python's built-in list implementation that I find suprising. Given an empty list and an assignment via a slice: >>> l = [] >>> l[100:] = ['foo'] I would have expected an IndexError from list here because the way this is implemented

问题 I am editing a quick sort code so that the values of low, high, and middle point to an array element instead of integers. This is my code: #include <stdio.h> #define N 10 void quicksort(int a[], int *low, int *high); int split(int a[], int *low, int *high); int main(void) { int a[N], i; printf("Enter %d numbers to be sorted: ", N); for (i=0; i<N; i++) scanf("%d", &a[i]); quicksort(a, &a[0], &a[N-1]); printf("In sorted order: "); for (i=0; i<N; i++) printf("%d ", a[i]); printf("\n"); return 0;

问题 I am editing a quick sort code so that the values of low, high, and middle point to an array element instead of integers. This is my code: #include <stdio.h> #define N 10 void quicksort(int a[], int *low, int *high); int split(int a[], int *low, int *high); int main(void) { int a[N], i; printf("Enter %d numbers to be sorted: ", N); for (i=0; i<N; i++) scanf("%d", &a[i]); quicksort(a, &a[0], &a[N-1]); printf("In sorted order: "); for (i=0; i<N; i++) printf("%d ", a[i]); printf("\n"); return 0;

问题 I came across this line when I was doing some laborations: int home_address = current_pos_ = hash(key, size_); And I was wondering what it actually does? (not the hashfunction or anything, just the "int variable = variable = value;" thing) 回答1: That expression is read as: int home_address = (current_pos_ = hash(key,size_)); It assigns the result of hash(key,size_) into current_pos_ and it then assigns the value of current_pos_ into home_address . 回答2: The assignment operator evaluates to the

问题 I have a class Transaction which has a var amount of type Int . I want to access it from another class, where I have an array of Transactions and sum all of their amounts. So I have this piece of code func computeTotal()-> Int{ let total = 0 for transaction in transactions{ //get the amounts of each and sum all of them up total += transaction.amount } return total } But it gives me an error Cannot invoke "+=" with an argument list of type (Int, @value Int) What can cause that? I know that in

问题 I came across this code and wanted others to provide their point of view... is it good or bad ? ;) Class ReportClass { public string ReportName {get; set;} } Then it was used as follows in code: displayReport(ReportClass.ReportName = cmbReportName.SelectedValue.ToString()) That is about the simplest form example I can give you. Quetion is... why can't I find examples ? What would this be called? Is this just asking for trouble? EDIT: I'm referring to the inplace assignment. Which I wasn't

问题 I have built an empty associative array whos keynames refer to submitted post data. I can capture the postdata just fine, but I run into trouble trying to instantiate variables who's names match the array key. for example: $insArray = array('rUsername'=>'', 'rPass'=>'', 'rQuestion'=>'', 'rAnswer'=>'', 'rFName'=>'', 'rLName'=>'', 'rBDateD'=>'', 'rBDateM'=>'', 'rBDateY'=>'', 'rHCheck'=>'', 'rHCeckOption'=>'', 'rEmail'=>''); foreach($insArray as $key=>$value){ if (filter_input(INPUT_POST, $key)