arguments

问题 I have a function that takes a member of a particular class: public function addPage(My_Page $page) { // ... } I'd like to make another function that takes an array of My_Page objects: public function addPages($pages) { // ... } I need to ensure that each element of $pages array is an instance of My_Page. I could do that with foreach($pages as $page) and check for instance of , but can I somehow specify in the function definition that the array has to be an array of My_Page objects?

问题 I have a function that takes a member of a particular class: public function addPage(My_Page $page) { // ... } I'd like to make another function that takes an array of My_Page objects: public function addPages($pages) { // ... } I need to ensure that each element of $pages array is an instance of My_Page. I could do that with foreach($pages as $page) and check for instance of , but can I somehow specify in the function definition that the array has to be an array of My_Page objects?

问题 How do I pass in optional arguments to a function in R? An example of this is I might want to be make a function out of a certain combination of hyperparameters for a model. However, I don't want to configure ALL of the hyperparameters as many aren't relevant in most scenarios. From time to time I would like to be able to manually pass in that one hyper-parameter I'd like to change. I often see the ... in functions, but can't figure out if that is relevant to this situation or at least how to

问题 How do I pass in optional arguments to a function in R? An example of this is I might want to be make a function out of a certain combination of hyperparameters for a model. However, I don't want to configure ALL of the hyperparameters as many aren't relevant in most scenarios. From time to time I would like to be able to manually pass in that one hyper-parameter I'd like to change. I often see the ... in functions, but can't figure out if that is relevant to this situation or at least how to

问题 I'm confused how ... works. tt = function(...) { return(x) } Why doesn't tt(x = 2) return 2 ? Instead it fails with the error: Error in tt(x = 2) : object 'x' not found Even though I'm passing x as argument ? 回答1: Because everything you pass in the ... stays in the ... . Variables you pass that aren't explicitly captured by a parameter are not expanded into the local environment. The ... should be used for values your current function doesn't need to interact with at all, but some later

问题 I'm confused how ... works. tt = function(...) { return(x) } Why doesn't tt(x = 2) return 2 ? Instead it fails with the error: Error in tt(x = 2) : object 'x' not found Even though I'm passing x as argument ? 回答1: Because everything you pass in the ... stays in the ... . Variables you pass that aren't explicitly captured by a parameter are not expanded into the local environment. The ... should be used for values your current function doesn't need to interact with at all, but some later

问题 I am trying to pass multiple file path arguments via command line to an Rscript which can then be processed using an arguments parser. Ultimately I would want something like this Rscript test.R --inputfiles fileA.txt fileB.txt fileC.txt --printvar yes --size 10 --anotheroption helloworld -- etc... passed through the command line and have the result as an array in R when parsed args$inputfiles = "fileA.txt", "fileB.txt", "fileC.txt" I have tried several parsers including optparse and getopt

问题 void restartWeb() { try { String[] command = new String[] {"webRestarter.exe" , ">>","webLog.log"}; Runtime.getRuntime().exec(command); } catch (java.io.IOException err) { webServer.logError(err.getMessage()); } } Why doesn't this work? How could I fix it so it does work like I want it to? -- Executes webRestarter.exe with parameters >>webLog.log So it'd spit out something like this: webRestarter.exe>>webLog.log 回答1: You simply can't use pipes in a exec call. Pipes are a functionality of the

问题 void restartWeb() { try { String[] command = new String[] {"webRestarter.exe" , ">>","webLog.log"}; Runtime.getRuntime().exec(command); } catch (java.io.IOException err) { webServer.logError(err.getMessage()); } } Why doesn't this work? How could I fix it so it does work like I want it to? -- Executes webRestarter.exe with parameters >>webLog.log So it'd spit out something like this: webRestarter.exe>>webLog.log 回答1: You simply can't use pipes in a exec call. Pipes are a functionality of the

问题 Question: I want to write an function to print an array from mth element to nth element where m<=n and if a is an array then function calling should looks like print(a+m,a+n). Noow what should be the user defined function for this case? #include <stdio.h> #include <iostream> using namespace std; /* It may be ok or not. If not then what program should write? */ void print(int a[], int n) { for(int i=0;; ++i){ if(a[i] == a[n]) break; printf("%d ",a[i]); } } int main() { int a[6] = {1,3,5,6,8,2}