arguments

问题 I want to write a function that takes a dataframe, and graphs all the columns in that dataframe as histograms. For a dataframe whose column names I know beforehand, I can write qplot(colname1, data=df, geom='histogram') qplot(colname2, data=df, geom='histogram') ... but I want to do this generically, so that I can use the name of the column as a string "colname1" . In other words, how to write plot_histogram_of_column <- function(df, colname) { # qplot(colname, data=df, geom='histogram') won

问题 The range function in python3 takes three arguments two of them are optional. So the argumentlist looks like: [start], stop, [step] so this means (correct me if i'm wrong) there is a optional argument before an not-optional argument. But if i try to define a function like this i get this: >>> def foo(a = 1, b, c = 2): print(a, b, c) SyntaxError: non-default argument follows default argument is this something i can't do as a 'normal' python user, or can i somehow define such a function? Of

问题 I am using a bash script to call and execute a .jar file from any location without having to constantly enter its explicit path. The .jar requires additional variable parameters to be specified at execution, and as these can be anything, they cannot be hard coded into the script. There are 3 variables in total, the first specifies 1 of 2 actions that the .jar is to make, the second specifies a target file to enact this action on and the third specifies the name of a file that the action is to

问题 In php how would you create a function that could take an unlimited number of parameters: myFunc($p1, $p2, $p3, $p4, $p5...); My next question is: how would you pass them into another function something like function myFunc($params){ anotherFunc($params); } but the anotherFunc would receive them as if it was called using anotherFunc($p1, $p2, $p3, $p4, $p5...) 回答1: call_user_func_array('anotherFunc', func_get_args()); func_get_args returns an array containing all arguments passed to the

问题 In php how would you create a function that could take an unlimited number of parameters: myFunc($p1, $p2, $p3, $p4, $p5...); My next question is: how would you pass them into another function something like function myFunc($params){ anotherFunc($params); } but the anotherFunc would receive them as if it was called using anotherFunc($p1, $p2, $p3, $p4, $p5...) 回答1: call_user_func_array('anotherFunc', func_get_args()); func_get_args returns an array containing all arguments passed to the

问题 I have a method that returns a map defined as: public Map<String, ?> getData(); The actual implementation of this method is not clear to me, but, when I try to do: obj.getData().put("key","value") I get following compile time error message: The method put(String, capture#9-of ?) in the type Map is not applicable for the arguments (String, String) What is the problem? Is String not of type anything? Thanks in advance. 回答1: The wildcard means "the value type parameter could be anything" - it

问题 I keep reading posts which say that ActionListener methods must have the following signiture: public void calledByActionListener(ActionEvent e) { } Invoked like so: <p:commandButton value="Example" id="example" process="@this" ajax="false" actionListener="#{exampleBean.calledByActionListener()}"> However I have a no-arg method like this which works: public void calledByActionListener() { } Did something change? 回答1: Yes, that's the new EL 2.2 feature of invoking methods with custom arguments.

问题 Is there any way to pass values and variables between php scripts? Formally, I tried to code a login page and when user enter wrong input first another script will check the input and if it is wrong, site returns to the last script page and show a warning like "It is wrong input". For this aim, I need to pass values from scripts I guess. Regards... :P 回答1: To pass info via GET : header('Location: otherScript.php?var1=val1&var2=val2'); Session : // first script session_start(); $_SESSION[

问题 Is there any way to pass values and variables between php scripts? Formally, I tried to code a login page and when user enter wrong input first another script will check the input and if it is wrong, site returns to the last script page and show a warning like "It is wrong input". For this aim, I need to pass values from scripts I guess. Regards... :P 回答1: To pass info via GET : header('Location: otherScript.php?var1=val1&var2=val2'); Session : // first script session_start(); $_SESSION[

问题 Can I pass arrays to functions just as I would do with primitives such as int and bool? Can I pass them by value? How does the function know of the size of the array it is passed? 回答1: Can I pass arrays to functions just as I would do with primitives such as int and bool? Yes, but only using pointers (that is: by reference). Can I pass them by value? No. You can create classes that support that, but plain arrays don't. How does the function know of the size of the array it is passed? It doesn