optional-parameters

I am trying to write a print function for a binary tree and here is what I have so far: impl TreeNode { fn print(&self) { self.print(0); } fn print(&self, level: u8) { for _i in range(0,level) { print!("\t"); } match self.data { Some(x) => println!("{}",x), None => () }; match self.left { Some(ref x) => x.print(level+1), None => () }; match self.right { Some(ref x) => x.print(level+1), None => () }; } } I am getting the error: duplicate definition of value print . So I was wondering if there is a way to create functions with the same name but different arguments. Alternatively optional

This question already has an answer here: Optional parameters on delegates doesn't work properly [duplicate] 4 answers Is there a chance to make this code work? Of course I can make second definition of Foo, but I think it'd be a little non-elegant ;) delegate int Del(int x); static int Foo(int a, int b = 123) { return a+b; } static void Main() { Del d = Foo; } Your delegate asks for exactly one parameter , while your Foo() method asks for at most two parameters (with the compiler providing default values for unspecified call arguments). Thus the method signatures are different, so you can't

According to Functions on GigaMonkeys, Common Lisp supports optional positional parameters via &optional and the default value can be set arbitrarily. The default default value is nil . (defun function (mandatory-argument &optional optional-argument) ... ) and the default value can be set arbitrarily (defun function (mandatory-argument &optional (optional-argument "")) ....) Is there a way of distinguishing the cases where the optional parameter has the default value explicitly passed in vs no value at all? EDIT: evidently the page I linked explains this. Occasionally, it's useful to know

How can I make a method have default values for parameters? A simple solution is to overload the method: private void Foo(int length) { } private void Foo() { Foo(20); } You can only do this in C# 4, which introduced both named arguments and optional parameters : public void Foo(int x = 10) { Console.WriteLine(x); } ... Foo(); // Prints 10 Note that the default value has to be a constant - either a normal compile-time constant (e.g. a literal) or: The parameterless constructor of a value type default(T) for some type T Also note that the default value is embedded in the caller's assembly

In my interface I have declared this. [OperationContract] [WebGet] String GetStuff(String beep, String boop = "too lazy to type"); I implemented it as follows. String GetStuff(String beep, String boop = "too lazy to type") { ... } It compiles and uploads as my WCF service. However, when I used it as a web reference and try to execute the code below, I get the compiler whining and weeping about no method with signature of a single parameter. The last line is the problem. How can I then be too lazy to type by default ? ServiceClient client = new ServiceClient(); client.GetStuff("blobb", "not

No, not answered there ↑ I wonder if I should be using optional parameters in C#. Until now I was always overloading methods. But optional parameters are nice too, cleaner and less code. And I use them in other languages so I'm also used to them in some way. Is there anything that speaks against using them ? Performance is the first key point for me. Would it drop ? Example code: class Program { // overloading private static void test1(string text1) { Console.WriteLine(text1 + " " + "world"); } private static void test1(string text1, string text2) { Console.WriteLine(text1 + " " + text2); } //

From Objective C Programming Guide (Under the "Object Messaging" section), Methods that take a variable number of parameters are also possible, though they’re somewhat rare. Extra parameters are separated by commas after the end of the method name. (Unlike colons, the commas are not considered part of the name.) In the following example, the imaginary makeGroup: method is passed one required parameter (group) and three parameters that are optional: [receiver makeGroup:group, memberOne, memberTwo, memberThree]; I tried to create such a method and it shows an error "Expected ';' after method