argument-passing

What are [function] arguments? What are they used for? I started learning Python very recently; I'm new to programming and I apologize for this basic question. In every Python tutorial I go through they talk about arguments . I have looked for the answer to this question and have found many answers but they are just a little too hard for me to understatnd. I may just be missing some conceptual background. So... when I define a function, what are the things in parenthesis used for? Example: def hi( This is the part that i dont get): print 'hi' Edit: Two follow-up questions related to this one

A lot of MATLAB functions have an input structure such as: output = function MyFun(a,b,c,'-setting1',s1,'-setting2',s2,'-setting3',s3) I am wondering how I should implement this kind of functionality in my own functions. To be precise, I would like to find out how I can create a function such that: The function has a variable number of inputs N + M The first N inputs are ordered and unlabeled . In the example above, N = 3 . The first input is always a , second input is always b , third input is always c . The function input is variable in that users do not necessarily need to send b , c ; when

Is it possible to pass a function pointer as an argument to a function in C? If so, how would I declare and define a function which takes a function pointer as an argument? Mehrdad Afshari Definitely. void f(void (*a)()) { a(); } void test() { printf("hello world\n"); } int main() { f(&test); return 0; } Michal Sznajder Let say you have function int func(int a, float b); So pointer to it will be int (*func_pointer)(int, float); So than you could use it like this func_pointer = func; (*func_pointer)(1, 1.0); /*below also works*/ func_pointer(1, 1.0); To avoid specifying full pointer type every

How do I check if an optional argument was passed to a method? public void ExampleMethod(int required, string optionalstr = "default string", int optionalint = 10) { if (optionalint was passed) return; } Another approach is to use Nullable<T>.HasValue ( MSDN definitions , MSDN examples ): int default_optionalint = 0; public void ExampleMethod(int required, int? optionalint, string optionalstr = "default string") { int _optionalint = optionalint ?? default_optionalint; } Well, arguments are always passed. Default parameter values just ensure that the user doesn't have to explicitly specify them

I would like to create a Listener class class Listener { var $listeners = array(); public function add(callable $function) { $this->listeners[] = $function; } public function fire() { foreach($this->listeners as $function) { call_user_func($function); } } } class Foo { public function __construct($listener) { $listener->add($this->bar); } public function bar() { echo 'bar'; } } $listener = new Listener(); $foo = new Foo($listener); But this code fails with this error: Notice: Undefined property: Foo::$bar in index.php on line 18 Catchable fatal error: Argument 1 passed to Listener::add() must

I am writing a function in which I want to pass some arguments to the crrstep-function ('crrstep' package), but I encountered a problem: somehow the argument 'event' in my function is not recognized when I enter it in crrstep. I guess that crrstep looks in a different environment than the one I want it to look, but even after hours of searching for solutions on the web, I cannot seem to figure out how to solve this (I am quite inexperienced in programming..). Any help would be greatly appreciated! Here is some simulation data (adjusted example from crrstep-documentation) and an example of my

Most of the applications we developers write need to be externally parametrized at startup. We pass file paths, pipe names, TCP/IP addresses etc. So far I've been using command line to pass these to the appplication being launched. I had to parse the command line in main and direct the arguments to where they're needed, which is of course a good design , but is hard to maintain for a large number of arguments. Recently I've decided to use the environment variables mechanism. They are global and accessible from anywhere, which is less elegant from architectural point of view, but limits the

I am trying to write a function wo which you can parse a variable amount of arguments via argparse - I know I can do this via nargs="+" . Sadly, the way argparse help works (and the way people generally write arguments in the CLI) puts the positional arguments last. This leads to my positional argument being caught as part of the optional arguments. #!/usr/bin/python import argparse parser = argparse.ArgumentParser() parser.add_argument("positional", help="my positional arg", type=int) parser.add_argument("-o", "--optional", help="my optional arg", nargs='+', type=float) args = parser.parse

I need to get an argument and convert it to an int. Here is my code so far: #include <iostream> using namespace std; int main(int argc,int argvx[]) { int i=1; int answer = 23; int temp; // decode arguments if(argc < 2) { printf("You must provide at least one argument\n"); exit(0); } // Convert it to an int here } Since this answer was somehow accepted and thus will appear at the top, although it's not the best, I've improved it based on the other answers and the comments. The C way; simplest, but will treat any invalid number as 0: #include <cstdlib> int x = atoi(argv[1]); The C way with input