Tutorial by Examples: call

You can call a function in Racket by wrapping it in parentheses with the arguments after it. This looks like (function argument ...). > (define (f x) x) > (f 1) 1 > (f "salmon") "salmon" > (define (g x y) (string-append x y)) > (g "large" "sal...

Swift class FooViewController: UIViewController { override func loadView() { view = FooView() } }

A common pitfall of child classes is that, if your parent and child both contain a constructor(__construct()) method, only the child class constructor will run. There may be occasions where you need to run the parent __construct() method from it's child. If you need to do that, then you will need to...

If you need to call an Objective-C method from C code, you have two ways: using objc_msgSend, or obtaining the IMP (method implementation function pointer) and calling that. #import <objc/objc.h> @implementation Example - (double)negate:(double)value { return -value; } - (doubl...

A callback is a method that gets called at specific moments of an object's lifecycle (right before or after creation, deletion, update, validation, saving or loading from the database). For instance, say you have a listing that expires within 30 days of creation. One way to do that is like this: ...

To access functions and properties of nullable types, you have to use special operators. The first one, ?., gives you the property or function you're trying to access, or it gives you null if the object is null: val string: String? = "Hello World!" print(string.length) // Compile erro...

If you have your data stored in a list and you want to convert this list to a data frame the do.call function is an easy way to achieve this. However, it is important that all list elements have the same length in order to prevent unintended recycling of values. dataList <- list(1:3,4:6,7:9) ...

For named (non-anonymous) functions, you can break when the function is executed. debug(functionName); The next time functionName function runs, the debugger will stop on its first line.

Fortran 2003 introduced language features which can guarantee interoperability between C and Fortran (and to more languages by using C as an intermediary). These features are mostly accessed through the intrinsic module iso_c_binding: use, intrinsic :: iso_c_binding The intrinsic keyword here en...

public class Customer { public void SendEmail() { // Sending email code here } } List<Customer> customers = new List<Customer>(); customers.Add(new Customer()); customers.Add(new Customer()); customers.ForEach(c => c.SendEmail());

Callback-based: db.notification.email.find({subject: 'promisify callback'}, (error, result) => { if (error) { console.log(error); } // normal code here }); This uses bluebird's promisifyAll method to promisify what is conventionally callback-based code like above. blueb...

TCO is only available in strict mode As always check browser and Javascript implementations for support of any language features, and as with any javascript feature or syntax, it may change in the future. It provides a way to optimise recursive and deeply nested function calls by eliminating the n...

If you have a function declared you can call it anywhere else in the code. Here is an example of calling a function: void setup(){ Serial.begin(9600); } void loop() { int i = 2; int k = squareNum(i); // k now contains 4 Serial.println(k); delay(500); } int squareNum(int a)...

The call/N family of predicates can call arbitrary Prolog goals at run time: ?- G=true, call(G). true. ?- G=(true,false), call(G). false.

In Prolog, the so-called meta-call is a built-in language feature. All Prolog code is represented by Prolog terms, allowing goals to be constructed dynamically and be used like other goals without additional predicates: ?- Goal = dif(X, Y), Goal. dif(X, Y). Using this mechanism, other higher-or...

<template name="myTemplate"> {{#each results}} <div><span>{{name}}</span><span>{{age}}</span></div> {{/each}} </template> Template.myTemplate.onCreated(function() { this.results = new ReactiveVar(); Meteor.call('myMethod'...

.gitignore ignores files locally, but it is intended to be committed to the repository and shared with other contributors and users. You can set a global .gitignore, but then all your repositories would share those settings. If you want to ignore certain files in a repository locally and not make t...

There is a metamethod called __call, which defines the bevahiour of the object upon being used as a function, e.g. object(). This can be used to create function objects: -- create the metatable with a __call metamethod local meta = { __call = function(self) self.i = self.i + 1 e...

A common use case for *args in a function definition is to delegate processing to either a wrapped or inherited function. A typical example might be in a class's __init__ method class A(object): def __init__(self, b, c): self.y = b self.z = c class B(A): def __init__(...

You can use a dictionary to assign values to the function's parameters; using parameters name as keys in the dictionary and the value of these arguments bound to each key: def test_func(arg1, arg2, arg3): # Usual function with three arguments print("arg1: %s" % arg1) print("a...