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Functions in Common Lisp are first class values. An anonymous function can be created by using lambda. For example, here is a function of 3 arguments which we then call using funcall CL-USER> (lambda (a b c) (+ a (* b c))) #<FUNCTION (LAMBDA (A B C)) {10034F484B}> CL-USER> (defvar *fo...

Any symbol in Common Lisp has a slot for a variable to be bound and a separate slot for a function to be bound. Note that the naming in this example is only for illustration. Global variables should not be named foo, but *foo*. The latter notation is a convention to make it clear that the variable ...

Common Lisp contains many higher order functions which are passed functions for arguments and call them. Perhaps the most fundamental are funcall and apply: CL-USER> (list 1 2 3) (1 2 3) CL-USER> (funcall #'list 1 2 3) (1 2 3) CL-USER> (funcall #'list 1 2 3 4 5) (1 2 3 4 5) CL-USER&g...

A very useful feature of Swift 2.2 is having the ability of extending protocols. It works pretty much like abstract classes when regarding a functionality you want to be available in all the classes that implements some protocol (without having to inherit from a base common class). protocol FooPro...

If you are running Docker on OS X or Windows, docker-compose should be included in your Docker for Windows or Docker Toolbox installation. On Linux you can get the latest binaries straight from the GitHub release page: https://github.com/docker/compose/releases You can install the specific releas...

Improper use of pointers are frequently a source of bugs that can include security bugs or program crashes, most often due to segmentation faults. Not checking for allocation failures Memory allocation is not guaranteed to succeed, and may instead return a NULL pointer. Using the returned value, w...

Create a .gitattributes file in the project root containing: * -text This is equivalent to setting core.autocrlf = false.

Create a .gitattributes file in the project root containing: * text=auto This will result in all text files (as identified by Git) being committed with LF, but checked out according to the host operating system default. This is equivalent to the recommended core.autocrlf defaults of: input o...

__construct() is the most common magic method in PHP, because it is used to set up a class when it is initialized. The opposite of the __construct() method is the __destruct() method. This method is called when there are no more references to an object that you created or when you force its deletion...

When contributors add to a project from different machines or operating systems, it may happen that they use different email addresses or names for this, which will fragment contributor lists and statistics. Running git shortlog -sn to get a list of contributors and the number of commits by them co...

A syntactic extension that allows applying the tuple constructor (which is an operator) in a section way: (a,b) == (,) a b -- With TupleSections (a,b) == (,) a b == (a,) b == (,b) a N-tuples It also works for tuples with arity greater than two (,2,) 1 3 == (1,2,3) Mapping This can be u...

This is a type system extension that allows types that are existentially quantified, or, in other words, have type variables that only get instantiated at runtime†. A value of existential type is similar to an abstract-base-class reference in OO languages: you don't know the exact type in contains,...

The following expressions are sequenced: a && b a || b a , b a ? b : c for ( a ; b ; c ) { ... } In all cases, the expression a is fully evaluated and all side effects are applied before either b or c are evaluated. In the fourth case, only one of b or c will be evaluated. In the l...

C11 The following expressions are unsequenced: a + b; a - b; a * b; a / b; a % b; a & b; a | b; In the above examples, the expression a may be evaluated before or after the expression b, b may be evaluated before a, or they may even be intermixed if they correspond to several instruct...

Database transactions ensure that a set of data changes will only be made permanent if every statement is successful. Any query or code failure during a transaction can be caught and you then have the option to roll back the attempted changes. PDO provides simple methods for beginning, committing,...

In this example, documentation for the local function baz (defined in foo.m) can be accessed either by the resulting link in help foo, or directly through help foo>baz. function bar = foo %This is documentation for FOO. % See also foo>baz % This wont be printed, because there is a line w...

On OS X and MacOS, Elixir can be installed via the common package managers: Homebrew $ brew update $ brew install elixir Macports $ sudo port install elixir

In C++, sequences of characters are represented by specializing the std::basic_string class with a native character type. The two major collections defined by the standard library are std::string and std::wstring: std::string is built with elements of type char std::wstring is built with e...

Lists in Elixir are linked lists. This means that each item in a list consists of a value, followed by a pointer to the next item in the list. This is implemented in Elixir using cons cells. Cons cells are simple data structures with a "left" and a "right" value, or a "he...

As seen in "Lambda Functions", functions can take other functions as a parameter. The "function type" which you'll need to declare functions which take other functions is as follows: # Takes no parameters and returns anything () -> Any? # Takes a string and an integer a...