Object-oriented programming is a programming paradigm using "objects" – data structures consisting of data fields and methods together with their interactions – to design applications and computer programs. Programming techniques may include features such as data abstraction,...
Computer programming is the process of designing, writing, testing, debugging, and maintaining the source code of computer programs. This source code is written in one or more programming languages. The purpose of programming is to create a program that performs specific operations or exhibits a...
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
Smalltalk is an object-oriented, dynamically typed, reflective programming language. Smalltalk was created as the language to underpin the "new world" of computing exemplified by "human–computer symbiosis." It was designed and created in part for educational use, more so for constructionist...
NewtonScript is a prototype based programming language created to write programs for the Newton platform. It is heavily influenced by the Self computer language, but modified to be more suited to needs of mobile and embedded devices.- History :...
Prototype-based programming is a style of object-oriented programming in which classes are not present, and behavior reuse is performed via a process of cloning existing objects that serve as prototypes. This model can also be known as classless, prototype-oriented or instance-based programming...
object model similar to the ones in Self and NewtonScript, eliminating the distinction between instance
Object (computer science)
In computer science, an object is any entity that can be manipulated by the commands of a programming language, such as a value, variable, function, or data structure...
In object-oriented programming, a class is a construct that is used as a blueprint to create instances of itself – referred to as class instances, class objects, instance objects or simply objects. A class defines constituent members which enable these class instances to have state and behavior...
. Like Smalltalk, everything is an object and it uses dynamic typing
Type system
A type system associates a type with each computed value. By examining the flow of these values, a type system attempts to ensure or prove that no type errors can occur...
. Like Lisp, programs are just data trees. Io uses actor
Actor model
In computer science, the Actor model is a mathematical model of concurrent computation that treats "actors" as the universal primitives of concurrent digital computation: in response to a message that it receives, an actor can make local decisions, create more actors, send more messages, and...
s for concurrency.
Remarkable features of Io are its minimal size and openness to using external code resources. Io is executed by a small, portable virtual machine
Virtual machine
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
.
History
The language was created by Steve Dekorte around March 7, 2002, after trying to help
a friend, Dru Nelson, with his language, Cel. He found out that he really didn't know much about how languages worked, and set out to write a tiny language to understand the problems better.
Philosophy
Io's goal is to explore conceptual unification and dynamic languages
Dynamic programming language
Dynamic programming language is a term used broadly in computer science to describe a class of high-level programming languages that execute at runtime many common behaviors that other languages might perform during compilation, if at all...
, so the tradeoffs tend to favor simplicity and flexibility over performance.
Object-oriented programming is a programming paradigm using "objects" – data structures consisting of data fields and methods together with their interactions – to design applications and computer programs. Programming techniques may include features such as data abstraction,...
Prototype-based programming is a style of object-oriented programming in which classes are not present, and behavior reuse is performed via a process of cloning existing objects that serve as prototypes. This model can also be known as classless, prototype-oriented or instance-based programming...
Exception handling is a programming language construct or computer hardware mechanism designed to handle the occurrence of exceptions, special conditions that change the normal flow of program execution....
Perl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...
In computing, a regular expression provides a concise and flexible means for "matching" strings of text, such as particular characters, words, or patterns of characters. Abbreviations for "regular expression" include "regex" and "regexp"...
In computer science, garbage collection is a form of automatic memory management. The garbage collector, or just collector, attempts to reclaim garbage, or memory occupied by objects that are no longer in use by the program...
In computer programming, a weak reference is a reference that does not protect the referenced object from collection by a garbage collector . An object referenced only by weak references is considered unreachable and so may be collected at any time...
In computer science, porting is the process of adapting software so that an executable program can be created for a computing environment that is different from the one for which it was originally designed...
In computer science, a library is a collection of resources used to develop software. These may include pre-written code and subroutines, classes, values or type specifications....
Metaprogramming is the writing of computer programs that write or manipulate other programs as their data, or that do part of the work at compile time that would otherwise be done at runtime...
In computer science, the Actor model is a mathematical model of concurrent computation that treats "actors" as the universal primitives of concurrent digital computation: in response to a message that it receives, an actor can make local decisions, create more actors, send more messages, and...
In computer science, concurrency is a property of systems in which several computations are executing simultaneously, and potentially interacting with each other...
Coroutines are computer program components that generalize subroutines to allow multiple entry points for suspending and resuming execution at certain locations...
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
higher-order functions
Syntax
In its simplest form, it is composed of a single identifier:
doStuff
Assuming the above doStuff is a method, it is being called with zero arguments and as a result, explicit parentheses are not required.
If doStuff had arguments, it would look like this:
doStuff(42)
Message passing in computer science is a form of communication used in parallel computing, object-oriented programming, and interprocess communication. In this model, processes or objects can send and receive messages to other processes...
language, and since everything in Io is a message (excluding comment
Comment (computer programming)
In computer programming, a comment is a programming language construct used to embed programmer-readable annotations in the source code of a computer program. Those annotations are potentially significant to programmers but typically ignorable to compilers and interpreters. Comments are usually...
s), each message is sent to a receiver. The above example demonstrates this well, but not fully. To describe this point better, let's look at the next example:
System version
The above example demonstrates message passing in Io; the "version" message is sent to the "System" object.
Programming languages typically support a set of operators: operations which differ from the language's functions in calling syntax and/or argument passing mode. Common examples that differ by syntax are mathematical arithmetic operations, e.g...
are a special case where the syntax is not as cut-and-dried as the above examples. The Io parser intercepts a set of operators defined by the interpreter, and translates them to method calls. For example, the following:
1 + 5 * 8 + 1
translates to:
1 + (5 *(8)) +(1)
As you can see, there is also a little bit of operator precedence happening here, and the precedence levels are the same as with the C precedence levels.
Operators were also turned into method calls. In fact, all operators in Io are methods; the fact that they do not require explicit parentheses is a convenience.
Methods and blocks
In Io there are two ways of creating anonymous functions: methods and blocks. Between them, they are almost identical except for scope
Scope (programming)
In computer programming, scope is an enclosing context where values and expressions are associated. Various programming languages have various types of scopes. The type of scope determines what kind of entities it can contain and how it affects them—or semantics...
. While blocks have lexical scope, methods have dynamic scope.
A "Hello world" program is a computer program that outputs "Hello world" on a display device. Because it is typically one of the simplest programs possible in most programming languages, it is by tradition often used to illustrate to beginners the most basic syntax of a programming language, or to...
In computer science, cloning refers to the making of an exact copy of an object, frequently under the paradigm of instance-based programming, or object-oriented programming.-Shallow copies:...
objects. In Io specifically, a new, empty object is created and only the differences between it and its parent are stored within the new object; this behavior is known as differential inheritance
Differential inheritance
Differential Inheritance is a common inheritance model used by prototype-based programming languages such as JavaScript, Io and NewtonScript. It operates on the principle that most objects are derived from other, more general objects, and only differ in a few small aspects; while usually...
. An example of this behavior is shown:
A := Object clone // creates a new, empty object named "A"
A simple non-recursive factorial function, in Io:
factorial := method(n,
if(n 0, return 1)
res := 1
Range 1 to(n) foreach(i, res = res * i)
)
Because assignment of res * i to res is the last action taken, the function implicitly returns the result and so an explicit return expression is not needed. The above demonstrates the usage of ranges, and doesn't use a for loop, which would be faster.
External links
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