object-oriented programming
Object-oriented programming (OOP) is a programming paradigm based on the concept of " objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of ...
language
Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of ...
inspired by
Smalltalk
Smalltalk is an object-oriented, dynamically typed reflective programming language. It was designed and created in part for educational use, specifically for constructionist learning, at the Learning Research Group (LRG) of Xerox PARC by ...
,
Self
The self is an individual as the object of that individual’s own reflective consciousness. Since the ''self'' is a reference by a subject to the same subject, this reference is necessarily subjective. The sense of having a self—or ''selfhood ...
,
Lua
Lua or LUA may refer to:
Science and technology
* Lua (programming language)
* Latvia University of Agriculture
* Last universal ancestor, in evolution
Ethnicity and language
* Lua people, of Laos
* Lawa people, of Thailand sometimes referred t ...
,
Lisp
A lisp is a speech impairment in which a person misarticulates sibilants (, , , , , , , ). These misarticulations often result in unclear speech.
Types
* A frontal lisp occurs when the tongue is placed anterior to the target. Interdental lispi ...
NewtonScript
NewtonScript is a prototype-based programming language created to write programs for the Newton platform. It is heavily influenced by the Self programming language, but modified to be more suited to needs of mobile and embedded devices.
Hist ...
.Io Programming Guide /ref> Io has a prototype-based object model similar to the ones in Self and NewtonScript, eliminating the distinction between
instance
Instantiation or instance may refer to:
Philosophy
* A modern concept similar to ''participation'' in classical Platonism; see the Theory of Forms
* The instantiation principle, the idea that in order for a property to exist, it must be had by ...
and
class
Class or The Class may refer to:
Common uses not otherwise categorized
* Class (biology), a taxonomic rank
* Class (knowledge representation), a collection of individuals or objects
* Class (philosophy), an analytical concept used differently ...
. Like Smalltalk, everything is an object and it uses
dynamic typing
In computer programming, a type system is a logical system comprising a set of rules that assigns a property called a type to every "term" (a word, phrase, or other set of symbols). Usually the terms are various constructs of a computer progra ...
. Like Lisp, programs are just data trees. Io uses
actor
An actor or actress is a person who portrays a character in a performance. The actor performs "in the flesh" in the traditional medium of the theatre or in modern media such as film, radio, and television. The analogous Greek term is (), l ...
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
In computing, a virtual machine (VM) is the virtualization/ emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized har ...
.
History
The language was created by Steve Dekorte in 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, so the tradeoffs tend to favor simplicity and flexibility over performance.
Features
* Pure
object-oriented
Object-oriented programming (OOP) is a programming paradigm based on the concept of " objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of ...
based on
prototypes
A prototype is an early sample, model, or release of a product built to test a concept or process. It is a term used in a variety of contexts, including semantics, design, electronics, and software programming. A prototype is generally used t ...
* Code-as-data /
homoiconic
In computer programming, homoiconicity (from the Greek words ''homo-'' meaning "the same" and ''icon'' meaning "representation") is a property of some programming languages. A language is homoiconic if a program written in it can be manipulated as ...
*
Lazy evaluation
In programming language theory, lazy evaluation, or call-by-need, is an evaluation strategy which delays the evaluation of an expression until its value is needed ( non-strict evaluation) and which also avoids repeated evaluations ( sharing).
T ...
of function parameters
*
Higher-order functions
In mathematics and computer science, a higher-order function (HOF) is a function that does at least one of the following:
* takes one or more functions as arguments (i.e. a procedural parameter, which is a parameter of a procedure that is itse ...
*
Introspection
Introspection is the examination of one's own Consciousness, conscious thoughts and feelings. In psychology, the process of introspection relies on the observation of one's Mental representation, mental state, while in a Spirituality, spiritual c ...
metaprogramming
Metaprogramming is a programming technique in which computer programs have the ability to treat other programs as their data. It means that a program can be designed to read, generate, analyze or transform other programs, and even modify itself ...
concurrency
Concurrent means happening at the same time. Concurrency, concurrent, or concurrence may refer to:
Law
* Concurrence, in jurisprudence, the need to prove both ''actus reus'' and ''mens rea''
* Concurring opinion (also called a "concurrence"), a ...
*
Coroutine
Coroutines are computer program components that generalize subroutines for non-preemptive multitasking, by allowing execution to be suspended and resumed. Coroutines are well-suited for implementing familiar program components such as cooperative ...
s
*
Exception handling
In computing and computer programming, exception handling is the process of responding to the occurrence of ''exceptions'' – anomalous or exceptional conditions requiring special processing – during the execution of a program. In general, a ...
portable
Portable may refer to:
General
* Portable building, a manufactured structure that is built off site and moved in upon completion of site and utility work
* Portable classroom, a temporary building installed on the grounds of a school to provide a ...
shared library
In computer science, a library is a collection of non-volatile memory, non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, Code r ...
dynamic loading on most platforms
* Small
virtual machine
In computing, a virtual machine (VM) is the virtualization/ emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized har ...
Syntax
In its simplest form, it is composed of a single identifier:
doStuff
Assuming the above doStuff is a
method
Method ( grc, μέθοδος, methodos) literally means a pursuit of knowledge, investigation, mode of prosecuting such inquiry, or system. In recent centuries it more often means a prescribed process for completing a task. It may refer to:
*Scien ...
, 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)
Io is a
message passing
In computer science, message passing is a technique for invoking behavior (i.e., running a program) on a computer. The invoking program sends a message to a process (which may be an actor or object) and relies on that process and its supporti ...
language, and since everything in Io is a message (excluding
comment
Comment may refer to:
* Comment (linguistics) or rheme, that which is said about the topic (theme) of a sentence
* Bernard Comment (born 1960), Swiss writer and publisher
Computing
* Comment (computer programming), explanatory text or informat ...
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.
Operators
Operator may refer to:
Mathematics
* A symbol indicating a mathematical operation
* Logical operator or logical connective in mathematical logic
* Operator (mathematics), mapping that acts on elements of a space to produce elements of another sp ...
are a special case where the syntax is not as cut-and-dried as the above examples. The Io
parser
Parsing, syntax analysis, or syntactic analysis is the process of analyzing a string of symbols, either in natural language, computer languages or data structures, conforming to the rules of a formal grammar. The term ''parsing'' comes from Lati ...
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)
All operators in Io are methods; the fact that they do not require explicit parentheses is a convenience. As you can see, there is also a little bit of
operator precedence
In mathematics and computer programming, the order of operations (or operator precedence) is a collection of rules that reflect conventions about which procedures to perform first in order to evaluate a given mathematical expression.
For exam ...
happening here, and the precedence levels are the same as with the C precedence levels.
Methods and blocks
In Io there are two ways of creating
anonymous function
In computer programming, an anonymous function (function literal, lambda abstraction, lambda function, lambda expression or block) is a function definition that is not bound to an identifier. Anonymous functions are often arguments being passed t ...
s: methods and blocks. Between them, they are almost identical except for
scope
Scope or scopes may refer to:
People with the surname
* Jamie Scope (born 1986), English footballer
* John T. Scopes (1900–1970), central figure in the Scopes Trial regarding the teaching of evolution
Arts, media, and entertainment
* CinemaS ...
. While blocks have
lexical scope
In computer programming, the scope of a name binding (an association of a name to an entity, such as a variable) is the part of a program where the name binding is valid; that is, where the name can be used to refer to the entity. In other part ...
, methods have
dynamic scope
In computer programming, the scope of a name binding (an association of a name to an entity, such as a variable) is the part of a program where the name binding is valid; that is, where the name can be used to refer to the entity. In other parts ...
.
Both ''method'' and ''block'' are
higher-order functions
In mathematics and computer science, a higher-order function (HOF) is a function that does at least one of the following:
* takes one or more functions as arguments (i.e. a procedural parameter, which is a parameter of a procedure that is itse ...
.
Examples
The ubiquitous
Hello world program
''Hello'' is a salutation or greeting in the English language. It is first attested in writing from 1826. Early uses
''Hello'', with that spelling, was used in publications in the U.S. as early as the 18 October 1826 edition of the '' Norwich ...
:
"Hello, world!" println
New objects are created by
cloning
Cloning is the process of producing individual organisms with identical or virtually identical DNA, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction. In the field of biotechnology, c ...
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 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 dif ...
. 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
In the Hebrew Bible and in the Old Testament, the word ranges has two very different meanings.
Leviticus
In Leviticus 11:35, ranges probably means a cooking furnace for two or more pots, as the Hebrew word here is in the dual number; or perhaps ...
, and doesn't use a for() loop, which would be faster.
See also
*
Ioke (programming language) Ioke is the Hawaiian language equivalent for the name Joyce (name) Joyce is an Irish and French given name and surname. It is derived from the Old French masculine name ''Josse'', which derived from the Latin name ''Iudocus'', the Latinized form o ...