Arity
sorry
- no such article on GetWiki
- import not available from Pseudopedia
In
logic,
mathematics, and
computer science, the
arity {{IPAc-en|audio=en-us-arity.ogg|ˈ|ɛ|r|ɨ|t|i}} of a
function or
operation is the number of
arguments or
operands the function or operation accepts. The arity of a
relation (or
predicate) is the dimension of the domain in the corresponding
Cartesian product. (A function of arity
n thus has arity
n+1 considered as a relation.) The term springs from words like unary, binary, ternary, etc. Unary functions or predicates may be also called "monadic"; similarly, binary functions may be called "dyadic". In mathematics, depending on the branch, arity may be named
type{{cn|date=November 2012}} or
rank.
(1)(2) (These two words can have many other meanings in mathematics though.) In logic and philosophy, arity is also called
adicity and
degree.
(3)(4) In
linguistics, arity is usually named
valency.
(5)In
computer programming, there is often a
syntactical distinction between
operators and
functions; syntactical operators usually have arity 0, 1, or 2. Functions vary widely in the number of arguments, though large numbers can become unwieldy. Some programming languages also offer support for
variadic functions, i.e. functions syntactically accepting a variable number of arguments.
Examples
{{Expand section|more math and logic examples|date=March 2012}}The term "arity" is rarely employed in everyday usage. For example, rather than saying "the arity of the
addition operation is 2" or "addition is an operation of arity 2" one usually says "addition is a binary operation".In general, the naming of functions or operators with a given arity follows a convention similar to the one used for
n-based
numeral systems such as
binary and
hexadecimal. One combines a
Latin prefix with the -ary ending; for example:
Nullary
Sometimes it is useful to consider a
constant to be an operation of arity 0, and hence call it
nullary.Also, in non-
functional programming, a function without arguments can be meaningful and not necessarily constant (due to
side effects). Often, such functions have in fact some
hidden input which might be
global variables, including the whole state of the system (time, free memory, ...). The latter are important examples which usually also exist in "purely" functional programming languages.
Unary
Examples of
unary operators in mathematics and in programming include the unary minus and plus, the increment and decrement operators in
C-style languages (not in logical languages), and the
factorial,
reciprocal,
floor,
ceiling,
fractional part,
sign,
absolute value,
complex conjugate, and
norm functions in mathematics. The
two's complement,
address reference and the
logical NOT operators are examples of unary operators in math and programming. According to
Quine, a more suitable term is "singulary".
[{{Citation
]
| last = Quine
| first = W. V. O.
| title = Mathematical logic
| year = 1940
| place = Cambridge, MA
| publisher = Harvard University Press
| page=13
}}
All functions in lambda calculus and in some functional programming languages (especially those descended from ML) are technically unary, but see n-ary below.Binary
Most operators encountered in programming are of the binary form. For both programming and mathematics these can be the multiplication operator, the addition operator, the division operator. Logical predicates such as OR, XOR, AND, IMP are typically used as binary operators with two distinct operands.Ternary
From C, C++, C#, Java, Perl and variants comes the ternary operator (?:), which is a so-called conditional operator, taking three parameters.Forth also contains a ternary operator, */, which multiplies the first two (one-cell) numbers, dividing by the third, with the intermediate result being a double cell number. This is used when the intermediate result would overflow a single cell.Python has a ternary conditional statement, x if C else y.The dc calculator has several ternary operators, such as |, which will pop three values from the stack and efficiently compute xy mod z
with arbitrary precision.Additionally, many assembly language instructions are ternary or higher, such as MOV %AX, (%BX,%CX), which will load (MOV) into register AX the contents of a calculated memory location that is the sum (parenthesis) of the registers BX and CX.n-ary
From a mathematical point of view, a function of n arguments can always be considered as a function of one single argument which is an element of some product space. However, it may be convenient for notation to consider n-ary functions, as for example multilinear maps (which are not linear maps on the product space, if n≠1).The same is true for programming languages, where functions taking several arguments could always be defined as functions taking a single argument of some composite type such as a tuple, or in languages with higher-order functions, by currying. Variable arity
In computer science, a function accepting a variable number of arguments is called variadic. In logic and philosophy, predicates or relations accepting a variable number of arguments are called multigrade, anadic, or variably polyadic.(6)Other names
- Nullary means 0-ary.
- Unary means 1-ary.
- Binary means 2-ary.
- Ternary means 3-ary.
- Quaternary means 4-ary.
- Quinary means 5-ary.
- Senary means 6-ary.
- Septenary means 7-ary.
- Octary means 8-ary.
- Nonary means 9-ary.
- Polyadic, multary and multiary mean 2 or more operands (or parameters).
- n-ary means n operands (or parameters), but is often used as a synonym of "polyadic".
An alternative nomenclature is derived in a similar fashion from the corresponding Greek roots; for example, niladic (or medadic), monadic, dyadic, triadic, polyadic, and so on. Thence derive the alternative terms adicity and adinity for the Latin-derived arity.These words are often used to describe anything related to that number (e.g., undenary chess is a chess variant with an 11×11 board, or the Millenary Petition of 1603).See also
References
-
[BOOK, Michiel Hazewinkel, Encyclopaedia of Mathematics, Supplement III,weblink 2001, Springer, 978-1-4020-0198-7, 3, ]
-
[BOOK, Eric Schechter, Handbook of Analysis and Its Foundations,weblink 1997, Academic Press, 978-0-12-622760-4, 356, ]
-
[BOOK, Michael Detlefsen, David Charles McCarty, John B. Bacon, Logic from A to Z,weblink 1999, Routeledge, 978-0-415-21375-2, 7, ]
-
[BOOK, Nino B. Cocchiarella, Max A. Freund, Modal Logic: An Introduction to its Syntax and Semantics,weblink 2008, Oxford University Press, 978-0-19-536658-7, 121, ]
-
[BOOK, David Crystal, Dictionary of Linguistics and Phonetics, 2008, John Wiley & Sons, 978-1-405-15296-9, 507, 6th, ]
-
[JOURNAL, 10.1093/mind/113.452.609, Oliver, Alex, 2004, Multigrade Predicates, Mind, 113, 609–681, ]
External links
A monograph available free online:
Operace (matematika)#Arita operace
