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### Arity

The **arity** is the number of arguments or operands taken by a function or operation.

##### Explanation

This number is expressed by names as:

• | NullaryA constant is an operation of arity 0. |

• | UnaryThe plus sign and the minus sign are operations of arity 1. |

• | BinaryAn addition, a subtraction, a multiplication and a division are operations of arity 2. |

• | TernaryA ternary operator takes three operands. |

• | n-aryAn n-ary operator takes n operands. |

• | Varying aryA function can accept a variable number of arguments. |

##### Example 0

The nullary function *f* () or the operation time have no argument. The instruction STOP has no operand.

##### Example 1

The unary function *f* (*x*) has the variable *x* as argument. The operation +1 has only one operand.

##### Example 2

The binary function *f* (*x, y*) has the two variables *x* and *y* as argument. The operation *x* + *y* has 2 operands.

##### Example 3

The ternary function *f* (*x, y, z*) has the three variables *x*, *y* and *z* as argument.

##### Example 4

The *n*-ary function *f* (*x*_{1}, *x*_{2}, . . . , *x _{n}*) has

*n*variables as argument.

##### Example 5

The varying ary function with the variable *x* as argument is written as

The number *m* is the lower bound of the summation, the number *n* is its upper bound.