Arithmetic expressions

Arithmetic expressions perform operations that involve addition, subtraction, multiplication, division, and modulus.

The following table describes the arithmetic operators and lists them in order of operator precedence from highest to lowest. Unary operators have a higher precedence than binary operators unless parentheses are used to force the evaluation of the binary operator.

Table 1. Arithmetic operators in XQuery
Operator	Purpose	Associativity
-(unary), +(unary)	negates value of operand, maintains value of operand	right-to-left
*, div, idiv, mod	multiplication, division, integer division, modulus	left-to-right
+, -	addition, subtraction	left-to-right
Note: A subtraction operator must be preceded by whitespace if the operator could otherwise be interpreted as part of a previous token. For example, `a-b` is interpreted as a name, but `a - b` and `a -b` are interpreted as arithmetic operations.

The result of an arithmetic expression is a numeric value, an empty sequence, or an error. When an arithmetic expression is evaluated, each operand is atomized (converted into an atomic value), and the following rules are applied:

If the atomized operand is an empty sequence, then the result of the arithmetic expression is an empty sequence.
If the atomized operand is a sequence that contains more than one value, an error is returned.
If the atomized operand is an untyped atomic value (xdt:untypedAtomic), the value is cast to xs:double. If the cast fails, an error is returned.

If the types of the operands, after evaluation, are a valid combination for the arithmetic operator, then the operator is applied to the atomized operands, and the result of this operation is an atomic value or an error (for example, an error might result from dividing by zero.) If the types of the operands are not a valid combination for the arithmetic operator, an error is returned.

Table 2 identifies valid combinations of types for arithmetic operators. In this table, the letter A represents the first operand in the expression, and the letter B represents the second operand. The term numeric denotes the types xs:integer, xs:decimal, xs:float, xs:double, or any types derived from one of these types. If the result type of an operator is listed as numeric, the result type will be the first type in the ordered list (xs:integer, xs:decimal, xs:float, xs:double) into which all operands can be converted by subtype substitution and type promotion.

Table 2. Valid types for operands of arithmetic expressions
Operator with operands	Type of operand A	Type of operand B	Result type
A + B	numeric	numeric	numeric
A + B	xs:date	xdt:yearMonthDuration	xs:date
A + B	xdt:yearMonthDuration	xs:date	xs:date
A + B	xs:date	xdt:dayTimeDuration	xs:date
A + B	xdt:dayTimeDuration	xs:date	xs:date
A + B	xs:time	xdt:dayTimeDuration	xs:time
A + B	xdt:dayTimeDuration	xs:time	xs:time
A + B	xs:dateTime	xdt:yearMonthDuration	xs:dateTime
A + B	xdt:yearMonthDuration	xs:dateTime	xs:dateTime
A + B	xs:dateTime	xdt:dayTimeDuration	xs:dateTime
A + B	xdt:dayTimeDuration	xs:dateTime	xs:dateTime
A + B	xdt:yearMonthDuration	xdt:yearMonthDuration	xdt:yearMonthDuration
A + B	xdt:dayTimeDuration	xdt:dayTimeDuration	xdt:dayTimeDuration
A - B	numeric	numeric	numeric
A - B	xs:date	xs:date	xdt:dayTimeDuration
A - B	xs:date	xdt:yearMonthDuration	xs:date
A - B	xs:date	xdt:dayTimeDuration	xs:date
A - B	xs:time	xs:time	xdt:dayTimeDuration
A - B	xs:time	xdt:dayTimeDuration	xs:time
A - B	xs:dateTime	xs:dateTime	xdt:dayTimeDuration
A - B	xs:dateTime	xdt:yearMonthDuration	xs:dateTime
A - B	xs:dateTime	xdt:dayTimeDuration	xs:dateTime
A - B	xdt:yearMonthDuration	xdt:yearMonthDuration	xdt:yearMonthDuration
A - B	xdt:dayTimeDuration	xdt:dayTimeDuration	xdt:dayTimeDuration
A * B	numeric	numeric	numeric
A * B	xdt:yearMonthDuration	numeric	xdt:yearMonthDuration
A * B	numeric	xdt:yearMonthDuration	xdt:yearMonthDuration
A * B	xdt:dayTimeDuration	numeric	xdt:dayTimeDuration
A * B	numeric	xdt:dayTimeDuration	xdt:dayTimeDuration
A idiv B	numeric	numeric	xs:integer
A div B	numeric	numeric	numeric; but xs:decimal if both operands are xs:integer
A div B	xdt:yearMonthDuration	numeric	xdt:yearMonthDuration
A div B	xdt:dayTimeDuration	numeric	xdt:dayTimeDuration
A div B	xdt:yearMonthDuration	xdt:yearMonthDuration	xs:decimal
A div B	xdt:dayTimeDuration	xdt:dayTimeDuration	xs:decimal
A mod B	numeric	numeric	numeric

Examples

In the following example, the first expression returns the xs:decimal value -1.5, and the second expression returns the xs:integer value -1:
```
-3 div 2
-3 idiv 2
```
In the following expression, the subtraction of two date values results in a value of type xdt:dayTimeDuration:
```
$emp/hiredate - $emp/birthdate
```
The following example illustrates the difference between a subtraction operator and hyphens that are used in the variable names unit-price and unit-discount:
```
$unit-price - $unit-discount 
```