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Calling Number Functions
This section describes the number functions that you can call in a query. The operations you can perform are
Converting an Object to a Number
In some situations, you might want to force a numeric comparison. The XPath processor performs a numeric comparison if either operand is numeric and neither is Boolean. (If one operand is Boolean, the XPath processor converts the other to Boolean and performs a Boolean comparison.) However, if neither operand is a numeric or Boolean value, you can call the number() function on one operand to convert it to a numeric value. The XPath processor automatically converts the other operand to a numeric value.
To perform a numeric comparison, you must call the number() function to convert a Boolean operand, if there is one, to a numeric value.
The format of the number() function is
If you omit the argument, the value of the argument defaults to a node set with the context node as its only member. Table 98 shows how the number() function converts its argument to a number:
Argument
|
Converted Value
|
|---|
String that consists of optional white space followed by an optional minus sign followed by a number followed by white space
|
IEEE 754 number that is nearest to the mathematical value represented by the string.
|
Any other string
|
NaN (not a number)
|
Boolean true |
1
|
Boolean false |
0
|
Node set
|
First the XPath processor converts the node set to a concatenated string as if by a call to the string() function for the first node in the node set, in document order. The XPath processor then converts this string the same way as it would a string argument.
|
Table 98. number() Function Arguments and Converted Values
Obtaining the Sum of the Values in a Node Set
To obtain the sum of the values of the nodes in a set, call the sum() function. The format is
For each node in the argument node-set, the XPath processor converts the string value of the node to a number. The sum() function returns the sum of these numbers.
Obtaining the Largest, Smallest, or Closest Number
To obtain the largest integer that is not greater than a particular number, call the floor() function. The format is
The floor() function returns the largest (closest to positive infinity) number that is not greater than the argument and that is an integer. For example:
floor(5.3) returns 5floor(-5.3) returns -6
To obtain the smallest integer that is not less than a particular number, call the ceiling() function. The format is
The ceiling() function returns the smallest (closest to negative infinity) number that is not less than the argument and that is an integer. For example:
ceiling(5.3) returns 6ceiling(-5.3) returns -5
To obtain the closest integer to a particular number, call the round() function. The format is
The round() function returns the number that is closest to the argument and that is an integer. If there are two such numbers, the function returns the one that is closest to positive infinity. For example:
round(5.3) returns 5round(5.6) returns 6round(5.5) returns 6
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