XML in a Nutshell, 3rd Edition

Numbers

There are no pure integers in XPath. All numbers are 8-byte, IEEE 754 floating-point doubles, even if they don’t have an explicit decimal point. This format is identical to Java’s double primitive type. In addition to representing floating-point numbers ranging from 4.94065645841246544e-324 to 1.79769313486231570e+308 (positive or negative) and 0, this type includes special representations of positive and negative infinity and a special not a number (NaN) value used as the result of operations like dividing zero by zero.

XPath provides the five basic arithmetic operators that will be familiar to any programmer:

+ Addition

- Subtraction

* Multiplication

div Division

mod Taking the remainder

The more common forward slash couldn’t be used for division because it’s already used to separate location steps in a location path. Consequently, a new operator had to be chosen, div. The word mod was chosen instead of the more common % operator to calculate the remainder. Aside from these minor differences in syntax, all five operators behave exactly as they do in Java. For instance, 2+2 is 4, 6.5 div 1.5 is 4.33333333, 6.5 mod 1.5 is 0.5, and so on. The element <xsl:value-of select="6*7"/> inserts the string 42 into the output tree when the template is instantiated. More often, a stylesheet performs some simple arithmetic on numbers read from the input document. For instance, this template rule calculates the century in which a person was born:

<xsl:template match="person"> <century> <xsl:value-of ...