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XPath function: boolean boolean (object)

Standard excerpt:

The boolean function converts its argument to a boolean as follows: a number is true if and only if it is neither positive or negative zero nor NaN, a node-set is true if and only if it is non-empty, a string is true if and only if its length is non-zero an object of a type other than the four basic types is converted to a boolean in a way that is dependent on that type Examples (xslt:xml): Overview

Interactive xlab: [number functions] [xsl:value-of] [xsl:template]