구차니의 잡동사니 모음

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

The function computes the effective boolean value of a sequence, defined according to the following rules. See also Section 2.4.3 Effective Boolean Value XP31.

• If $arg is the empty sequence, fn:boolean returns false.

• If $arg is a sequence whose first item is a node, fn:boolean returns true.

• If $arg is a singleton value of type xs:boolean or a derived from xs:boolean, fn:boolean returns $arg.

• If $arg is a singleton value of type xs:string or a type derived from xs:string, xs:anyURI or a type derived from xs:anyURI, or xs:untypedAtomic, fn:boolean returns false if the operand value has zero length; otherwise it returns true.

• If $arg is a singleton value of any numeric type or a type derived from a numeric type, fn:boolean returns false if the operand value is NaN or is numerically equal to zero; otherwise it returns true.