B.4.2.1. Comparing values of various datatypes
For the first six boolean operators, comparing values of various datatypes is complicated. We explain the various possibilities here:
- If both objects are boolean values
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Then they are equal if they have the same value. For less-than and greater-than comparisons, false is considered less than true (the function call number(false()) returns 0, while number(true()) returns 1).
- If both objects are numbers
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Then the operators work just the way you'd think they would.
- If both objects are strings
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Then they are equal if their Unicode characters are identical. For less-than and greater-than comparisons, the character codes are compared.
- If neither object is a node-set and the operator is = or !=
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Then the two objects are converted to the same object type, and the comparison works as described previously. If one of the objects is a boolean, then the objects are converted to boolean values as if by a call to the boolean() function. If none of the objects are boolean, the next attempted conversion is to a number. If one of the objects is a number, then the objects are converted to numeric values as if by a call to the number() function. Otherwise, all objects are converted to strings as if by a call to the string() function.
- If neither object is a node-set and the operator is <, >, or >=
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Then the objects are converted to numbers and compared.
- If one or both of the objects is a node-set
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Then things really get complicated. If both objects are node-sets, a comparison is true when the string value of at least one node in the first node-set is equal to the string value of at least one node in the second node-set. If one object is a node-set and the other is a number, string, or boolean, the comparison is true when there is at least one node in the node set whose number, string, or boolean value is equal to that number, string, or boolean value.
