2643 2006-01-05 13:18:30 +0000 [F+O] Conversion from double to float 2006-01-17 16:23:03 +0000 1 1 1 Unclassified XPath / XQuery / XSLT Functions and Operators 1.0 Candidate Recommendation PC Windows XP CLOSED INVALID P2 normal --- 1 mike ashok.malhotra public-qt-comments oldest_to_newest 7622 0 mike 2006-01-05 13:18:30 +0000 In 17.1.3.1 we have blindly copied from XML Schema Part 2 the assertion that the mantissa of a single-precision floating point number is in the range (-2^24+1 to +2^24-1). This is incorrect. It is actually in the range (-2^23+1 to +2^23-1). I have reported this as a bug against XML Schema Part 2: http://www.w3.org/Bugs/Public/show_bug.cgi?id=2642 7639 1 fornaresh 2006-01-05 17:42:37 +0000 (In reply to comment #0) I believe the value space specified for float in XML Schema Part 2 is correct. XML Schema states that "The basic ·value space· of float consists of the values m × 2^e, where m is an integer whose absolute value is less than 2^24, and e is an integer between -149 and 104, inclusive." IEEE754 single-precision floating point representation has 1 sign bit, 8 exponent bits and 23 physical mantissa bits + 1 logical mantissa bit. The logical mantissa bit is always 1 and hence is not stored in the physical representation. But it does result in the absolute value of mantissa being (2^24-1). Similar argument applies to double precision floating point, where there are 52 physical mantissa bit + 1 logical mantissa bit, which results in absolute value of mantissa being (2^53-1). Having argued that the values spaces for float and double in XML Schema are correct, I do agree that the F&O has a typo in the range you point out below. The range should read: (-2^24-1 to +2^24-1), and not (-2^24+1 to +2^24-1) 7857 2 mike 2006-01-17 16:21:39 +0000 Thank you for the clarification. I am withdrawing this comment. Michael Kay