From: <peiyongz@ca.ibm.com>

Date: Fri, 1 Mar 2002 18:35:53 -0500

To: xmlschema-dev@w3.org

Message-ID: <OF22863C04.56E57FDA-ON85256B6F.0079AF69@torolab.ibm.com>

Date: Fri, 1 Mar 2002 18:35:53 -0500

To: xmlschema-dev@w3.org

Message-ID: <OF22863C04.56E57FDA-ON85256B6F.0079AF69@torolab.ibm.com>

Hi, there, I'd appreciate it very much, if anyone on the mailing list, can help to clarify some issues we are encountered now. The question applies to double as well. 3.2.4 float [Definition:] float corresponds to the IEEE single-precision 32-bit floating point type [IEEE 754-1985]. 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. In addition to the basic ·value space· described above, the · value space· of float also contains the following special values: positive and negative zero, positive and negative infinity and not-a-number. The ·order-relation· on float is: x < y iff y - x is positive. Positive zero is greater than negative zero. Not-a-number equals itself and is greater than all float values including positive infinity. 3.2.4.1 Lexical representation float values have a lexical representation consisting of a mantissa followed, optionally, by the character "E" or "e", followed by an exponent. The exponent ·must· be an integer. The mantissa must be a decimal number. The representations for exponent and mantissa must follow the lexical rules for integer and decimal. If the "E" or "e" and the following exponent are omitted, an exponent value of 0 is assumed. The special values positive and negative zero, positive and negative infinity and not-a-number have lexical representations 0, -0, INF, -INF and NaN, respectively. The issue: For a datatype like this: <simpleType name="myType"> <restriction base="float"> <minExclusive value="0.0"/> <maxInclusive value="999"/> </restriction> </simpleType> Shall the parser treat the "0.0" as a lexcial representation for a normal zero, or for special value, positive zero? 1. From 3.2.4, we may conclude that we have two value spaces, one is denoted by m × 2^e, and the other which is composed of the five special values, and they are ***disjoint***. 2. From 3.2.4.1, we know that, the value, zero, from the first value space, could have many lexical representations, as long as they conform to the lexical representation of decimal. So we have the production below. [+|-]? [0]+ ['.'[0]+]? which, unfortunately(?) contains the '0' and '-0'. 3. So can we say, A. Any string instance from the production above, except for the '0' and '-0', are either negative zero, nor positive zero, and they are **normal zero**, and we can define the order like this: negative zero < normal zero < positive zero. And that is to say, we have three zeroS, negative zero, normal zero and positive zero. B. Any string instance from the production above, 1. is positive zero, if there is a leading '+' or no leading sign at all, 2. and is negative zero, otherwise. If this is case, we have only two zeroS, negative zero and positive zero, and we **expand** the lexical representation for both negative zero and positive zero. Regards, Peiyong Zhang ____________________________________________ XML Parsers Development, D2-265 IBM Toronto Laboratory , 8200 Warden, Markham Email: peiyongz@ca.ibm.com Phone: (905)413-4088 Fax: (905)413-4854; T/L: 778-4088Received on Friday, 1 March 2002 18:36:02 UTC

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