To: J3 07-282r1 From: Michael Ingrassia Subject: Interp F03/0080 Formatted output of a negative real zero value Date: 2007 September 13 The only action taken at meeting #175 was that this interp was accepted as an interp "to be processed". NUMBER: F03/0080 TITLE: Formatted output of a negative real zero value KEYWORDS: formatted output, negative zero, IEEE DEFECT TYPE: ERRATUM STATUS: J3 consideration in progress QUESTION: Suppose a Fortran processor's representation of the real zero value is signed. When a negative real zero value is written using formatted output: (a) Does the Fortran 2003 standard allow the representation of the zero value in the output field to be prefixed with a minus sign? (b) Does the Fortran 2003 standard require the representation of the zero value in the output field to be prefixed with a minus sign? ANSWER: (a) Yes. Although Section 4.4.2 lists some contexts as requiring positive and negative zeros to be treated as equivalent, formatted output is not on that list of contexts. Negative zero can already be produced by formatted output, for example by PRINT '(F4.1)', -0.000001 which in Fortran 95 (but not Fortran 90) is required to write "-0.0" or " -.0". (b) Yes, or Not Necessarily (edits provided for both). The first choice promotes portability. (b1) The negative sign is required to appear in formatted output of a negative zero value. (b2) Negative zero values may be treated as negative values in formatted output at the option of the implementor. DISCUSSION: A negative zero value is negative by name but zero by nature. Therefore a context which refers to negative values must always be inspected to see if it is appropriate to also include negative zero values, and the instance in 10.6.1 needs amendment. EDITS: For (b1): [227:3-4] Change from The representation of a negative internal value in the field shall be prefixed with a minus sign. to The representation of a negative internal value or a negative zero value in the field shall be prefixed with a minus sign. For (b2): [227:4] Add the sentence The representation of a negative zero value in the field may be prefixed with a minus sign. SUBMITTED BY: Michael Ingrassia HISTORY: 06-126 m175 F03/0080 Submitted 07-282r1 m182