Submitter: Fred J. Tydeman
Submission Date: 2013-08-20
Related:DR 285

Summary

What is the value of: `_Bool b = 0.0 + 3.0*I;`

I believe that there is a contradiction between 6.3.1.2 Boolean type and 6.3.1.7 Real and complex in that one requires that the value to be 1 and the other requires the value to be 0.

6.3.1.2 Boolean type

1 When any scalar value is converted to _Bool, the result is 0 if the value compares equal to 0; otherwise, the result is 1.

6.3.1.7 Real and complex

2 When a value of complex type is converted to a real type, the imaginary part of the complex value is discarded and the value of the real part is converted according to the conversion rules for the corresponding real type.

DR 285 against C99 had a similar issue on conversion from imaginary to boolean. That resulted in:

G.4.2 Real and imaginary

1 When a value of imaginary type is converted to a real type other than _Bool,376) the result is a positive zero.

376) See 6.3.1.2.

Suggested Technical Corrigendum

I believe that 6.3.1.7 Real and complex, paragraph 2 should be changed to:

2 When a value of complex type is converted to a real type other than _Bool(footnote), the imaginary part of the complex value is discarded and the value of the real part is converted according to the conversion rules for the corresponding real type.

(footnote) See 6.3.1.2.