Document: WG14 N1501

EPOLE as future direction

Submitter: Fred J. Tydeman (USA)
Submission Date: 2010-06-17
Subject: EPOLE as future direction

C1X, IEEE-754, LIA-2 and LIA-3, and POSIX all make the distinction between domain error, pole error, and range error. All five standards have unique indicators of domain and range errors. But, when it comes to pole errors, things get muddled. IEEE-754 has a specific flag for pole error. The LIA documents have an exceptional value for infinitary. However, C1X and POSIX have the concept of pole error, but no unique errno value for it. This change adds as future direction another errno value for a pole error.

An alternate spelling is ESING (for singularity).

In 7.29 Future library directions, add a new section 7.29.N Mathematics <math.h>:

EPOLE may be used to denote a pole error (also known as singularity or infinitary) via errno.

Add to the Rationale on math.h

errno acquiring the value EPOLE to denote a pole error is a future direction. This will make pole errors distinct from range errors.