Interpretations

Answering questions that may arise related to the meaning of portions of an IEEE standard concerning specific applications.

IEEE Standards Interpretations for IEEE Std 1003.2™-1992 IEEE Standard for Information Technology--Portable Operating System Interfaces (POSIX®)--Part 2: Shell and Utilities

Copyright © 1996 by the Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue New York, New York 10016-5997 USA All Rights Reserved.

Interpretations are issued to explain and clarify the intent of a standard and do not constitute an alteration to the original standard. In addition, interpretations are not intended to supply consulting information. Permission is hereby granted to download and print one copy of this document. Individuals seeking permission to reproduce and/or distribute this document in its entirety or portions of this document must contact the IEEE Standards Department for the appropriate license. Use of the information contained in this document is at your own risk.

IEEE Standards Department, Copyrights and Permissions, 445 Hoes Lane, Piscataway, New Jersey 08855-1331, USA

Interpretation Request #77
Topic: bc - scale Relevant Clauses: 4.3.7.1

POSIX.2 Subclause 4.3 specifies the semantics of the Óbc" utility. In subclause 4.3.7.1, lines 1570-1571 state: The scale of an invocation of each of these functions shall be the scale of the value of the scale register when the function is invoked. The functions referred to are the math functions s(), c(), a(), l(), e() and j(). Suppose that bc is invoked with the -l flag, and that the scale is 20. What is the value of the expression scale(a(0)) On the one hand, the sentence quoted above implies that it should be 20. On the other hand, the value of a(0) is exactly 0, and the scale of 0 is 0.

Interpretation Response
The specification on lines 1570-1573, page 196 is talking about the scale used while computing the value of the arctangent, not about the computed arctangent, since arctangent (0) is zero, scale(a(0)) is equivalent to scale(0) which is zero. The standard clearly states the behaviour for bc and scale(), and conforming implementations must conform to this.

Rationale for Interpretation
None.