Real.fromManExp does not return expected value if man = 0.0

[JohnReppy]

Version

110.99

Operating System

• All
• Linux
• macOS
• Windows
• Other Unix

OS Version

No response

Processor

Any

Component

Basis Library

Severity

Minor

Description of the problem

For any integer exp the expression

Real.fromManExp {man = 0.0, exp = exp}

does not return the expected value. The Basis Library states "If man is +-0, the result is +-0."
https://smlfamily.github.io/Basis/real.html#SIG:REAL.fromManExp:VAL

With 110.85, the expression raises the exception Overflow.

With 110.99, evaluation of the expression does not terminate.

Transcript

No response

Expected Behavior

No response

Steps to Reproduce

Evaluate the expression

  Real.fromManExp {man = 0.0, exp = 0};

with versions 110.99 and 110.85.

Additional Information

No response

Email address

phil.clayton@veonix.com

Comments from smlnj-gforge

Original smlnj-gforge bug number 316

Submitted via web form by Phil Clayton phil.clayton@veonix.com on 2022-07-05 at 13:02:00

Keywords: reals

comment by @JohnReppy on 2022-07-05 15:12:00 +000 UTC

Fixed for 110.99.3 and 2022.1

[pclayton]

I have found other values where Real.fromManExp has similar incorrect behaviour. Did the fix for the issue reported here also fix the following cases?

Real.fromManExp {man = Real.posInf, exp = 0};  (* man = inf *)
Real.fromManExp {man = Real.posInf - Real.posInf, exp = 0};  (* man = nan *)

These cases produce the same result as above:

• With 110.85, the expressions raise the exception Overflow.
• With 110.99, evaluation of the expressions does not terminate.

In these cases, I would expect Real.fromManExp to return man.

[pclayton]

Great to see that SML/NJ has moved to Github! I would have built the source to check for myself but I don't see build instructions so thought it would be quicker just to ask.

[JohnReppy]

I've added instructions to the README for how to build from a repository clone. I also checked the two examples you give and they are both fixed.

[pclayton]

Thanks for the build instructions in the README - the build worked fine. Out of interest, is it necessary to always perform step 2 for subsequent builds? For example, after pulling further commits from a remote branch, can I start at step 3?

[JohnReppy]

You can start at Step 3 (I've added a note to that effect to the README).