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Date: 20 Nov 91 23:59:27 GMT
From: micro-heart-of-gold.mit.edu!wupost!sdd.hp.com!uakari.primate.wisc.edu!use
net.coe.montana.edu!milton!mfeldman@bloom-beacon.mit.edu  (Michael Feldman)
Subject: Re: Red-faced professor gets bitten in search for portability
Message-ID: <1991Nov20.235927.27849@milton.u.washington.edu>
List-Id: <comp.lang.ada>

In article <9111191534.AA20295@ajpo.sei.cmu.edu> ncohen@WATSON.IBM.COM ("Norman
 H. Cohen") writes:
 [ stuff deleted ]
>
>This is one of the primitive functions that the Numerics Rapporteur
>Group of ISO-IEC/JTC1/SC22/WG9 is now working on, with the goal of
>establishing an ISO standard Generic Primitive Functions package.
>(Do not confuse this with the Generic Elementary Functions package,
>which has, if I recall correctly, already been submitted to SC22 as a
>draft standard.  The primitive functions are operations like truncation,
>determining the exponent of a floating-point number, determining the
>mantissa of a floating-point number, and so forth.  They are most
>straightforwardly implemented by dealing directly with the target
>machine's floating-point representation, so compilers are likely to
>treat these functions as intrinsics, replacing calls to them with
>inline code.  The elementary functions are higher-level operations like
>the trig functions, logarithms, and square root, which can be implemented
>portably in terms of the elementary functions.)

This is good. I think it's overdue and hope it happens soon.
>
> > By the way - I am all the more red-faced because I let the dangerous
> > Trunc monster loose into a textbook. 'Course, I haven't run into
> > another Ada text that even discusses the question...
>
>Don't lose sleep over it! I presume (pray) that no safety-critical
>application will incorporate an algorithm from any textbook without
>further careful scrutiny.  Compared to the flub in Dr. Ruth's book
>(incorrectly describing the time of the month at which a woman can
>conceive as the time at which the risk of pregnancy is LOWEST), this is
>no big deal.

Gosh! You mean safety-critical folks don't trust textbooks :-)

I'm red-faced but not insomniac about it. As a fellow author,
you'll understand the "Aarrgghh!" aspect of it. Dr. Ruth's bug was
clearly more serious.

Mike