[Cfp-interest] CFP binary FP

[Fred J. Tydeman]

On Fri, 09 Dec 2011 09:15:25 -0800 Jim Thomas wrote:
>>7.12.6.7: Not happy with "domain error or range error"
>> 
>I used the same words as for ilogb in C1x.

I understand.  But, I am very unhappy with those words.  It makes a mess.

Here are the words that I think should be used:

If x is zero, a domain error occurs and they compute the value of
FP_LLOGB0;

if x is infinite, a domain error occurs and they compute the value
LONG_MAX;

if x is a NaN, a domain error occurs and they compute the value
FP_LLOGBNAN;

...

If the correct value is outside the range of the return type, a domain
error occurs and the numeric result is unspecified.

OR

A domain error occurs is x is zero, infinite, or NaN.
If the correct value is outside the range of the return type, a domain
error occurs and the numeric result is unspecified.

>>Typo:  Page 14: 7.12.14.6: "... the square (as if)..."
>>How get range error for fsqrt?
>> 
>fsqrt(DBL_MAX), for example

I think not.  The exponent of the sqrt is 1/2 of the exponent of
the argument.  So, overflow or underflow cannot happen.

>>ISSUE:  If fesetexcept() cannot cause a trap, do we need to add words 
>>to feraiseexcpet() that it can cause a trap?
>>Do we need to add words that flags have 3 states:
>>clear
>>raised (causing a trap)
>>set (not causing a trap)
>>
>> 
>raise and set (using C terminology) put the flags in the same state. 
>The difference is that raise may cause side effects, namely traps.

Then, there should be words about these side effects.
Also, does the order of raising and enabling a trap matter?
Or, are those words going to happen in part 5 (which I assume
is the part that will discuss trapping (alternate exceptions))?

---
Fred J. Tydeman        Tydeman Consulting
tydeman at tybor.com      Testing, numerics, programming
+1 (775) 358-9748      Vice-chair of PL22.11 (ANSI "C")
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