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Date: Thu, 18 Sep 2014 22:21:35 +0300
From: Sergey Dmitrouk <sdmitrouk@...esssoftek.com>
To: "musl@...ts.openwall.com" <musl@...ts.openwall.com>
Subject: Re: [PATCH] Make musl math depend less on libgcc builtins
On Thu, Sep 18, 2014 at 10:55:47AM -0700, Szabolcs Nagy wrote:
> i think it is clear: there are tables showing all the predicates
> and to which "traditional names and symbols" they should map.
"EQ" predicate appearing in both 5.1 and 5.2 tables confused me, I
missed that "=" in 5.1 and no "=" in 5.2 means binding to actual
operation.
> table 5.1 shows ==, != as quiet comparisions, table 5.2 shows
> <,> operations as signaling and the text mentions that the quiet
> operations in table 5.3 are for applications which want to
> explicitly handle quiet nans that way
>
> the text in iso C F.3 is not very detailed about the mapping but
> gives hints:
>
> The relational and equality operators provide IEC 60559 comparisons.
> IEC 60559 identifies a need for additional comparison predicates to
> facilitate writing code that accounts for NaNs. The comparison macros
> (isgreater, isgreaterequal, isless, islessequal, islessgreater, and
> isunordered) in <math.h> supplement the language operators to address
> this need. The islessgreater and isunordered macros provide respectively
> a quiet version of the <> predicate and the unordered predicate
> recommended in the Appendix to IEC 60559.
>
> the <,> predicates need a quiet version because the default is not quiet,
> but == and != dont since they are already quiet
>
> the precise mapping will be spelled out in more detail in TS 18661,
> http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1778.pdf
> see "table - 1 operation binding"
> (the latest version seems to be password protected, sigh..)
Thanks for the explanation.
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