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List:       musl
Subject:    Re: [musl] [PATCH] Make musl math depend less on libgcc builtins
From:       Sergey Dmitrouk <sdmitrouk () accesssoftek ! com>
Date:       2014-09-18 19:21:35
Message-ID: 20140918192135.GA11968 () zx-spectrum
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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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