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From: Thomas David Rivers <rivers@dignus.com>
Newsgroups: comp.lang.c
Subject: Re: Decimal Floating Point
Date: Mon, 13 Sep 2021 22:23:47 -0400
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Fabian Russell wrote:

>Decimal floating point was standardized as IEEE758-2008 and new C types
>were defined: _Decimal128, _Decimal64, and _Decimal32.
>
>Gcc has many built-in functions (via libgcc) to handle decimal FP:
>
>https://gcc.gnu.org/onlinedocs/gccint/Decimal-float-library-routines.html
>
>However, what puzzles me is that C has not yet incorporated the decimal
>FP types so that the ordinary binary operators, such as "+ - * /" can operate
>directly on them.  Rather, to add two _Decimal_64 values, x, y, for example,
>one must use the function __bid_adddd3(x, y) instead of x + y.
>
>Why bother to include the new types yet now allow them to be used
>arithmetically like all other standard numeric types?
>
>  
>
Just F.Y.I. - the  BID format is suggested by Intel for their processors,
the DPD format is used by IBM in their processors (z/Arch and Power.)
The various standards allow for either... if you dig down in that library
you can also find a function named __dpd_adddd3(x,y) for using the DPD
decimal floating-point format.

We implement those types/operations in the Dignus mainframe C compilers
and take advantage of the native hardware operations (for the DPD format.)

And, you can add two _Decimal64 values with just '+' (and the other
arithmetic operations as well as some I/O operations); it's part of the 
suggested
(not yet adopted) standard.

   - Dave Rivers -


-- 
rivers@dignus.com                        Work: (919) 676-0847
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