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Re: Decomposing a FLOAT

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On 06/03/2012 04:11 AM, Raj Pashwar wrote:
> On Sat, 02 Jun 2012 14:54:09 -0700, Keith Thompson wrote:
> 
>> Nobody <nobody@nowhere.com> writes:
>>> On Sat, 02 Jun 2012 10:27:20 -0400, James Kuyper wrote:
>>>> I doubt it was a typedef, I think it was just a failure to be
>>>> adequately aware of C's case-sensitivity.
>>>
>>> Or maybe it's just a case of conventional usage of capitals as a form
>>> of emphasis (you can't use boldface in plain text and using HTML on
>>> usenet is frowned upon). In much the same way that posters often use
>>> quotes without necessarily meaning a C string literal.
>>
>> Whatever the OP meant, I hope he understands by now that referring to
>> the type "float" as "FLOAT" is not a good idea.
> 
> Yes, thanks :-)
> 
> In fact John Kupyer was right : on my system FLOAT is a type-def for long 
> double.

John's my brother, and we both spell it Kuyper, not Kupyer. No offense
taken, but a programmer needs to be a bit more careful about details
like that, or the programs won't work. There will, of course, per
tradition, be at least one spelling error in this message, even though I
didn't put one in deliberately. :-}

The example code I provided was based upon the assumption that FLOAT
meant float; that's a perfectly natural assumption, which is why it's a
bad idea to define a typedef with that name; a more neutral name such as
FP_TYPE would be better; a name that indicated the domain of
applicability of the typedef would be even better. For example, one of
third-party libraries I use chose PGS as it's identifying prefix, and
PGSt_integer is their typedef for the integer type to be used when
interfacing with their library.

Since FLOAT was a typedef for long double, the example code I provided
needs modification as follows:

1. Replace float with FLOAT
2. Remove the F suffixes on floating point constants.
3. Replace FLT prefixes on macros from the standard library with LDBL.
4. Replace INFINITY inside decompose_FLOAT() with x/sign.
5a. Replace f suffixes on standard math library functions with l.
or
5b. #include <tgmath.h> and remove the f suffixes from the standard math
library functions.

Note: if there's any chance that FLOAT might be a typedef for a
different type in the future, or on some other platform where this code
needs to work, 4b is to be preferred to 4a. Item 3 needs to be changed
accordingly; but that is relevant only in the test driver.
-- 
James Kuyper

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Thread

Decomposing a FLOAT Raj Pashwar <raj121190@hotmail.NOSPAM.com> - 2012-05-31 20:59 +0000
  Re: Decomposing a FLOAT "Steven G. Kargl" <sgk@REMOVEtroutmask.apl.washington.edu> - 2012-05-31 21:44 +0000
    Re: Decomposing a FLOAT Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-05-31 22:59 +0100
  Re: Decomposing a FLOAT Ike Naar <ike@iceland.freeshell.org> - 2012-05-31 22:04 +0000
  Re: Decomposing a FLOAT James Kuyper <jameskuyper@verizon.net> - 2012-05-31 18:57 -0400
    Re: Decomposing a FLOAT jgk@panix.com (Joe keane) - 2012-06-01 23:02 +0000
      Re: Decomposing a FLOAT Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-01 16:17 -0700
        Re: Decomposing a FLOAT James Kuyper <jameskuyper@verizon.net> - 2012-06-02 10:27 -0400
          Re: Decomposing a FLOAT Nobody <nobody@nowhere.com> - 2012-06-02 20:41 +0100
            Re: Decomposing a FLOAT Keith Thompson <kst-u@mib.org> - 2012-06-02 14:54 -0700
              Re: Decomposing a FLOAT Raj Pashwar <raj121190@hotmail.NOSPAM.com> - 2012-06-03 08:11 +0000
                Re: Decomposing a FLOAT Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-06-03 08:33 -0400
                Re: Decomposing a FLOAT Raj Pashwar <raj121190@hotmail.NOSPAM.com> - 2012-06-03 22:06 +0000
                Re: Decomposing a FLOAT Ian Collins <ian-news@hotmail.com> - 2012-06-04 10:28 +1200
                Re: Decomposing a FLOAT Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-06-03 19:46 -0400
                Re: Decomposing a FLOAT James Kuyper <jameskuyper@verizon.net> - 2012-06-03 08:51 -0400
                Re: Decomposing a FLOAT Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-03 07:48 -0700
                Re: Decomposing a FLOAT James Kuyper <jameskuyper@verizon.net> - 2012-06-03 16:17 -0400
                Re: Decomposing a FLOAT Keith Thompson <kst-u@mib.org> - 2012-06-03 13:43 -0700
                Re: Decomposing a FLOAT Raj Pashwar <raj121190@hotmail.NOSPAM.com> - 2012-06-03 22:06 +0000
                Re: Decomposing a FLOAT Ian Collins <ian-news@hotmail.com> - 2012-06-04 10:30 +1200
                Re: Decomposing a FLOAT James Kuyper <jameskuyper@verizon.net> - 2012-06-03 21:12 -0400
                Re: Decomposing a FLOAT Keith Thompson <kst-u@mib.org> - 2012-06-04 12:20 -0700
                Re: Decomposing a FLOAT Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-05 03:54 -0700
                Re: Decomposing a FLOAT James Kuyper <jameskuyper@verizon.net> - 2012-06-05 08:11 -0400
      Re: Decomposing a FLOAT gazelle@shell.xmission.com (Kenny McCormack) - 2012-06-02 00:03 +0000
        Re: Decomposing a FLOAT jgk@panix.com (Joe keane) - 2012-06-02 00:38 +0000

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