IEEE754 is an extension that is located in the ext/misc of the standard
distribution. Of course, before equality testing the numbers must be
"normalized" so they have the same exponent ...
SQLite version 3.9.1 2015-10-22 18:06:40
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database.
sqlite> SELECT
...> (9.2+7.9+0+4.0+2.6+1.3),
...> ieee754(9.2+7.9+0+4.0+2.6+1.3),
...> ieee754(25.0),
...> case when (9.2+7.9+0+4.0+2.6+1.3)=25.0 then "yes" else
"no" end;
25.0|ieee754(7036874417766401,-48)|ieee754(25,0)|no
>>> Decimal(7036874417766401) * Decimal(2**-48)
Decimal('25.00000000000000355271367880')
sqlite> SELECT
...> (9.2+7.8+0+3.0+1.3+1.7),
...> ieee754(9.2+7.8+0+3.0+1.3+1.7),
...> ieee754(23.0),
...> case when (9.2+7.8+0+3.0+1.3+1.7)=23.0 then "yes" else
"no" end;
23.0|ieee754(23,0)|ieee754(23,0)|yes
sqlite> SELECT
...> (9.2+7.9+0+1.0+1.3+1.6),
...> ieee754(9.2+7.9+0+1.0+1.3+1.6),
...> ieee754(21.0),
...> case when (9.2+7.9+0+1.0+1.3+1.6)=21.0 then "yes" else
"no" end;
21.0|ieee754(5910974510923777,-48)|ieee754(21,0)|no
>>> Decimal(5910974510923777) * Decimal(2**-48)
Decimal('21.00000000000000355271367880')
> -----Original Message-----
> From: sqlite-users-bounces at mailinglists.sqlite.org [mailto:sqlite-users-
> bounces at mailinglists.sqlite.org] On Behalf Of Dominique Devienne
> Sent: Friday, 23 October, 2015 08:39
> To: General Discussion of SQLite Database
> Subject: Re: [sqlite] Simple Math Question
>
> On Fri, Oct 23, 2015 at 4:16 PM, Rousselot, Richard A <
> Richard.A.Rousselot at centurylink.com> wrote:
>
> > So I decided to output 1000 digits, because why not? So now I am more
> > perplexed with all these digits showing it is working the opposite of
> how I
> > expected it. Why is the second set of equations evaluating to a "yes"
> when
> > it is the only one that is obviously NOT equal to the expression???
> >
>
> Indeed, that's puzzling :)
>
> To know for sure, you'd need Keith's custom ieee754() function probably.
> Until you can have a look at the actual bits of the computed double, to
> see
> the sign/exponent/mantissa at the binary level, hard to say.
> Could be your use of 1000f too! 15 decimal digits is typical for double.
> --DD
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