Am 12.02.2014 02:42, schrieb Ralf Quint:
On 2/11/2014 4:53 PM, Martin Frb wrote:
I am trying to figure out the internal representation of these. (So
they can be converted, including conversion form sizes not present in
fpc)
They are all floating point? Pascal has no fixed point?
(nevertheless, rules for fixed point may also be of interest)
dwarf2 says it is specified in each platforms ABI, but I have not
found that (not even found the ABI yet).
Only found:
http://en.wikipedia.org/wiki/Computer_number_format#Representing_fractions_in_binary
And http://www.freepascal.org/docs-html/ref/refsu6.html#x28-310003.1.2
Type Range Significant digits Size
------------------------------------------------------------------------
------------------------------------------------------------------------
------------------------------------------------------------------------
------------------------------------------------------------------------
Real platform dependant ??? 4 or 8
Single 1.5E-45 .. 3.4E38 7-8 4
Double 5.0E-324 .. 1.7E308 15-16 8
Extended 1.9E-4932 .. 1.1E4932 19-20 10
Comp -2E64+1 .. 2E63-1 19-20 8
Currency -922337203685477.5808 .. 922337203685477.5807 19-20 8
apparently there also is real46 (never heard of real16)
The size will actually be in the dwarf, so that I got.
But from that how do I know how many bits are in the exponent? (and
how many in the number). Apparently it depends on the CPU? But where
to get the info?
For all but Real48 (not Real46 or Real16), those are conformant with
IEEE 754 (http://grouper.ieee.org/groups/754/)
Real48 is the non-IEEE754 (predating it) floating point format that
was used in the early Borland Turbo Pascal...
Please not that FPC declares Real48 (aka Real) as "type Double" (in
$fpcdir/rtl/inc/systemh.inc) so it does NOT implement it in a TP
compatible way.
Regards,
Sven
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