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CMUCL also has an extension to support double-double-float
type. This float format provides extended precision of about 31
decimal digits, with the same exponent range as double-float
.
It is completely integrated into CMUCL, and can be used just like
any other floating-point object, including arrays, complex
double-double-float
’s, and special functions. With appropriate
declarations, no boxing is needed, just like single-float
and
double-float
.
The exponent marker for a double-double float number is “W”, so “1.234w0” is a double-double float number.
Note that there are a few shortcomings with
double-double-float
’s:
most-positive-double-float
,
double-float-positive-infinity
, etc. This is because
these are not really well defined for double-double-float
’s.
double-double-float
’s are implemented.
double-double-float
arithmetic is quite a bit slower
than double-float
since there is no hardware support for
this type.
pi
is still a double-float
instead
of a double-double-float
. Use ext:dd-pi
if you
want a double-double-float
value for \pi.
The double-double-float
type. It is in the EXTENSIONS
package.
A double-double-float
approximation to \pi.
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