The library-defined partial specializations
of mathematical constant variable templates
are initialized with the nearest representable values of
e,
,
,
π,
,
,
ln2,
ln10,
,
,
,
the Euler-Mascheroni γ constant, and
the golden ratio φ constant ,
respectively.

Pursuant to [namespace.std],
a program may partially or explicitly specialize
a mathematical constant variable template
provided that the specialization depends on a program-defined type.