[math.constants]

The library-defined partial specializations of mathematical constant variable templates are initialized with the nearest representable values of e,

log {2 e, log {10 e, π, \frac{1 π, \frac{1 \sqrt{π, ln 2, ln 10, \sqrt{2, \sqrt{}}}}{\sqrt{π, ln 2, ln 10, \sqrt{2, \sqrt{,}}}}}{π}}_{10 e, π, \frac{1 π, \frac{1 \sqrt{π, ln 2, ln 10, \sqrt{2, \sqrt{,}}}}{\sqrt{π, ln 2, ln 10, \sqrt{2, \sqrt{,}}}}}{π}}}_{2 e, log {10 e, π, \frac{1 π, \frac{1 \sqrt{π, ln 2, ln 10, \sqrt{2, \sqrt{,}}}}{\sqrt{π, ln 2, ln 10, \sqrt{2, \sqrt{,}}}}}{π}}_{10 e, π, \frac{1 π, \frac{1 \sqrt{π, ln 2, ln 10, \sqrt{2, \sqrt{,}}}}{\sqrt{π, ln 2, ln 10, \sqrt{2, \sqrt{3,}}}}}{π}}}

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.

A program that instantiates a primary template of a mathematical constant variable template is ill-formed.