Exponential power distribution

The exponential power distribution with scale parameter a and exponent b. The distribution is,

$p(x)dx={1 \over 2a\Gamma (1+1/b)}\exp(-|x/a|^{b})dx$

for x >= 0. For b = 1 this reduces to the Laplace distribution. For b = 2 it has the same form as a gaussian distribution, but with $a={\sqrt {2}}\sigma$.