The Dawson integral is defined by \exp(-x^2) \int_0^x dt \exp(t^2). A table of Dawson integral can be found in Abramowitz & Stegun, Table 7.5.
err contains an estimate of the absolute error in the value z.
This function is from the GNU Scientific Library, see http://www.gnu.org/software/gsl/ for documentation.
Package: gsl