úή1 "Error function related functions. The derivative of  is  x -> 2 / sqrt pi * exp (x^2),  and this uniquely determines  by  erf 0 = 0. Minimal complete definition is  or .  erfc x = 1 - erf x erfcx x = exp (x*x) * erfc x normcdf x = erfc(-x  sqrt 2)  2   erf-1.0.0.0Data.Number.ErfErferferfcerfcxnormcdfc_erfcfc_erffc_erfcc_erf