_impl and _e -- what is the Difference?

[Alexei V. Meremianin]

  Hello,

I could not find in infos, what is the difference between these
 functions

 - Function: int gsl_sf_dawson_impl (double x, gsl_sf_result * result)
 - Function: int gsl_sf_dawson_e (double x, gsl_sf_result * result)
     Exceptional Return Values: GSL_EUNDRFLW
 
 It is written that _e mean "with error status", but 
 _impl also returns gsl_sf_result with such the status?
It is mysterious thing... 

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    Alexei Meremianin,	       |Phones: home (0732)131528
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