function Eckerle4(const B: TVec; X: double): double;
begin
  Eckerle4 := B[0]/B[1] * Exp(-0.5*Sqr((X-B[2])/B[1]));
end;

double __fastcall Eckerle4(TVec* const b, double x)
{
  double* B = b->PValues1D(0);

  double sqrterm = (x-B[2])/B[1])*(x-B[2])/B[1]);
  return B[0]/B[1] * Exp(-0.5*(sqrterm));
}