spec_fcts_mod.f90
83b8f38f6c51new_coulomb

spec_fcts_mod.f90
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			module spec_fcts
			!
			! this module contains specfial functions
			!
			! List of functions :

			use prec_const
			private

			public :: Factorial

			contains


			!-------------------------------------------------------!
			real(dp) function Factorial( val ) result( return_value )
			! Evaluates factorial for real positive, and negative half-integer numbers.

			implicit none
			integer :: ival, iloop
			real(dp) :: bval, rval, step
			real(dp), intent(in) :: val

			return_value = 1._dp
			bval = 1.0_dp
			step = sign(1._dp,val)
			rval = step
			ival = abs(nint(val+0.25_dp))
			! If we're dealing with half-integers, recursion relation with sqrt(PI)

			if( modulo(val,1.0_dp) > 0.25_dp ) then
			bval = SQRTPI
			rval = 0.5_dp * rval
			end if
			do iloop = 1, ival
			return_value = return_value * rval
			rval = rval + step
			end do
			if( val < 0._dp ) return_value = 1._dp / return_value
			return_value = return_value * bval

			end function Factorial
			!-------------------------------------------------------!




			end module spec_fcts