wigner3j Module Function

public pure elemental module function wigner3j(dj1, dj2, dj3, dm1, dm2, dm3) result(res)

returns the Wigner 3j symbol via explicit calculation. These should probably be precomputed, but this works for now. The WignerSymbol-f repo seems like a good implementation. The wigner repo by ogorton takes up way too much memory for the high partial waves because it tries to allocate (2N+1)^6 doubles. NOTE: for the high partial wave, we know that we'll only need values with m1 = m2 = m3 = 0, so take advantage of this ?

Arguments

Type	Intent	Optional	Attributes		Name
integer,	intent(in)			::	dj1	twice the angular momenta j
integer,	intent(in)			::	dj2	twice the angular momenta j
integer,	intent(in)			::	dj3	twice the angular momenta j
integer,	intent(in)			::	dm1	twice the angular momenta m
integer,	intent(in)			::	dm2	twice the angular momenta m
integer,	intent(in)			::	dm3	twice the angular momenta m

Return Value real(kind=dp)

the result