Usage
fermi_dirac_m1(x, give=FALSE, strict=TRUE)
fermi_dirac_0(x, give=FALSE, strict=TRUE)
fermi_dirac_1(x, give=FALSE, strict=TRUE)
fermi_dirac_2(x, give=FALSE, strict=TRUE)
fermi_dirac_int(j, x, give=FALSE, strict=TRUE)
fermi_dirac_mhalf(x, give=FALSE, strict=TRUE)
fermi_dirac_half(x, give=FALSE, strict=TRUE)
fermi_dirac_3half(x, give=FALSE, strict=TRUE)
fermi_dirac_inc_0(x, b, give=FALSE, strict=TRUE)