*! v 1.2.2 11Nov96. STB-34 sbe13
program define xri_enll
        version 4.0
local ll "`1'"
local M "`2'"
local S "`3'"
if "`4'"=="" { local G $S_gamma }
else local G "`4'"

tempname ln2pi small
scalar `ln2pi'=1.837877
scalar `small'=1e-9

quietly {
	if !$S_cv & !$S_lns {
		local s `S' /* sigma parametrization */
	}
	else {
		tempvar s
		if $S_lns { /* log S parametrization */
			if $S_cv { gen double `s' = `M'*exp(`S') }
			else gen double `s' = exp(`S')
		}
		else gen double `s' = `M'*`S'
	}

* s(igma) is scale factor

	tempvar z Gz
	cap drop __U
	gen double `z' = ($S_mldepn-`M')/`s'
	gen double `Gz' = `G'*`z'
	gen double __U = cond(abs(`Gz')<`small', /*
	 */ (1+0.5*`Gz')*`z', (exp(`Gz')-1)/`G' )
	replace `ll' = -0.5*`ln2pi'-log(`s')-0.5*__U^2+`Gz'
	if $S_trunc {
		replace `ll' = `ll'-log( /*
		 */ cond(`G'<-`small', normprob(-1/`G'), 1 ) /*
		 */ -cond(`G'<`small', 0, normprob(-1/`G') ) )
	}
}
end