*! version 1.0.0  10aug1996
program define bipr_lf
	version 5.0
	local ll  "`1'"  /* Log l */
	local xb1 "`2'"  /* x1*b1 */
	local xb2 "`3'"  /* x2*b2 */
	local rr  "`4'"  /* rho */

	quietly {
		replace `ll' = binorm(`xb1',`xb2',`rr')   /*
			*/ if $S_y1==1 & $S_y2==1
		replace `ll' = binorm(-`xb1',`xb2',-`rr') /*
			*/ if $S_y1==0 & $S_y2==1
		replace `ll' = normprob(-`xb2')  if $S_y2==0
		replace `ll'=log(`ll')
	}
end