;+
; function vsign(x)
; 
; returns total sign of x
;
; Method: counts number of negatives.
;         returns -1 if odd, +1 if even, 0 if all x are zero
;
; Fergus Gallagher, RSADU
;-
function vsign,x
	dummy = where(x lt 0,minus)
	dummy = where(x gt 0,plus)
	if (plus+minus) eq 0 then return,0 ; all  zero
	v = (minus mod 2)
	u = 1-2*(v eq 1)
	return,u
end

;+
; function mtotal(x)
;
; Calculates fast geometric product of a vector x.
;
; Method:   ans = exp(total(ln(x))).
;
; Copes with the case if any x negative.
;
; Fergus Gallagher, RSADU.
; Modified to cope with zero elements, D P Steele, ISR.
;
;-
function mtotal,x
	y = abs(double(x))
	IF MIN(y) GT 0 THEN BEGIN
	    a = exp(total(alog(y)))*vsign(x)
	    return,a
	    ENDIF ELSE RETURN,0
end