.TITLE	NULTST
;
;	SUBROUTINE TO TEST FOR NULL PARAMETERS IN FORTRAN SUBROUTINE
;	THE SUBROUTINE RETURNS -1 IF PARAM IS NULL (.TRUE.)
;		EX.	CALL SUBR(A,,C)
;			SUBROUTINE SUBR(A,B,C)
;			I = NULTST(A)	!I =  0
;			J = NULTST(B)	!J = -1
;			K = NULTST(C)	!K =  0
;
NULTST::	CLR	R0			;0 IF NOT NUL PARAM
	CMP	2(R5),#-1		;IS IT NUL ADDRESS
	BNE	1$			;NO
	DEC	R0			;YES
1$:	RTS	PC
	.END