.TITLE	TRUNC
; AUTHOR:	MARTY PORTNER
;		WORLD BOOK-CHILDCRAFT, INC.
 
;THIS SUBROUTINE TRUNCATES A CHACACTER STRING.
;
;	CALLING FORMAT:
;
;		CALL TRUNC(STRING,POS)
;
; THIS CALL WILL CAUSE STRING TO BE TRUNCATED AT POSITION POS.
;
; DEFAULTS SUPPLIED:		POS<<<<<>>>>> +1
 
	.IDENT	/TRUNC3/
 
	.PSECT	$$STRG,RO,I,CON,LCL
TRUNC::
 
	CMPB	#1,@R5		;ENOUGH ARGS ??
	BLE	1$
	JMP	..BYE		;NO, EXIT
1$:	CMP	#-1,2(R5)	;STRING PRESENT ??
	BEQ	..BYE		;NO, EXIT
	MOV	R0,-(SP)	;SAVE R0
	CMPB	#1,@R5		;
	BEQ	20$		;SUPPLY DEFAULT POS
	CMP	#-1,4(R5)	;POS THERE ??
	BNE	2$		;SUPPLY DEFAULT POS
20$:	MOV	2(R5),R0	;GET ADDR  OF STRING, PLACE IN R0
	CLRB 	(R0)		;ACTS LIKE NULL
	JMP	10$		;
2$:	MOV	2(R5),R0	;
	TST	@4(R5)		;POS O.K. ??
	BLE	10$		;IF NOT, EXIT
	ADD	@4(R5),R0	;CALCULATE TRUNCATION POSITION
	CLRB	-(R0)		;TRUNCATE
10$:	MOV	(SP)+,R0	;
..BYE:	RTS	PC		;RETURN
 
	.END