BISTRS.ASM

; [ This translation created 10-Feb-83 by Version 4.3 ]

	.RADIX  8		; To be safe

CSEG	SEGMENT PUBLIC 'CODESG' 
	ASSUME  CS:CSEG

INCLUDE	OEM.H

	TITLE   BISTRS  BASIC Interpreter String  routines/WHG/PGA etc.

	.RADIX	10

TSHIBA=0
PC8A=0
ZENITH=0
ALPCPM=0
CAN8=0
TRSHHC=0
NECPPC=0

DSEG	SEGMENT PUBLIC 'DATASG'		; Data Segment
	ASSUME DS:DSEG
	EXTRN	ARYTAB:WORD,DSCTMP:WORD,FRETOP:WORD,MEMSIZ:WORD
	EXTRN	STREND:WORD,TEMPPT:WORD,TEMPST:WORD,VALTYP:WORD,VARTAB:WORD
	EXTRN	TEMP8:WORD,ARYTA2:WORD
	EXTRN	TEMP9:WORD,PRMPRV:WORD
	EXTRN	FACLO:WORD
DSEG	ENDS			; End of data segment externals

				; Code Segment ( terminated by END at bottom of file )

	EXTRN	MOVRM:NEAR
	EXTRN	BLTUC:NEAR,CONINT:NEAR,CRFIN:NEAR,ERRLS:NEAR,ERROR:NEAR
	EXTRN	ERRSO:NEAR,ERRST:NEAR
	EXTRN	EVAL:NEAR,FCERR:NEAR,FOUT:NEAR,FRMEQL:NEAR,FRMEVL:NEAR
	EXTRN	FRMPRN:NEAR
	EXTRN	GETBYT:NEAR,OUTDO:NEAR,POPHRT:NEAR,PTRGET:NEAR,SIGNS:NEAR
	EXTRN	SNERR:NEAR
	EXTRN	TSTOP:NEAR,SNGFLT:NEAR,GIVDBL:NEAR,FIN:NEAR,CHKSTR:NEAR

	EXTRN	IADAHL:NEAR
	EXTRN	FINDBL:NEAR,GETBCD:NEAR,VMOVE:NEAR
	EXTRN	GETYPR:NEAR
	EXTRN	CHRGTR:NEAR,DCOMPR:NEAR,SYNCHR:NEAR

	PUBLIC	STRPRT,STROUI,LEN,FRESTR,STRCMP,VAL,STRLTI
	PUBLIC	FRETMS,FRETMP,RIGHT$,LEFT$,GARBA2,STR$
	PUBLIC	FRE,STRLIT,STRCPY,CAT,STRLT3,MID$
	PUBLIC	STRINI,STRIN1,STRAD1,PUTDEI,INCSTR

	PUBLIC	LHSMID

;
; THE FOLLOWING ROUTINE COMPARES TWO STRINGS
; ONE WITH DESC IN [D,E] OTHER WITH DESC. IN [FACLO, FACLO+1]
; A=0 IF STRINGS EQUAL
; A=377 IF B,C,D,E .GT. FACLO
; A=1 IF B,C,D,E .LT. FACLO
;
STRCMP:	CALL	FRESTR		;FREE UP THE FAC STRING, AND GET THE
				;POINTER TO THE FAC DESCRIPTOR IN [H,L]
	MOV	AL,BYTE PTR [BX]	;SAVE THE LENGTH OF THE FAC STRING IN [A]
	INC	BX
	MOV	CL,BYTE PTR [BX]	;SAVE THE POINTER AT THE FAC STRING
				;DATA IN [B,C]
	INC	BX
	MOV	CH,BYTE PTR [BX]
	POP	DX		;GET THE STACK STRING POINTER
	PUSH	CX		;SAVE THE POINTER AT THE FAC STRING DATA
	PUSH	AX		;SAVE THE FAC STRING LENGTH
	CALL	FRETMP		;FREE UP THE STACK STRING AND RETURN
				;THE POINTER TO THE STACK STRING DESCRIPTOR
				;IN [H,L]
	POP	AX		;GET BACK LENGTH OF STRING
	MOV	DH,AL		;[D]=LENGTH OF FAC STRING
	MOV	DL,BYTE PTR [BX]	;[E]=LENGTH OF STACK STRING
	INC	BX
	MOV	CL,BYTE PTR [BX]	;[B,C]=POINTER AT STACK STRING
	INC	BX
	MOV	CH,BYTE PTR [BX]
	POP	BX		;GET BACK 2ND CHARACTER POINTER
CSLOOP:	MOV	AL,DL		;BOTH STRINGS ENDED
	OR	AL,DH		;TEST BY OR'ING THE LENGTHS TOGETHER
	JNZ	SHORT $+3
	RET			;IF SO, RETURN WITH A ZERO
	MOV	AL,DH		;GET FACLO STRING LENGTH
	SUB	AL,LOW 1	;SET CARRY AND MAKE [A]=255 IF [D]=0
	JNB	SHORT $+3
	RET			;RETURN IF THAT STRING ENDED
	XOR	AL,AL		;MUST NOT HAVE BEEN ZERO, TEST CASE
	CMP	AL,DL		;OF B,C,D,E STRING HAVING ENDED FIRST
	INC	AL		;RETURN WITH A=1
	JNAE	SHORT $+3
	RET			;TEST THE CONDITION
;HERE WHEN NEITHER STRING ENDED
	DEC	DH		;DECREMENT BOTH CHARACTER COUNTS
	DEC	DL
	MOV	SI,CX
	MOV	AL,[SI]		;GET CHARACTER FROM B,C,D,E STRING
	INC	CX
	CMP	AL,BYTE PTR [BX]	;COMPARE WITH FACLO STRING
	LAHF
	INC	BX		;BUMP POINTERS (INX DOESNT CLOBBER CC'S)
	SAHF
	JZ	SHORT CSLOOP	;IF BOTH THE SAME, MUST BE MORE TO STRINGS
	CMC			;HERE WHEN STRINGS DIFFER
	JMP	SIGNS		;SET [A] ACCORDING TO CARRY
	SUBTTL  STRING FUNCTIONS
	EXTRN	FOUTO:NEAR,FOUTH:NEAR
	PUBLIC	STRO$,STRH$
; THE STRO$ FUNCTION TAKES A NUMBER AND GIVES
; A STRING WITH THE CHARACTERS THE NUMBER WOULD GIVE IF
; OUTPUT IN OCTAL
;
STRO$:	CALL	FOUTO		;PUT OCTAL NUMBER IN FBUFFR
	JMP	SHORT STR$1	;JUMP INTO STR$ CODE

; STRH$ SAME AS STRO$ EXCEPT USES HEX INSTEAD OF OCTAL
STRH$:	CALL	FOUTH		;PUT HEX NUMBER IN FBUFFR
	JMP	SHORT STR$1	;JUMP INTO STR$ CODE
;
; THE STR$ FUNCTION TAKES A NUMBER AND GIVES
; A STRING WITH THE CHARACTERS THE OUTPUT OF THE NUMBER
; WOULD HAVE GIVEN
;
STR$:
				;IS A NUMERIC
	CALL	FOUT		;DO ITS OUTPUT
STR$1:	CALL	STRLIT		;SCAN IT AND TURN IT INTO A STRING
	CALL	FREFAC		;FREE UP THE TEMP
	MOV	CX,OFFSET FINBCK
	PUSH	CX		;SET UP ANSWER IN NEW TEMP
;
; STRCPY CREATES A COPY OF THE STRING
; WHOSE DESCRIPTOR IS POINTED TO BY [H,L].
; ON RETURN [D,E] POINTS TO DSCTMP
; WHICH HAS THE STRING INFO (LENGTH,WHERE COPIED TO)
;
STRCPY:	MOV	AL,BYTE PTR [BX]	;GET LENGTH
	INC	BX		;MOVE UP TO THE POINTER
	PUSH	BX		;GET POINTER TO POINTER OF ARG
	CALL	GETSPA		;GET THE SPACE
	POP	BX		;FIND OUT WHERE STRING TO COPY
	MOV	CL,BYTE PTR [BX]
	INC	BX
	MOV	CH,BYTE PTR [BX]
	CALL	STRAD2		;SETUP DSCTMP
	PUSH	BX		;SAVE POINTER TO DSCTMP
	MOV	BL,AL		;GET CHARACTER COUNT INTO [L]
	CALL	MOVSTR		;MOVE THE CHARS IN
	POP	DX		;RESTORE POINTER TO DSCTMP
	RET			;RETURN

STRIN1:	MOV	AL,LOW 1	;MAKE ONE CHAR STRING (CHR$, INKEY$)
STRINI:	CALL	GETSPA		;GET SOME STRING SPACE ([A] CHARS)
STRAD2:	MOV	BX,OFFSET DSCTMP	;GET DESC. TEMP
STRAD1:	PUSH	BX		;SAVE DESC. POINTER
	MOV	BYTE PTR [BX],AL	;SAVE CHARACTER COUNT
PUTDEI:	INC	BX		;STORE [D,E]=POINTER TO FREE SPACE
	MOV	[BX],DX
	POP	BX		;AND RESTORE [H,L] AS THE DESCRIPTOR POINTER
	RET	
;
; STRLT2 TAKES THE STRING LITERAL WHOSE FIRST CHARACTER
; IS POINTED BY [H,L]+1 AND BUILDS A DESCRIPTOR FOR IT.
; THE DESCRIPTOR IS INITIALLY BUILT IN DSCTMP, BUT PUTNEW
; TRANSFERS IT INTO A TEMPORARY AND LEAVES A POINTER
; AT THE TEMPORARY IN FACLO. THE CHARACTERS OTHER THAN
; ZERO THAT TERMINATE THE STRING SHOULD BE SET UP IN [B]
; AND [D]. IT THE TERMINATOR IS A QUOTE, THE QUOTE IS SKIPPED
; OVER. LEADING QUOTES SHOULD BE SKIPPED BEFORE CALL. ON RETURN
; THE CHARACTER AFTER THE STRING LITERAL IS POINTED TO
; BY [H,L] AND IS IN [A], BUT THE CONDITION CODES ARE
; NOT SET UP.
;
	PUBLIC	STRLT2
STRLIT:	DEC	BX
STRLTI:	MOV	CH,LOW 34	;ASSUME STR ENDS ON QUOTE
STRLT3:	MOV	DH,CH
STRLT2:	PUSH	BX		;SAVE POINTER TO START OF LITERAL
	MOV	CL,LOW 255	;INITIALIZE CHARACTER COUNT
STRGET:	INC	BX
	MOV	AL,BYTE PTR [BX]	;GET CHAR
	INC	CL		;BUMP CHARACTER COUNT
	OR	AL,AL		;IF 0, (END OF LINE) DONE
	JZ	SHORT STRFIN	;TEST
	CMP	AL,DH
	JZ	SHORT STRFIN
	CMP	AL,CH		;CLOSING QUOTE
	JNZ	SHORT STRGET	;NO, GO BACK FOR MORE
STRFIN:	CMP	AL,LOW 34	;IF QUOTE TERMINATES THE STRING
	JNZ	SHORT ??L000
	CALL	CHRGTR		;SKIP OVER THE QUOTE
??L000:
	PUSH	BX		;SAVE POINTER AT END OF STRING
	MOV	AL,CH		;WERE WE SCANNING AN UNQUOTED STRING?
	CMP	AL,LOW 44
	JNZ	SHORT NTTRLS	;IF NOT, DON'T SUPPRESS TRAILING SPACES
	INC	CL		;FIX [C] WHICH IS THE CHARACTER COUNT
LPTRLS:	DEC	CL		;DECREMENT UNTIL WE FIND A NON-SPACE CHARACTER
	JZ	SHORT NTTRLS	;DON'T GO PAST START (ALL SPACES)
	DEC	BX		;LOOK AT PREVIOUS CHARACTER
	MOV	AL,BYTE PTR [BX]
	CMP	AL,LOW " "
	JZ	SHORT LPTRLS	;IF SO CONTINUE LOOKING
NTTRLS:	POP	BX
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI
	INC	BX
	XCHG	BX,DX		;GET POINTER TO TEMP
	MOV	AL,CL		;GET CHARACTER COUNT IN A
	CALL	STRAD2		;SAVE STR INFO
;
; SOME STRING FUNCTION IS RETURNING A RESULT IN DSCTMP
; WE WANT TO SETUP A TEMP DESCRIPTOR WITH DCSTMP IN IT
; PUT A POINTER TO THE DESCRIPTOR IN FACLO AND FLAG THE 
; RESULT AS TYPE STRING
;
	PUBLIC	PUTNEW
PUTNEW:	MOV	DX,OFFSET DSCTMP	;[D,E] POINT AT RESULT DESCRIPTOR
	PUBLIC	PUTTMP
	DB	260O	; SKIP	;SKIP THE NEXT BYTE ("MVI AL,")
PUTTMP:	PUSH	DX		;SAVE A POINTER TO THE START OF THE STRING
	MOV	BX,TEMPPT	;[H,L]=POINTER TO FIRST FREE TEMP
	MOV	FACLO,BX	;POINTER AT WHERE RESULT DESCRIPTOR WILL BE
	MOV	AL,LOW 3
	MOV	BYTE PTR VALTYP,AL	;FLAG THIS AS A STRING
	CALL	VMOVE		;AND MOVE THE VALUE INTO A TEMPORARY
	MOV	DX,OFFSET DSCTMP+3	;IF THE CALL IS TO PUTTMP, [D,E]
				;WILL NOT EQUAL DSCTMP +3
	CMP	BX,DX		;DSCTMP IS JUST BEYOND THE TEMPS
				;AND IF TEMPPT POINTS AT IT THERE
				;ARE NO FREE TEMPS
	MOV	TEMPPT,BX	;SAVE NEW TEMPORARY POINTER
	POP	BX		;GET THE TEXT POINTER
	MOV	AL,BYTE PTR [BX]	;GET CURRENT CHARACTER INTO [A]
	JZ	SHORT $+3
	RET
	MOV	DX,OFFSET ERRST	;"STRING TEMPORARY" ERROR
	JMP	ERROR		;GO TELL HIM
;
; PRINT THE STRING POINTED TO BY [H,L] WHICH ENDS WITH A ZERO
; IF THE STRING IS BELOW DSCTMP IT WILL BE COPIED INTO STRING SPACE
;
STROUI:	INC	BX		;POINT AT NEXT CHARACTER
	PUBLIC	DSOUT
DSOUT:				;PRINT FROM THE DATA SEGMENT
	CALL	STRLIT		;GET A STRING LITERAL
;
; PRINT THE STRING WHOSE DESCRIPTOR IS POINTED TO BY FACLO.
;
STRPRT:	CALL	FREFAC		;RETURN TEMP POINTER BY FACLO
	CALL	GETBCD		;[D]=LENGTH [B,C]=POINTER AT DATA
	INC	DH		;INCREMENT AND DECREMENT EARLY
				;TO CHECK FOR NULL STRING
STRPR2:	DEC	DH		;DECREMENT THE LENGTH
	JNZ	SHORT $+3
	RET			;ALL DONE
	MOV	SI,CX
	MOV	AL,[SI]		;GET CHARACTER TO PRINT
	CALL	OUTDO
	CMP	AL,LOW 13
	JNZ	SHORT ??L001
	CALL	CRFIN
??L001:
	INC	CX		;POINT TO THE NEXT CHARACTER
	JMP	SHORT STRPR2	;AND PRINT IT...
	PAGE	
	SUBTTL  STRING GARBAGE COLLECTION - GETSPA, GARBAG
;
; GETSPA - GET SPACE FOR CHARACTER STRING
; MAY FORCE GARBAGE COLLECTION.
;
; # OF CHARS (BYTES) IN [A]
; RETURNS WITH POINTER IN [D,E] OTHERWISE IF CANT GET SPACE
; BLOWS OFF TO "OUT OF STRING SPACE" TYPE ERROR.
;
	PUBLIC	GETSPA
GETSPA:	OR	AL,AL		;MUST BE NON ZERO. SIGNAL NO GARBAG YET
	JMP	SHORT TRYGI3
TRYGI2:	POP	AX
	SAHF			;IN CASE COLLECTED WHAT WAS LENGTH?
TRYGI3:
	LAHF
	PUSH	AX		;SAVE IT BACK
	MOV	BX,STREND
	XCHG	BX,DX		;IN [D,E]
	MOV	BX,FRETOP	;GET TOP OF FREE SPACE IN [H,L]
	NOT	AL		;-# OF CHARS
	MOV	CL,AL		;IN [B,C]
	MOV	CH,LOW 255
	ADD	BX,CX		;SUBTRACT FROM TOP OF FREE
	INC	BX
	CMP	BX,DX		;COMPARE THE TWO
	JB	SHORT GARBAG	;NOT ENOUGH ROOM FOR STRING, OFFAL TIME
	MOV	FRETOP,BX	;SAVE NEW BOTTOM OF MEMORY
	INC	BX		;MOVE BACK TO POINT TO STRING
	XCHG	BX,DX		;RETURN WITH POINTER IN [D,E]
	POP	AX
	SAHF
	RET	
	PUBLIC	PPSWRT
PPSWRT:	POP	AX		; POP PSW
	XCHG	AL,AH
	SAHF			;GET CHARACTER COUNT
	RET			;RETURN FROM GETSPA

GARBAG:
	POP	AX
	SAHF			;HAVE WE COLLECTED BEFORE?
	MOV	DX,OFFSET ERRSO	;GET READY FOR OUT OF STRING SPACE ERROR
	JNZ	SHORT ??L002
	JMP	ERROR		;GO TELL USER HE LOST
??L002:
	CMP	AL,AL		;SET ZERO FLAG TO SAY WEVE GARBAGED
	LAHF
	PUSH	AX		;SAVE FLAG BACK ON STACK
	MOV	CX,OFFSET TRYGI2	;PLACE FOR GARBAG TO RETURN TO.
	PUSH	CX		;SAVE ON STACK
GARBA2:
	MOV	BX,MEMSIZ	;START FROM TOP DOWN
FNDVAR:	MOV	FRETOP,BX	;LIKE SO
	MOV	BX,0		;GET DOUBLE ZERO
	PUSH	BX		;SAY DIDNT SEE VARS THIS PASS
	MOV	BX,STREND	;FORCE DVARS TO IGNORE STRINGS
				;IN THE PROGRAM TEXT (LITERALS, DATA)
	PUSH	BX		;FORCE FIND HIGH ADDRESS
	MOV	BX,OFFSET TEMPST	;GET START OF STRING TEMPS
TVAR:	MOV	DX,TEMPPT	;SEE IF DONE
	CMP	BX,DX		;TEST
	MOV	CX,OFFSET TVAR	;FORCE JUMP TO TVAR
	JZ	SHORT ??L003
	JMP	DVAR2		;DO TEMP VAR GARBAGE COLLECT
??L003:

	MOV	BX,OFFSET PRMPRV	;SETUP ITERATION FOR PARAMETER BLOCKS
	MOV	TEMP9,BX
	MOV	BX,ARYTAB	;GET STOPPING POINT IN [H,L]
	MOV	ARYTA2,BX	;STORE IN STOP LOCATION
	MOV	BX,VARTAB	;GET STARTING POINT IN [H,L]
SVAR:	MOV	DX,ARYTA2	;GET STOPPING LOCATION
	CMP	BX,DX		;SEE IF AT END OF SIMPS
	JZ	SHORT ARYVAR
	MOV	AL,BYTE PTR [BX]	;GET VALTYP
	INC	BX		;BUMP POINTER TWICE
	INC	BX		;
	INC	BX		;POINT AT THE VALUE
	PUSH	AX		;SAVE VALTYP
	CALL	IADAHL		;AND SKIP OVER EXTRA CHARACTERS AND COUNT
	POP	AX
	CMP	AL,LOW 3	;SEE IF ITS A STRING
	JNZ	SHORT SKPVAR	;IF NOT, JUST SKIP AROUND IT
	CALL	DVARS		;COLLECT IT
	XOR	AL,AL		;AND DON'T SKIP ANYTHING MORE
SKPVAR:	MOV	DL,AL
	MOV	DH,LOW 0	;[D,E]=AMOUNT TO SKIP
	ADD	BX,DX
	JMP	SHORT SVAR	;GET NEXT ONE
ARYVAR:	MOV	BX,TEMP9	;GET LINK IN PARAMETER BLOCK CHAIN
	MOV	DX,[BX]		;GO BACK ONE LEVEL
	OR	DX,DX		;WAS THAT THE END?
	MOV	BX,ARYTAB	;SETUP TO START ARRAYS
	JZ	SHORT ARYVA4	;OTHERWISE GARBAGE COLLECT ARRAYS
	XCHG	BX,DX
	MOV	TEMP9,BX	;SETUP NEXT LINK IN CHAIN FOR ITERATION
	INC	BX		;SKIP CHAIN POINTER
	INC	BX
	MOV	DX,[BX]		;PICK UP THE LENGTH
	INC	BX
	INC	BX
	XCHG	BX,DX		;SET [D,E]= ACTUAL END ADDRESS BY
	ADD	BX,DX		;ADDING BASE TO LENGTH
	MOV	ARYTA2,BX	;SET UP STOP LOCATION
	XCHG	BX,DX
	JMP	SHORT SVAR

ARYVA2:	POP	CX		;GET RID OF STACK GARBAGE
ARYVA4:	MOV	DX,STREND	;GET END OF ARRAYS
	CMP	BX,DX		;SEE IF DONE WITH ARRAYS
	JNZ	SHORT ??L004
	JMP	GRBPAS		;YES, SEE IF DONE COLLECTING
??L004:
	MOV	AL,BYTE PTR [BX]	;GET THE VALUE TYPE INTO [A]
	INC	BX
	PUSH	AX		;SAVE THE VALTYP
	INC	BX		;SKIP THE NAME CHARACTERS
	INC	BX
	CALL	IADAHL		;SKIP THE EXTRA CHARACTERS
	MOV	CL,BYTE PTR [BX]	;PICK UP THE LENGTH
	INC	BX
	MOV	CH,BYTE PTR [BX]
	INC	BX
	POP	AX		;RESTORE THE VALTYP
	PUSH	BX		;SAVE POINTER TO DIMS
	ADD	BX,CX		;ADD TO CURRENT POINTER POSITION
	CMP	AL,LOW 3	;SEE IF ITS A STRING
	JNZ	SHORT ARYVA2	;IF NOT JUST SKIP IT
	MOV	TEMP8,BX	;SAVE END OF ARRAY
	POP	BX		;GET BACK CURRENT POSITION
	MOV	CL,BYTE PTR [BX]	;PICK UP NUMBER OF DIMS
	MOV	CH,LOW 0	;MAKE DOUBLE WITH HIGH ZERO
	ADD	BX,CX		;GO PAST DIMS
	ADD	BX,CX		;BY ADDING ON TWICE #DIMS (2 BYTE GUYS)
	INC	BX		;ONE MORE TO ACCOUNT FOR #DIMS.
ARYSTR:	XCHG	BX,DX		;SAVE CURRENT POSIT IN [D,E]
	MOV	BX,TEMP8	;GET END OF ARRAY
	XCHG	BX,DX		;FIX [H,L] BACK TO CURRENT
	CMP	BX,DX		;SEE IF AT END OF ARRAY
	JZ	SHORT ARYVA4	;END OF ARRAY, TRY NEXT ARRAY
	MOV	CX,OFFSET ARYSTR	;ADDR OF WHERE TO RETURN TO
DVAR2:	PUSH	CX		;GOES ON STACK
DVAR:
DVARS:	XOR	AL,AL
	OR	AL,BYTE PTR [BX]	;SEE IF ITS THE NULL STRING
	LAHF
	INC	BX
	SAHF
	MOV	DL,BYTE PTR [BX]
	LAHF
	INC	BX
	SAHF
	MOV	DH,BYTE PTR [BX]
	LAHF
	INC	BX		;[D,E]=POINTER AT THE VALUE
	SAHF
	JNZ	SHORT $+3
	RET			;NULL STRING, RETURN
	MOV	CX,BX		;MOVE [H,L] TO [B,C]
	MOV	BX,FRETOP	;GET POINTER TO TOP OF STRING FREE SPACE
	CMP	BX,DX		;IS THIS STRINGS POINTER .LT. FRETOP
	MOV	BX,CX		;MOVE [B,C] BACK TO [H,L]
	JNB	SHORT $+3
	RET			;IF NOT, NO NEED TO MESS WITH IT FURTHUR
	POP	BX		;GET RETURN ADDRESS OFF STACK
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;GET MAX SEEN SO FAR & SAVE RETURN ADDRESS
	CMP	BX,DX		;LETS SEE
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;SAVE MAX SEEN & GET RETURN ADDRESS OFF STACK
	PUSH	BX		;SAVE RETURN ADDRESS BACK
	MOV	BX,CX		;MOVE [B,C] BACK TO [H,L]
	JNAE	SHORT $+3
	RET			;IF NOT, LETS LOOK AT NEXT VAR
	POP	CX		;GET RETURN ADDR OFF STACK
	POP	AX		;POP OFF MAX SEEN
	POP	AX		;AND VARIABLE POINTER
	PUSH	BX		;SAVE NEW VARIABLE POINTER
	PUSH	DX		;AND NEW MAX POINTER
	PUSH	CX		;SAVE RETURN ADDRESS BACK
	RET			;AND RETURN
;
; HERE WHEN MADE ONE COMPLETE PASS THRU STRING VARS
;
GRBPAS:	POP	DX		;POP OFF MAX POINTER
	POP	BX		;AND GET VARIABLE POINTER
	OR	BX,BX		;SEE IF ZERO POINTER
	JNZ	SHORT $+3
	RET			;IF END OF COLLECTION,
				;THEN MAYBE RETURN TO GETSPA
	DEC	BX		;CURRENTLY JUST PAST THE DESCRIPTOR
	MOV	CH,BYTE PTR [BX]	;[B]=HIGH BYTE OF DATA POINTER
	DEC	BX
	MOV	CL,BYTE PTR [BX]	;[B,C]=POINTER AT STRING DATA
	PUSH	BX		;SAVE THIS LOCATION SO THE POINTER
				;CAN BE UPDATED AFTER THE STRING IS
				;MOVED
	DEC	BX
	MOV	BL,BYTE PTR [BX]	;[L]=STRING LENGTH
	MOV	BH,LOW 0	;[H,L] GET CHARACTER COUNT
	ADD	BX,CX		;[H,L]=POINTER BEYOND STRING
	MOV	DH,CH
	MOV	DL,CL		;[D,E]=ORIGINAL POINTER
	DEC	BX		;DON'T MOVE ONE BEYOND STRING
	MOV	CX,BX		;GET TOP OF STRING IN [B,C]
	MOV	BX,FRETOP	;GET TOP OF FREE SPACE
	CALL	BLTUC		;MOVE STRING
	POP	BX		;GET BACK POINTER TO DESC.
	MOV	BYTE PTR [BX],CL	;SAVE FIXED ADDR
	INC	BX		;MOVE POINTER
	MOV	BYTE PTR [BX],CH	;HIGH PART
	MOV	BX,CX		;[H,L]=NEW POINTER
	DEC	BX		;FIX UP FRETOP
	JMP	FNDVAR		;AND TRY TO FIND HIGH AGAIN

	PAGE	
	SUBTTL  STRING CONCATENATION
;
; THE FOLLOWING ROUTINE CONCATENATES TWO STRINGS
; THE FACLO CONTAINS THE FIRST ONE AT THIS POINT,
; [H,L] POINTS BEYOND THE + SIGN AFTER IT
;
CAT:	PUSH	CX		;PUT OLD PRECEDENCE BACK ON
	PUSH	BX		;SAVE TEXT POINTER
	MOV	BX,FACLO	;GET POINTER TO STRING DESC.
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;SAVE ON STACK & GET TEXT POINTER BACK
	CALL	EVAL		;EVALUATE REST OF FORMULA
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;SAVE TEXT POINTER, GET BACK DESC.
	CALL	CHKSTR
	MOV	AL,BYTE PTR [BX]
	PUSH	BX		;SAVE DESC. POINTER.
	MOV	BX,FACLO	;GET POINTER TO 2ND DESC.
	PUSH	BX		;SAVE IT
	ADD	AL,BYTE PTR [BX]	;ADD TWO LENGTHS TOGETHER
	MOV	DX,OFFSET ERRLS	;SEE IF RESULT .LT. 256
	JAE	SHORT ??L005
	JMP	ERROR		;ERROR "LONG STRING"
??L005:
	CALL	STRINI		;GET INITIAL STRING
	POP	DX		;GET 2ND DESC.
	CALL	FRETMP
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;SAVE POINTER TO IT
	CALL	FRETM2		;FREE UP 1ST TEMP
	PUSH	BX		;SAVE DESC. POINTER (FIRST)
	INCSTR=2
	INCSTR=1
	MOV	BX,DSCTMP+INCSTR	;GET POINTER TO FIRST
	XCHG	BX,DX		;IN [D,E]
	CALL	MOVINS		;MOVE IN THE FIRST STRING
	CALL	MOVINS		;AND THE SECOND
	MOV	BX,OFFSET TSTOP	;CAT REENTERS FORMULA EVALUATION AT TSTOP
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI
	PUSH	BX		;TEXT POINTER OFF FIRST
	JMP	PUTNEW		;THEN RETURN ADDRESS OF TSTOP


MOVINS:	POP	BX		;GET RETURN ADDR
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;PUT BACK, BUT GET DESC.
	MOV	AL,BYTE PTR [BX]	;[A]=STRING LENGTH
	INC	BX
	MOV	CL,BYTE PTR [BX]	;[B,C]=POINTER AT STRING DATA
	INC	BX
	MOV	CH,BYTE PTR [BX]
	MOV	BL,AL		;[L]=STRING LENGTH
MOVSTR:	INC	BL
MOVLP:	DEC	BL		;SET CC'S
	JNZ	SHORT $+3
	RET			;0, NO BYTE TO MOVE
	MOV	SI,CX
	MOV	AL,[SI]		;GET CHAR
	MOV	DI,DX
	STOSB			;SAVE IT
	INC	CX		;MOVE POINTERS
	INC	DX
	JMP	SHORT MOVLP	;KEEP DOING IT
	PAGE	
	SUBTTL  FREE UP STRING TEMPORARY - FRESTR, FREFAC, FRETMP, FRETMS
;
; FRETMP IS PASSED A POINTER TO A STRING DESCRIPTOR IN [D,E]
; THIS VALUE IS RETURNED IN [H,L]. ALL THE OTHER REGISTERS ARE MODIFIED.
; A CHECK TO IS MADE TO SEE IF THE STRING DESCRIPTOR [D,E] POINTS
; TO IS THE LAST TEMPORARY DESCRIPTOR ALLOCATED BY PUTNEW.
; IF SO, THE TEMPORARY IS FREED UP BY THE UPDATING OF TEMPPT.
; IF A TEMPORARY IS FREED UP, A FURTHER CHECK IS MADE TO SEE IF THE
; STRING DATA THAT THAT STRING TEMPORARY POINTED TO IS THE
; THE LOWEST PART OF STRING SPACE IN USE.
; IF SO, FRETMP IS UPDATED TO REFLECT THE FACT THAT THAT SPACE IS NO
; LONGER IN USE.
;
	PUBLIC	FREFAC
FRESTR:	CALL	CHKSTR		;MAKE SURE ITS A STRING
FREFAC:	MOV	BX,FACLO
	PUBLIC	FRETM2
FRETM2:	XCHG	BX,DX		;FREE UP THE TEMP IN THE FACLO
FRETMP:	CALL	FRETMS		;FREE UP THE TEMPORARY
	XCHG	BX,DX		;PUT THE STRING POINTER INTO [H,L]
	JZ	SHORT $+3
	RET
	PUSH	DX		;SAVE [D,E] TO RETURN IN [H,L]
	MOV	DH,CH		;[D,E]=POINTER AT STRING
	MOV	DL,CL
	DEC	DX		;SUBTRACT ONE
	MOV	CL,BYTE PTR [BX]	;[C]=LENGTH OF THE STRING FREED UP
	MOV	BX,FRETOP	;SEE IF ITS THE FIRST 
				;ONE IN STRING SPACE
	CMP	BX,DX
	JNZ	SHORT NOTLST	;NO SO DON'T ADD
	XOR	AL,AL		;MUST EXPLICITLY ZERO A
	MOV	CH,AL		;MAKE [B]=0
	ADD	BX,CX		;ADD
	MOV	FRETOP,BX	;AND UPDATE FRETOP
NOTLST:	POP	BX		;GET POINTER AT CURRENT DESCRIPTOR
	RET	
FRETMS:
	MOV	BX,TEMPPT	;GET TEMP POINTER
	DEC	BX		;LOOK AT WHAT IS IN THE LAST TEMP
	MOV	CH,BYTE PTR [BX]	;[B,C]=POINTER AT STRING
	DEC	BX		;DECREMENT TEMPPT BY STRSIZ
	MOV	CL,BYTE PTR [BX]
	DEC	BX
	CMP	BX,DX		;SEE IF [D,E] POINT AT THE LAST 
	JZ	SHORT $+3
	RET			;RETURN NOW IF NOW FREEING DONE
	MOV	TEMPPT,BX	;UPDATE THE TEMP POINTER SINCE
				;ITS BEEN DECREMENTED BY 4
	RET	
	PAGE	
	SUBTTL STRING FUNCTIONS - LEN, ASC, CHR$
;
; THE FUNCTION LEN($) RETURNS THE LENGTH OF THE
; STRING PASSED AS AN ARGUMENT
;
LEN:	MOV	CX,OFFSET SNGFLT	;CALL SNGFLT WHEN DONE
	PUSH	CX		;LIKE SO
LEN1:	CALL	FRESTR		;FREE UP TEMP POINTED TO BY FACLO
	XOR	AL,AL		;FORCE NUMERIC FLAG
	MOV	DH,AL		;SET HIGH OF [D,E] TO ZERO FOR VAL
	MOV	AL,BYTE PTR [BX]
	OR	AL,AL		;SET CONDITION CODES ON LENGTH
	RET			;RETURN

; THE FOLLOWING IS THE ASC($) FUNCTION. IT RETURNS AN INTEGER
; WHICH IS THE DECIMAL ASCII EQUIVALENT
;
	PUBLIC	ASC,ASC2
ASC:
	MOV	CX,OFFSET SNGFLT	;WHERE TO GO WHEN DONE
	PUSH	CX		;SAVE RETURN ADDR ON STACK
ASC2:	CALL	LEN1		;SET UP ORIGINAL STR
	JNZ	SHORT ??L006
	JMP	FCERR		;NULL STR, BAD ARG.
??L006:
	INC	BX		;BUMP POINTER
	MOV	DX,[BX]		;[D,E]=POINTER AT STRING DATA
	MOV	SI,DX
	MOV	AL,[SI]		;[A]=FIRST CHARACTER
	RET	
;
; CHR$(#) CREATES A STRING WHICH CONTAINS AS ITS ONLY
; CHARACTER THE ASCII EQUIVALENT OF THE INTEGER ARG (#)
; WHICH MUST BE .LE. 255.
;
	PUBLIC	CHR$
CHR$:	CALL	STRIN1		;GET STRING IN DSCTMP
	CALL	CONINT		;GET INTEGER IN RANGE
	INCSTR=2
	INCSTR=1
	PUBLIC	SETSTR,FINBCK
SETSTR:	MOV	BX,DSCTMP+INCSTR	;GET ADDR OF STR
	MOV	BYTE PTR [BX],DL	;SAVE ASCII BYTE
FINBCK:	POP	CX		;RETURN TO HIGHER LEVEL &
				;SKIP THE CHKNUM CALL.
	JMP	PUTNEW		;GO CALL PUTNEW

	PUBLIC	STRNG$
STRNG$:	CALL	CHRGTR		;GET NEXT CHAR FOLLOWING "STRING$"
	CALL	SYNCHR
	DB	OFFSET "("	;MAKE SURE LEFT PAREN
	CALL	GETBYT		;EVALUATE FIRST ARG (LENGTH)
	PUSH	DX		;SAVE IT
	CALL	SYNCHR
	DB	OFFSET 54O	;COMMA
	CALL	FRMEVL		;GET FORMULA ARG 2
	CALL	SYNCHR
	DB	OFFSET ")"	;EXPECT RIGHT PAREN
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;SAVE TEXT POINTER ON STACK, GET REP FACTOR
	PUSH	BX		;SAVE BACK REP FACTOR
	CALL	GETYPR		;GET TYPE OF ARG
	JZ	SHORT STRSTR	;WAS A STRING
	CALL	CONINT		;GET ASCII VALUE OF CHAR
	JMP	SHORT CALSPA	;NOW CALL SPACE CODE
STRSTR:	CALL	ASC2		;GET VALUE OF CHAR IN [A]
CALSPA:	POP	DX		;GET REP FACTOR IN [E]
	CALL	SPACE2		;INTO SPACE CODE, PUT DUMMY ENTRY
				;ON STACK POPPED OFF BY FINBCK

	PUBLIC	SPACE$
SPACE$:	CALL	CONINT		;GET NUMBER OF CHARS IN [E]
	MOV	AL,LOW 32	;GET SPACE CHAR
SPACE2:	PUSH	AX		;SAVE CHAR
	MOV	AL,DL		;GET NUMBER OF CHARS IN [A]
	CALL	STRINI		;GET A STRING THAT LONG
	MOV	CH,AL		;COUNT OF CHARS BACK IN [B]
	POP	AX		;GET BACK CHAR TO PUT IN STRING
	INC	CH		;TEST FOR NULL STRING
	DEC	CH
	JZ	SHORT FINBCK	;YES, ALL DONE
	MOV	BX,DSCTMP+INCSTR	;GET DESC. POINTER
SPLP$:	MOV	BYTE PTR [BX],AL	;SAVE CHAR
	INC	BX		;BUMP PTR
				;DECR COUNT
	DEC	CH
	JNZ	SHORT SPLP$	;KEEP STORING CHAR
	JMP	SHORT FINBCK	;PUT TEMP DESC WHEN DONE
	PAGE	
	SUBTTL STRING FUNCTIONS - LEFT$, RIGHT$, MID$
;
; THE FOLLOWING IS THE LEFT$($,#) FUNCTION.
; IT TAKES THE LEFTMOST # CHARS OF THE STR.
; IF # IS .GT. THAN THE LEN OF THE STR, IT RETURNS THE WHOLE STR.
;
LEFT$:	CALL	PREAM		;TEST THE PARAMETERS
	XOR	AL,AL		;LEFT NEVER CHANGES STRING POINTER
LEFT3:	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;SAVE TEXT POINTER
	MOV	CL,AL		;OFFSET NOW IN [C]
	DB	260O	; SKIP	;SKIP THE NEXT BYTE WITH "MVI A,"
;
; THIS IS PRINT USINGS ENTRY POINT INTO LEFT$
;
	PUBLIC	LEFTUS
LEFTUS:	PUSH	BX		;THIS IS A DUMMY PUSH TO OFFSET
				;THE EXTRA POP IN PUTNEW
LEFT2:	PUSH	BX		;SAVE DESC. FOR  FRETMP
	MOV	AL,BYTE PTR [BX]	;GET STRING LENGTH
	CMP	AL,CH		;ENTIRE STRING WANTED?
	JB	SHORT ALLSTR	;IF #CHARS ASKED FOR.GE.LENGTH,YES
	MOV	AL,CH		;GET TRUNCATED LENGTH OF STRING
	DB	272O	; SKIP	;SKIP OVER MVI USING "LXI D,"
ALLSTR:	MOV	CL,LOW 0	;MAKE OFFSET ZERO
	PUSH	CX		;SAVE OFFSET ON STACK
	CALL	GETSPA		;GET SPACE FOR NEW STRING
	POP	CX		;GET BACK OFFSET
	POP	BX		;GET BACK DESC POINTER.
	PUSH	BX		;BUT KEEP ON STACK
	INC	BX		;MOVE TO STRING POINTER FIELD
	MOV	CH,BYTE PTR [BX]	;GET POINTER LOW
	INC	BX		;
	MOV	BH,BYTE PTR [BX]	;POINTER HIGH
	MOV	BL,CH		;GET LOW IN  L
	MOV	CH,LOW 0	;GET READY TO ADD OFFSET TO POINTER
	ADD	BX,CX		;ADD  IT
	MOV	CX,BX		;GET OFFSET POINTER IN [B,C]
	CALL	STRAD2		;SAVE INFO IN DSCTMP
	MOV	BL,AL		;GET#  OF CHARS TO  MOVE IN L
	CALL	MOVSTR		;MOVE THEM IN
	POP	DX		;GET BACK DESC. POINTER
	CALL	FRETMP		;FREE IT UP.
	JMP	PUTNEW		;PUT TEMP IN TEMP LIST

RIGHT$:	CALL	PREAM		;CHECK ARG
	POP	DX		;GET DESC. POINTER
	PUSH	DX		;SAVE BACK FOR LEFT
	MOV	SI,DX
	MOV	AL,[SI]		;GET PRESENT LEN OF STR
	SUB	AL,CH		;SUBTRACT 2ND PARM
	JMP	SHORT LEFT3	;CONTINUE WITH LEFT CODE
;
; MID ($,#) RETURNS STR WITH CHARS FROM # POSITION
; ONWARD. IF # IS GT LEN($) THEN RETURN NULL STRING.
; MID ($,#,#) RETURNS STR WITH CHARS FROM # POSITION
; FOR #2 CHARS. IF #2 GOES PAST END OF STRING, RETURN
; AS MUCH AS POSSIBLE.
;
MID$:	XCHG	BX,DX		;PUT THE TEXT POINTER IN [H,L]
	MOV	AL,BYTE PTR [BX]	;GET THE FIRST CHARACTER
	CALL	PREAM2		;GET OFFSET OFF STACK AND MAKE
	INC	CH
	DEC	CH		;SEE IF EQUAL TO ZERO
	JNZ	SHORT ??L007
	JMP	FCERR		;IT MUST NOT BE 0
??L007:
	PUSH	CX		;PUT OFFSET ON TO THE STACK
	CALL	MIDRST		;DUPLICATE OF CODE CONDITIONED OUT
	POP	AX		; POP PSW
	XCHG	AL,AH
	SAHF			;GET OFFSET BACK IN A
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;SAVE TEXT POINTER, GET DESC.
	MOV	CX,OFFSET LEFT2	;WHERE TO RETURN TO.
	PUSH	CX		;GOES ON STACK
	DEC	AL		;SUB ONE FROM OFFSET
	CMP	AL,BYTE PTR [BX]	;POINTER PAST END OF STR?
	MOV	CH,LOW 0	;ASSUME NULL LENGTH STR
	JNAE	SHORT $+3
	RET			;YES, JUST USE NULL STR
	MOV	CL,AL		;SAVE OFFSET OF CHARACTER POINTER
	MOV	AL,BYTE PTR [BX]	;GET PRESENT LEN OF STR
	SUB	AL,CL		;SUBTRACT INDEX (2ND ARG)
	CMP	AL,DL		;IS IT TRUNCATION
	MOV	CH,AL		;GET CALCED LENGTH IN B
	JNB	SHORT $+3
	RET			;IF NOT USE PARTIAL STR
	MOV	CH,DL		;USE TRUNCATED LENGTH
	RET			;RETURN TO LEFT2
;
; THE VAL FUNCTION TAKES A STRING AND TURN IT INTO
; A NUMBER BY INTERPRETING THE ASCII DIGITS. ETC..
; EXCEPT FOR THE PROBLEM THAT A TERMINATOR MUST BE SUPPLIED
; BY REPLACING THE CHARACTER BEYOND THE STRING, VAL
; IS MERELY A CALL TO FLOATING INPUT (FIN).
;
VAL:	CALL	LEN1		;DO SETUP, SET RESULT=REAL
	JNZ	SHORT ??L008
	JMP	SNGFLT
??L008:				;MAKE SURE TYPE SET UP OK IN EXTENDED
	MOV	DL,AL		;GET LENGTH OF STR
	INC	BX		;TO HANDLE THE FACT THE IF
	MOV	BX,[BX]		;TWO STRINGS "1" AND "2" ARE STORED
				;NEXT TO EACH OTHER
	PUSH	BX		;AND FIN IS CALLED POINTING TO
	ADD	BX,DX		;THE FIRST TWELVE WILL BE RETURNED
	MOV	CH,BYTE PTR [BX]	;THE IDEA IS TO STORE 0 IN THE
	MOV	BYTE PTR [BX],DH	;STRING BEYOND THE ONE VAL
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;IS BEING CALLED ON
	PUSH	CX		;THE FIRST CHARACTER OF THE NEXT STRING
	DEC	BX		;***CALL CHRGET TO MAKE SURE
	CALL	CHRGTR		;VAL(" -3")=-3
	CALL	FINDBL		;IN EXTENDED, GET ALL THE PRECISION WE CAN
	POP	CX		;GET THE MODIFIED CHARACTER OF THE NEXT
				;STRING INTO [B]
	POP	BX		;GET THE POINTER TO THE MODIFIED CHARACTER
	MOV	BYTE PTR [BX],CH	;RESTORE THE CHARACTER
				;IF STRING IS HIGHEST IN STRING SPACE
				;WE ARE MODIFYING [MEMSIZ] AND
				;THIS IS WHY [MEMSIZ] CAN'T BE USED TO STORE
				;STRING DATA BECAUSE WHAT IF THE
				;USER TOOK VAL OFF THAT HIGH STRING
	RET	
;USED BY RIGHT$ AND LEFT$ FOR PARAMETER CHECKING AND SETUP
PREAM:	XCHG	BX,DX		;PUT THE TEXT POINTER IN [H,L]
	CALL	SYNCHR
	DB	OFFSET ")"	;PARAM LIST SHOULD END
;USED BY MID$ FOR PARAMETER CHECKING AND SETUP
PREAM2:	POP	CX		;GET RETURN ADDR OFF STACK
	POP	DX		;GET LENGTH OF ARG OFF STACK
	PUSH	CX		;SAVE RETURN ADDR BACK ON
	MOV	CH,DL		;SAVE INIT LENGTH
	RET	

	PAGE	
	SUBTTL STRING FUNCTIONS - INSTR

; THIS IS THE INSTR FUCNTION. IT TAKES ONE OF TWO
; FORMS: INSTR(I%,S1$,S2$) OR INSTR(S1$,S2$)
; IN THE FIRST FORM THE STRING S1$ IS SEARCHED FOR THE
; CHARACTER S2$ STARTING AT CHARACTER POSITION I%.
; THE SECOND FORM IS IDENTICAL, EXCEPT THAT THE SEARCH
; STARTS AT POSITION 1. INSTR RETURNS THE CHARACTER
; POSITION OF THE FIRST OCCURANCE OF S2$ IN S1$.
; IF S1$ IS NULL, 0 IS RETURNED. IF S2$ IS NULL, THEN
; I% IS RETURNED, UNLESS I% .GT. LEN(S1$) IN WHICH
; CASE 0 IS RETURNED.

	PUBLIC	INSTR
INSTR:	CALL	CHRGTR		;EAT FIRST CHAR
	CALL	FRMPRN		;EVALUATE FIRST ARG
	CALL	GETYPR		;SET ZERO IF ARG A STRING.
	MOV	AL,LOW 1	;IF SO, ASSUME, SEARCH STARTS AT FIRST CHAR
	PUSH	AX		;SAVE OFFSET IN CASE STRING
	JZ	SHORT WUZSTR	;WAS A STRING
	POP	AX		;GET RID OF SAVED OFFSET
	CALL	CONINT		;FORCE ARG1 (I%) TO BE INTEGER
	OR	AL,AL		;DONT ALLOW ZERO OFFSET
	JNZ	SHORT ??L009
	JMP	FCERR		;KILL HIM.
??L009:
	PUSH	AX		;SAVE FOR LATER
	CALL	SYNCHR
	DB	OFFSET 44	;EAT THE COMMA
	CALL	FRMEVL		;EAT FIRST STRING ARG
	CALL	CHKSTR		;BLOW UP IF NOT STRING
WUZSTR:	CALL	SYNCHR
	DB	OFFSET 44	;EAT COMMA AFTER ARG
	PUSH	BX		;SAVE THE TEXT POINTER
	MOV	BX,FACLO	;GET DESCRIPTOR POINTER
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;PUT ON STACK & GET BACK TEXT PNT.
	CALL	FRMEVL		;GET LAST ARG
	CALL	SYNCHR
	DB	OFFSET ")"	;EAT RIGHT PAREN
	PUSH	BX		;SAVE TEXT POINTER
	CALL	FRESTR		;FREE UP TEMP & CHECK STRING
	XCHG	BX,DX		;SAVE 2ND DESC. POINTER IN [D,E]
	POP	CX		;GET TEXT POINTER IN B
	POP	BX		;DESC. POINTER FOR S1$
	POP	AX		;OFFSET
	PUSH	CX		;PUT TEXT POINTER ON BOTTOM
	MOV	CX,OFFSET POPHRT	;PUT ADDRESS OF POP H, RET ON
	PUSH	CX		;PUSH IT
	MOV	CX,OFFSET SNGFLT	;NOW ADDRESS OF [A] RETURNER
	PUSH	CX		;ONTO STACK
	PUSH	AX		;SAVE OFFSET BACK
	PUSH	DX		;SAVE DESC. OF S2
	CALL	FRETM2		;FREE UP S1 DESC.
	POP	DX		;RESTORE DESC. S2
	POP	AX		;GET BACK OFFSET
	MOV	CH,AL		;SAVE UNMODIFIED OFFSET
	DEC	AL		;MAKE OFFSET OK
	MOV	CL,AL		;SAVE IN C
	CMP	AL,BYTE PTR [BX]	;IS IT BEYOND LENGTH OF S1?
	MOV	AL,LOW 0	;IF SO, RETURN ZERO. (ERROR)
	JNAE	SHORT $+3
	RET
	MOV	SI,DX
	MOV	AL,[SI]		;GET LENGTH OF S2$
	OR	AL,AL		;NULL??
	MOV	AL,CH		;GET OFFSET BACK
	JNZ	SHORT $+3
	RET			;ALL IF S2 NULL, RETURN OFFSET
	MOV	AL,BYTE PTR [BX]	;GET LENGTH OF S1$
	INC	BX		;BUMP POINTER
	MOV	CH,BYTE PTR [BX]	;GET 1ST BYTE OF ADDRESS
	INC	BX		;BUMP POINTER
	MOV	BH,BYTE PTR [BX]	;GET 2ND BYTE
	MOV	BL,CH		;GET 1ST BYTE SET UP
	MOV	CH,LOW 0	;GET READY FOR DAD
	ADD	BX,CX		;NOW INDEXING INTO STRING
	SUB	AL,CL		;MAKE LENGTH OF STRING S1$ RIGHT
	MOV	CH,AL		;SAVE LENGTH OF 1ST STRING IN [B]
	PUSH	CX		;SAVE COUNTER, OFFSET
	PUSH	DX		;PUT 2ND DESC (S2$) ON STACK
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;GET 2ND DESC. POINTER
	MOV	CL,BYTE PTR [BX]	;SET UP LENGTH
	INC	BX		;BUMP POINTER
	MOV	DX,[BX]		;GET FIRST BYTE OF ADDRESS
	POP	BX		;RESTORE POINTER FOR 1ST STRING

CHK1:	PUSH	BX		;SAVE POSITION IN SEARCH STRING
	PUSH	DX		;SAVE START OF SUBSTRING
	PUSH	CX		;SAVE WHERE WE STARTED SEARCH
CHK:	MOV	SI,DX
	MOV	AL,[SI]		;GET CHAR FROM SUBSTRING
	CMP	AL,BYTE PTR [BX]	; = CHAR POINTER TO BY [H,L]
	JNZ	SHORT OHWELL	;NO
	INC	DX		;BUMP COMPARE POINTER
	DEC	CL		;END OF SEARCH STRING?
	JZ	SHORT GOTSTR	;WE FOUND IT!
	INC	BX		;BUMP POINTER INTO STRING BEING SEARCHED
				;DECREMENT LENGTH OF SEARCH STRING
	DEC	CH
	JNZ	SHORT CHK	;END OF STRING, YOU LOSE
RETZER:	POP	DX		;GET RID OF POINTERS
	POP	DX		;GET RID OF GARB
	POP	CX		;LIKE SO
RETZR1:	POP	DX
	XOR	AL,AL		;GO TO SNGFLT.
	RET			;RETURN

GOTSTR:	POP	BX
	POP	DX		;GET RID OF GARB
	POP	DX		;GET RID OF EXCESS STACK
	POP	CX		;GET COUNTER, OFFSET
	MOV	AL,CH		;GET ORIGINAL SOURCE COUNTER
	SUB	AL,BH		;SUBTRACT FINAL COUNTER
	ADD	AL,CL		;ADD ORIGINAL OFFSET (N1%)
	INC	AL		;MAKE OFFSET OF ZERO = POSIT 1
	RET			;DONE


OHWELL:	POP	CX
	POP	DX		;POINT TO START OF SUBSTRING
	POP	BX		;GET BACK WHERE WE STARTED TO COMPARE
	INC	BX		;AND POINT TO NEXT CHAR
				;DECR. # CHAR LEFT IN SOURCE STRING
	DEC	CH
	JNZ	SHORT CHK1	;TRY SEARCHING SOME MORE
	JMP	SHORT RETZR1	;END OF STRING, RETURN 0

	PAGE	
	SUBTTL STRING FUNCTIONS - LEFT HAND SIDE MID$
LHSMID:	CALL	SYNCHR
	DB	OFFSET "("	;MUST HAVE ( 
	CALL	PTRGET		;GET A STRING VAR
	CALL	CHKSTR		;MAKE SURE IT WAS A STRING
	PUSH	BX		;SAVE TEXT POINTER
	PUSH	DX		;SAVE DESC. POINTER
	XCHG	BX,DX		;PUT DESC. POINTER IN [H,L]
	INC	BX		;MOVE TO ADDRESS FIELD
	MOV	DX,[BX]		;GET ADDRESS OF LHS IN [D,E]
	MOV	BX,STREND	;SEE IF LHS STRING IS IN STRING SPACE
	CMP	BX,DX		;BY COMPARING IT WITH STKTOP
	JB	SHORT NCPMID	;IF ALREADY IN STRING SPACE
				;DONT COPY.
DSEG	SEGMENT PUBLIC 'DATASG'
	EXTRN	TXTTAB:WORD
DSEG	ENDS
	MOV	BX,TXTTAB
	CMP	BX,DX		;Is this a fielded string?
	JAE	SHORT NCPMID	;Yes, Don't copy!!
NCP1:	POP	BX		;GET BACK DESC. POINTER
	PUSH	BX		;SAVE BACK ON STACK
	CALL	STRCPY		;COPY THE STRING LITERAL INTO STRING SPACE
	POP	BX		;GET BACK DESC. POINTER
	PUSH	BX		;BACK ON STACK AGAIN
	CALL	VMOVE		;MOVE NEW DESC. INTO OLD SLOT.
NCPMID:	POP	BX		;GET DESC. POINTER
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;GET TEXT POINTER TO [H,L] DESC. TO STACK
	CALL	SYNCHR
	DB	OFFSET 54O	;MUST HAVE COMMA
	CALL	GETBYT		;GET ARG#2 (OFFSET INTO STRING)
	OR	AL,AL		;MAKE SURE NOT ZERO
	JNZ	SHORT ??L010
	JMP	FCERR		;BLOW HIM UP IF ZERO
??L010:
	PUSH	AX		;SAVE ARG#2 ON STACK
	MOV	AL,BYTE PTR [BX]	;RESTORE CURRENT CHAR
	CALL	MIDRST		;USE MID$ CODE TO EVALUATE POSIBLE THIRD ARG.
	PUSH	DX		;SAVE THIRD ARG ([E]) ON STACK
				;MUST HAVE = SIGN
	CALL	FRMEQL		;EVALUATE RHS OF THING.
	PUSH	BX		;SAVE TEXT POINTER.
	CALL	FRESTR		;FREE UP TEMP RHS IF ANY.
	XCHG	BX,DX		;PUT RHS DESC. POINTER IN [D,E]
	POP	BX		;TEXT POINTER TO [H,L]
	POP	CX		;ARG #3 TO C.
	POP	AX		;ARG #2 TO A.
	MOV	CH,AL		;AND [B]
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;GET LHS DESC. POINTER TO [H,L]
				;TEXT POINTER TO STACK
	PUSH	BX		;SAVE TEXT POINTER
	MOV	BX,OFFSET POPHRT	;GET ADDR TO RETURN TO
	POP	SI		;XTHL
	XCHG	SI,BX
	PUSH	SI		;SAVE ON STACK & GET BACK TXT PTR.
	MOV	AL,CL		;GET ARG #3
	OR	AL,AL		;SET CC'S
	JNZ	SHORT $+3
	RET			;IF ZERO, DO NOTHING
	MOV	AL,BYTE PTR [BX]	;GET LENGTH OF LHS
	SUB	AL,CH		;SEE HOW MANY CHARS IN EMAINDER OF STRING
	JAE	SHORT ??L011
	JMP	FCERR		;CANT ASSIGN PAST LEN(LHS)!
??L011:
	INC	AL		;MAKE PROPER COUNT
	CMP	AL,CL		;SEE IF # OF CHARS IS .GT. THIRD ARG
	JB	SHORT BIGLEN	;IF SO, DONT TRUNCATE
	MOV	AL,CL		;TRUNCATE BY USING 3RD ARG.
BIGLEN:	MOV	CL,CH		;GET OFFSET OF STRING IN [C]
	DEC	CL		;MAKE PROPER OFFSET
	MOV	CH,LOW 0	;SET UP [B,C] FOR LATER DAD B.
	PUSH	DX		;SAVE [D,E]
	INC	BX		;POINTER TO ADDRESS FIELD.
	MOV	DL,BYTE PTR [BX]	;GET LOW BYTE IN [E]
	INC	BX		;BUMP POINTER
	MOV	BH,BYTE PTR [BX]	;GET HIGH BYTE IN [H]
	MOV	BL,DL		;NOW COPY LOW BYTE BACK TO [L]
	ADD	BX,CX		;ADD OFFSET
	MOV	CH,AL		;SET COUNT OF LHS IN [B]
	POP	DX		;RESTORE [D,E]
	XCHG	BX,DX		;MOVE RHS. DESC. POINTER TO [H,L]
	MOV	CL,BYTE PTR [BX]	;GET LEN(RHS) IN [C]
	INC	BX		;MOVE POINTER
	MOV	BX,[BX]		;GET LOW BYTE OF ADDRESS IN [A]
	XCHG	BX,DX		;ADDRESS OF RHS NOW IN [D,E]
	MOV	AL,CL		;IS RHS NULL?
	OR	AL,AL		;TEST
	JNZ	SHORT $+3
	RET			;THEN ALL DONE.
; NOW ALL SET UP FOR ASSIGNMENT.
; [H,L] = LHS POINTER
; [D,E] = RHS POINTER
; C = LEN(RHS)
; B = LEN(LHS)

MID$LP:	MOV	SI,DX
	MOV	AL,[SI]		;GET BYTE FROM RHS.
	MOV	BYTE PTR [BX],AL	;STORE IN LHS
	INC	DX		;BUMP RHS POINTER
	INC	BX		;BUMP LHS POINTER.
	DEC	CL		;BUMP DOWN COUNT OF RHS.
	JNZ	SHORT $+3
	RET			;IF ZERO, ALL DONE.
				;IF LHS ENDED, ALSO DONE.
	DEC	CH
	JNZ	SHORT MID$LP	;IF NOT DONE, MORE COPYING.
	RET			;BACK TO NEWSTT

MIDRST:	MOV	DL,LOW 255	;IF TWO ARG GUY, TRUNCATE.
	CMP	AL,LOW ")"
	JZ	SHORT MID2	;[E] SAYS USE ALL CHARS
				;IF ONE ARGUMENT THIS IS CORRECT
	CALL	SYNCHR
	DB	OFFSET 44	;COMMA? MUST DELINEATE 3RD ARG.
	CALL	GETBYT		;GET ARGUMENT  IN  [E]
MID2:	CALL	SYNCHR
	DB	OFFSET ")"	;MUST BE FOLLOWED BY )
	RET			;ALL DONE.

	SUBTTL FRE  FUNCTION AND INTEGER TO FLOATING  ROUTINES
FRE:
	CALL	GETYPR
	JZ	SHORT ??L012
	JMP	CLCDIF
??L012:
	CALL	FREFAC		;FREE UP ARGUMENT AND SETUP
				;TO GIVE FREE STRING SPACE
	CALL	GARBA2		;DO GARBAGE COLLECTION
CLCDIF:	MOV	DX,STREND
	MOV	BX,FRETOP	;TOP OF FREE AREA
	JMP	GIVDBL

CSEG	ENDS
	END