C INDEX.FTN		ACR/SCF:89.1		[223,1]		11/70 IAS
C
C	31-JUL-78   H.S.MILLER
C
C==
C	FUNCTION RETURN CHARACTER POSITION OF FIRST CHARACTER 
C		IN STRING THAT MATCHES GIVEN SUBSTRING
C==
C
C++
C	INDEX FUNCTION
C	
C	THE ROUTINE IS USEFUL TO FIND THE OCCURRENCE (ACTUALLY THE
C	FIRST OCCURRENCE) OF A GIVEN SUBSTRING OF A KNOWN LENGTH
C	WITHIN A STRING BETWEEN GIVEN SUBSCRIPT POSITIONS
C
C     CALLING FORMAT IS: K=INDEX (ARRAY,FIRST,LAST,STRING,LENGTH)
C
C     K (THE RETURNED VALUE) IS 0 IF NO MATCH IS FOUND
C	                     IS THE ACTUAL SUBSCRIPT IF NO ERRORS
C			     IS -1 IF A SUBSCRIPTING ERROR OCCURS
C			           (CALLED WITH LAST < FIRST)
C	NOTE: THE LENGTH OF THE SUBSTRING MAY BE 1
C
C
	INTEGER FUNCTION INDEX (ARRAY,FIRST,LAST,STRING,IMAX)
C
C--- ENTRY POINT "INDEX" PROVIDED FOR EASY CALLS
C
	ENTRY TJU63 (ARRAY,FIRST,LAST,STRING,IMAX)
	BYTE ARRAY(1),STRING(1),SUB(100)
	INTEGER HERE, FIRST,TJU63
	CALL MOVE (STRING,1,IMAX,SUB,1)
C
C---- COMPUTE THE LENGTH OF ARRAY OF INTEREST TO DETERMINE ERROR
C
	ITER=LAST-FIRST+1
	IF (ITER.LT. 1 .OR. ITER .LT. IMAX) GO TO 6
C
C---- START FROM LEFT USING A CHAR-BY-CHAR SCAN WHERE:
C
C       MATCH IS THE POSSIBLE INDEX VALUE
C       NOW IS THE CURRENT POSITION IN THE ARRAY
C       HERE IS THE CURRENT POSITION IN THE STRING
	NOW=FIRST-1
1	MATCH=NOW+1
2	NOW=NOW+1
	HERE=1
3	IF (NOW .GT. LAST) GO TO 5
	IF (ARRAY(NOW) .NE. SUB(HERE)) GO TO 1
	HERE = HERE + 1
	IF (HERE .GT. IMAX) GO TO 4
	NOW = NOW + 1
	GO TO 3
C
C---- SUCCESS STRING BEGINS AT MATCH...
C
4	INDEX=MATCH
	TJU63=MATCH
	RETURN
C
C---- NO MATCH WITHIN GIVEN ARRAY BOUNDS
C
5	INDEX=0
	TJU63=0
	RETURN
C
C---- SUBSCRIPTING ERROR (LENGTH OF ARRAY OR STRING)
C
6	INDEX=-1
	TJU63=-1
	RETURN
	END