index(3I)

NAME
     INDEX - Determines the starting location of a character substring in a
     string

SYNOPSIS
     INDEX ([STRING=]string, [SUBSTRING=]substring [,[BACK=]back])

STANDARDS
     Fortran

DESCRIPTION
     The INDEX intrinsic function returns the starting position of a
     substring within a string from either the right or left end of the
     string.  It accepts the following arguments:

     string    Must be of type character.

     substring Must be of type character.

     back      Must be of type logical.  If omitted, a value of false is
               assumed.  If present with a value of true, the search begins
               at the end of string.  This argument is not accepted by the
               MIPSpro Fortran 77 compiler.

     INDEX is an elemental function.  The name of this intrinsic can be
     passed as an argument.

NOTES
     When the INDEX intrinsic function is passed as an actual argument, it
     must be called with only the first two arguments in the routine that
     calls the passed-in function.

RETURN VALUES
     The back argument can affect the return value as follows:

     * If back is absent or is present with the value FALSE, the INDEX
       search is relative to the left end of string.  The result is the
       minimum positive value of i, as follows:

          string ( i : i + LEN( substring ) - 1 ) = substring

       If the length of substring is 0, a value of 1 is returned.

     * If back is present with the value TRUE, the INDEX search is relative
       to the right end of string.  The result is the maximum positive
       value of the following:

          i <= LEN( string ) - LEN( substring ) + 1

       In the preceding equation, substring is as follows:

          string ( i : i + LEN( substring ) - 1 ) = substring

       If the length of substring is 0, the value returned is as follows:

          LEN( string ) + 1.

     If substring occurs more than once in string, INDEX returns the index
     to the first occurrence.

     The return value is 0 if substring is not located within string.

     The return value is 0 if the length of string is less than the length
     of substring.

EXAMPLES
     Example 1:  INDEX('FORTRAN','R') yields 3.

     Example 2:  INDEX('FORTRAN','R',BACK=.TRUE.) yields 5.

     Example 3:  The following program returns the index I=10 for the
     substring SUPERCOMPUTER:

          PROGRAM INDEX1
          CHARACTER*22 A
          CHARACTER*13 B
          A = 'CRAY T90 SUPERCOMPUTER'
          B = 'SUPERCOMPUTER'
          I = INDEX(A,B)
          PRINT *, I
          STOP
          END