Locates a specified portion of a character string and returns as
    an integer the offset of the first character. (An offset is the
    position of a character or a substring relative to the beginning
    of the string. The first character in a string is always offset
    position 0 from the beginning of the string.)

    If the substring is not found, F$LOCATE returns the length (the
    offset of the last character in the character string plus one) of
    the searched string.

    Format

      F$LOCATE(substring,string)