01/04/85  reverse_substr, rvsubstr

Syntax as a command:  rvsubstr STR I {N}


Syntax as an active function:  [rvsubstr STR I {N}]


Function:  performs the same function as the substr command/active
function, but counts characters from right to left.  The returned
string has its characters in the same order as the input string.


Notes:  The active function returns that portion of STR starting with
the character in position I (the characters in the string being numbered
from right to left starting with one) and continuing for N characters
(where I and N are decimal integers; I must be greater than zero and N
must be greater than or equal to zero).  If N is omitted, the remained
of STR is returned.  If I is greater than the length of STR, the null
string is returned.  If N is greater than the remainder of STR, the
remainder is returned.

   [reverse_substr STR I {N}]
is the same as--
   [reverse [substr [reverse STR] I {N}]]


Examples:
(! marks user input)

 ! reverse_substr abcdefg 2 3
   def
 ! reverse_substr frobozz 4
   frob
 ! reverse_substr spatula 5 4
   spa


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Historical Background

This edition of the Multics software materials and documentation is provided and donated
to Massachusetts Institute of Technology by Group BULL including BULL HN Information Systems Inc. 
as a contribution to computer science knowledge.  
This donation is made also to give evidence of the common contributions of Massachusetts Institute of Technology,
Bell Laboratories, General Electric, Honeywell Information Systems Inc., Honeywell BULL Inc., Groupe BULL
and BULL HN Information Systems Inc. to the development of this operating system. 
Multics development was initiated by Massachusetts Institute of Technology Project MAC (1963-1970),
renamed the MIT Laboratory for Computer Science and Artificial Intelligence in the mid 1970s, under the leadership
of Professor Fernando Jose Corbato. Users consider that Multics provided the best software architecture 
for managing computer hardware properly and for executing programs. Many subsequent operating systems 
incorporated Multics principles.
Multics was distributed in 1975 to 2000 by Group Bull in Europe , and in the U.S. by Bull HN Information Systems Inc., 
as successor in interest by change in name only to Honeywell Bull Inc. and Honeywell Information Systems Inc. .

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Permission to use, copy, modify, and distribute these programs and their documentation for any purpose and without
fee is hereby granted,provided that the below copyright notice and historical background appear in all copies
and that both the copyright notice and historical background and this permission notice appear in supporting
documentation, and that the names of MIT, HIS, BULL or BULL HN not be used in advertising or publicity pertaining
to distribution of the programs without specific prior written permission.
    Copyright 1972 by Massachusetts Institute of Technology and Honeywell Information Systems Inc.
    Copyright 2006 by BULL HN Information Systems Inc.
    Copyright 2006 by Bull SAS
    All Rights Reserved