function [index] = binary_to_index(length,value)
% binary_to_index.m
%
% Usage:
%   index = binary_to_index(5, 2)
%   bitstring = index_to_bitstring(index)
% returns the 5 bits
%   bitstring = [  0     0     0     1     0 ]
% (5 bits, with binary value of 2).
% Usage:
%   indexes = binary_to_index( [3 2 2], [7 0 2] )
%   print_bitstrings(indexes)
% returns
%   111
%   00
%   10
% which are bitstrings of length 3, 2, 2 respectively,
% with values of 7, 0, and 2 respectively.
% See also INDEX_TO_BITSTRING, PRINT_BITSTRINGS, BITSTRING_TO_INDEX.

   % In C, I would probably use standard binary notation
   % with seperate length.code variables
   % and say something like
   % current_code(longest_code_length) = 0;
   %
   % Here I use Kieffer's notation,
   % which combines length and code into a single 'index' value.
   % and any other bitstring of length N
   % is represented by the
   % value of that bitstring (interpreted as standard binary)
   % plus the value that represents a bistring of N zeros.


% Change Log:
% 1999-06-25:DAV: David Cary <d.cary at ieee.org> started

% Unnecessarily restrictive -- the algorithm
% can handle length = 53 when value = 0 or value = 1.
% IEEE754 double precision can handle integers exactly
% up to (but not including) 2^53+1. See BITMAX.
if( 53 <= max(length(:)) ),
   error('Sorry, this is too big for me to handle.')
end;

% ASSERT( V < 2.^L )
index = 2.^length + (value-1);

% end binary_to_index.m