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bi2de.m

## Copyright (C) 2001 Laurent Mazet
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; If not, see <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {@var{d} = } bi2de (@var{b})
## @deftypefnx {Function File} {@var{d} = } bi2de (@var{b},@var{p})
## @deftypefnx {Function File} {@var{d} = } bi2de (@var{b},@var{p},@var{f})
##
## Convert bit matrix to a vector of integers
##
## Each row of the matrix @var{b} is treated as a single integer represented
## in binary form. The elements of @var{b}, must therefore be '0' or '1' 
##
## If @var{p} is defined then it is treated as the base of the decomposition
## and the elements of @var{b} must then lie between '0' and 'p-1'.
##
## The variable @var{f} defines whether the first or last element of @var{b}
## is considered to be the most-significant. Valid values of @var{f} are
## 'right-msb' or 'left-msb'. By default @var{f} is 'right-msb'.
## @end deftypefn
## @seealso{de2bi}

## 2001-02-02
##   initial release
## 2003-02-02
##   add orientation of b and help in texinfo

function d = bi2de (b, p, f)

  switch (nargin)
    case 1,
      p = 2;
      f = 'right-msb';
     case 2,
      if (ischar(p))
        f = p;
        p = 2;
      else
        f = 'right-msb';
      endif
     case 3,
      if (ischar(p))
        tmp = f;
        f = p;
        p = tmp;
      endif
   otherwise
      error ("usage: d = bi2de (b, [p])");
  endswitch

  if ( any (b (:) < 0) || any (b (:) > p - 1) )
    error ("bi2de: d must only contain value in [0, p-1]");
  endif

  if (strcmp(f,'left-msb'))
    b = b(:,size(b,2):-1:1);
  elseif (!strcmp(f,'right-msb'))
    error("bi2de: unrecognized flag");
  endif

  if (length (b) == 0)
    d = [];
  else
    d = b * ( p .^ [ 0 : (columns(b)-1) ]' );
  endif

endfunction;

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