## Copyright (C) 2000 Daniel Calvelo
##
## 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, write to the Free Software
## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

## -*- texinfo -*-
## @deftypefn {Function File} {} dec2base (@var{n}, @var{b})
## Return a string of symbols in base @var{b} corresponding to the
## the nonnegative integer @var{n}.
##
## @example
## dec2base (123, 3)
##      @result{} "11120"
## @end example
##
## If @var{n} is a vector, return a string matrix with one row per value,
## padded with leading zeros to the width of the largest value.
##
## If @var{b} is a string then the characters of @var{b} are used as
## the symbols for the digits of @var{n}.  Space (' ') may not be used
## as a symbol.
##
## @example
## dec2base (123, "aei")
##      @result{} "eeeia"
## @end example
## @end deftypefn
##
## @seealso{base2dec, dec2bin, bin2dec, hex2dec, dec2hex}

## Author: Daniel Calvelo
## Adapted-by: Paul Kienzle
## 2001-02-02 Paul Kienzle
##    * remove third arg.; base is either a 2-36, or a string of symbols
##    * rewrite without loops
##    * use texinfo for help
## 2001-02-07 Paul Kienzle
##    * correct error message
##    * cleaner computation of required number of digits

function out = dec2base (d, base)

  if nargin != 2
    usage("dec2base (n, base)");
  endif

  if prod (size (d)) != length (d)
    error("dec2base: cannot convert matrices.");
  elseif any (d < 0 | d != fix (d))
    error("dec2base: can only convert non-negative integers.")
  endif

  symbols = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  if isstr (base)
    symbols = base;
    base = length (symbols);
    if any (diff (sort (toascii (symbols))) == 0)
      error ("dec2base: symbols representing digits must be unique.");
    endif
  elseif !is_scalar (base)
    error ("dec2base: cannot convert from several bases at once.");
  elseif base < 2 || base > length (symbols)
    error ("dec2base: base must be between 2 and 36 or a string of symbols");
  endif
  
  ## determine number of digits required to handle all numbers
  maxLen = floor ( log (max ( max (d), 1)) ./ log (base) ) + 1;
  
  ## determine digits for each number
  power = ones (length (d), 1) * (base .^ [maxLen-1 : -1 : 0] );
  d = d(:) * ones (1, maxLen);
  digits = floor (rem (d, base*power) ./ power);

  ## convert digits to symbols
  out = reshape (symbols (digits+1), size (digits));

endfunction