## Copyright (C) 1993-2012 John W. Eaton
##
## This file is part of Octave.
##
## Octave 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 3 of the License, or (at
## your option) any later version.
##
## Octave 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 Octave; see the file COPYING.  If not, see
## <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn  {Function File} {} num2str (@var{x})
## @deftypefnx {Function File} {} num2str (@var{x}, @var{precision})
## @deftypefnx {Function File} {} num2str (@var{x}, @var{format})
## Convert a number (or array) to a string (or a character array).  The
## optional second argument may either give the number of significant
## digits (@var{precision}) to be used in the output or a format
## template string (@var{format}) as in @code{sprintf} (@pxref{Formatted
## Output}).  @code{num2str} can also handle complex numbers.  For
## example:
##
## @example
## @group
## num2str (123.456)
##      @result{} "123.46"
##
## num2str (123.456, 4)
##      @result{} "123.5"
##
## s = num2str ([1, 1.34; 3, 3.56], "%5.1f")
##      @result{} s =
##         1.0  1.3
##         3.0  3.6
## whos s
##      @result{}
##       Attr Name        Size                     Bytes  Class
##       ==== ====        ====                     =====  =====
##            s           2x8                         16  char
##
## num2str (1.234 + 27.3i)
##      @result{} "1.234+27.3i"
## @end group
## @end example
##
## The @code{num2str} function is not very flexible.  For better control
## over the results, use @code{sprintf} (@pxref{Formatted Output}).
## Note that for complex @var{x}, the format string may only contain one
## output conversion specification and nothing else.  Otherwise, you
## will get unpredictable results.
## @seealso{sprintf, int2str, mat2str}
## @end deftypefn

## Author: jwe

function retval = num2str (x, arg)

  if (nargin != 1 && nargin != 2)
    print_usage ();
  endif

  if (ischar (x))
    retval = x;
  elseif (isempty (x))
    retval = "";
  elseif (iscomplex (x))
    if (nargin == 2)
      if (ischar (arg))
        fmt = cstrcat (arg, "%-+", arg(2:end), "i");
      else
        if (isnumeric (x) && x == fix (x) && abs (x) < (10 .^ arg))
          fmt = sprintf ("%%%dd%%-+%ddi  ", arg, arg);
        else
          fmt = sprintf ("%%%d.%dg%%-+%d.%dgi", arg+7, arg, arg+7, arg);
        endif
      endif
    else
      ## Setup a suitable format string
      if (isnumeric (x) && x == fix (x) && abs (x) < 1e10)
        if (max (abs (real (x(:)))) == 0)
          dgt1 = 2;
        else
          dgt1 = ceil (log10 (max (max (abs (real (x(:)))),
                                   max (abs (imag (x(:))))))) + 2;
        endif
        dgt2 = dgt1 - (min (real (x(:))) >= 0);

        if (length (abs (x) == x) > 0)
          fmt = sprintf("%%%dg%%+-%dgi  ", dgt2, dgt1);
        else
          fmt = sprintf("%%%dd%%+-%ddi  ", dgt2, dgt1);
        endif
      elseif (isscalar (x))
        fmt = "%.6g%-+.6gi";
      else
        fmt = "%11.6g%-+11.6gi";
      endif
    endif

    ## Manipulate the complex value to have real values in the odd
    ## columns and imaginary values in the even columns.
    sz = size (x);
    nc = sz(2);
    nd = ndims (x);
    perm = fix ([1:0.5:nc+0.5]);
    perm(2:2:2*nc) = perm(2:2:2*nc) + nc;
    idx = repmat ({':'}, nd, 1);
    idx{2} = perm;
    x = horzcat (real (x), imag (x));
    x = x(idx{:});

    fmt = cstrcat (deblank (repmat (fmt, 1, nc)), "\n");
    tmp = sprintf (fmt, permute (x, [2, 1, 3:nd]));

    ## Put the "i"'s where they are supposed to be.
    while (true)
      tmp2 = strrep (tmp, " i\n", "i\n");
      if (length (tmp) == length (tmp2))
        break;
      else
        tmp = tmp2;
      endif
    endwhile
    while (true)
      tmp2 = strrep (tmp, " i", "i ");
      if (tmp == tmp2)
        break;
      else
        tmp = tmp2;
      endif
    endwhile

    tmp(length (tmp)) = "";
    retval = char (strtrim (strsplit (tmp, "\n")));
  else
    if (nargin == 2)
      if (ischar (arg))
        fmt = arg;
      else
        if (isnumeric (x) && x == fix (x) && abs (x) < (10 .^ arg))
          fmt = sprintf ("%%%dd  ", arg);
        else
          fmt = sprintf ("%%%d.%dg", arg+7, arg);
        endif
      endif
    else
      if (isnumeric (x) && x == fix (x) && abs (x) < 1e10)
        if (max (abs (x(:))) == 0)
          dgt = 2;
        else
          dgt = floor (log10 (max (abs(x(:))))) + (min (real (x(:))) < 0) + 2;
        endif
        if (length (abs (x) == x) > 0)
          fmt = sprintf ("%%%dg  ", dgt);
        else
          fmt = sprintf ("%%%dd  ", dgt);
        endif
      elseif (isscalar (x))
        fmt = "%11.5g";
      else
        fmt = "%11.5g";
      endif
    endif
    fmt = cstrcat (deblank (repmat (fmt, 1, columns (x))), "\n");
    nd = ndims (x);
    tmp = sprintf (fmt, permute (x, [2, 1, 3:nd]));
    tmp(length (tmp)) = "";
    retval = strtrim (char (strsplit (tmp, "\n")));
  endif

endfunction

%!assert ((strcmp (num2str (123), "123") && strcmp (num2str (1.23), "1.23")));
%!assert (num2str (123.456, 4), "123.5");
%!assert (all (num2str ([1, 1.34; 3, 3.56], "%5.1f") == ["1.0  1.3"; "3.0  3.6"]));
%!assert (num2str (1.234 + 27.3i), "1.234+27.3i");
%!error num2str ();
%!error num2str (1, 2, 3);