This file is indexed.

/usr/share/octave/packages/symbolic-2.2.4/syms.m is in octave-symbolic 2.2.4-1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
%% Copyright (C) 2014, 2015 Colin B. Macdonald
%%
%% This file is part of OctSymPy.
%%
%% OctSymPy 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.
%%
%% This software 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 software; see the file COPYING.
%% If not, see <http://www.gnu.org/licenses/>.

%% -*- texinfo -*-
%% @documentencoding UTF-8
%% @deftypefn  {Function File} {} syms @var{x}
%% @deftypefnx {Function File} {} syms @var{x} @var{y} @dots{}
%% @deftypefnx {Function File} {} syms @var{f(x)}
%% @deftypefnx {Function File} {} syms @var{x} @var{asm}
%% @deftypefnx {Function File} {} syms @var{x} @var{asm} @var{asm2} @dots{}
%% @deftypefnx {Function File} {} syms
%% Create symbolic variables and symbolic functions.
%%
%% This is a convenience function.  For example:
%% @example
%% >> syms x y z
%% @end example
%% instead of:
%% @example
%% >> x = sym('x');
%% >> y = sym('y');
%% >> z = sym('z');
%% @end example
%%
%% The last arguments can provide one or more assumptions (type or
%% restriction) on the variable (@pxref{sym}).
%% @example
%% >> syms x y z positive
%% >> syms n positive even
%% @end example
%%
%% Symfuns represent abstract or concrete functions.  Abstract
%% symfuns can be created with @code{syms}:
%% @example
%% >> syms f(x)
%% @end example
%% If @code{x} does not exist in the callers workspace, it
%% is created as a @strong{side effect} in that workspace.
%%
%% Called without arguments, @code{syms} displays a list of
%% all symbolic functions defined in the current workspace.
%%
%% Caution: On Matlab, you may not want to use @code{syms} within
%% functions.
%%   In particular, if you shadow a function name, you may get
%%   hard-to-track-down bugs.  For example, instead of writing
%%   @code{syms alpha} use @code{alpha = sym('alpha')} in functions.
%%   [https://www.mathworks.com/matlabcentral/newsreader/view_thread/237730]
%%
%% @seealso{sym}
%% @end deftypefn

%% Author: Colin B. Macdonald
%% Keywords: symbolic, symbols, CAS

function syms(varargin)

  %% No inputs
  %output names of symbolic vars
  if (nargin == 0)
    S = evalin('caller', 'whos');
    disp('Symbolic variables in current scope:')
    for i=1:numel(S)
      %S(i)
      if strcmp(S(i).class, 'sym')
        disp(['  ' S(i).name])
      elseif strcmp(S(i).class, 'symfun')
        % FIXME improve display of symfun
        disp(['  ' S(i).name ' (symfun)'])
      end
    end
    return
  end



  %% Find assumptions
  valid_asm = assumptions('possible');
  last = -1;
  doclear = false;
  for n=1:nargin
    assert(ischar(varargin{n}), 'syms: expected string inputs')
    if (ismember(varargin{n}, valid_asm))
      if (last < 0)
        last = n - 1;
      end
    elseif (strcmp(varargin{n}, 'clear'))
      doclear = true;
      if (last < 0)
        last = n - 1;
      else
        warning('syms: should not combine "clear" with other assumptions')
      end
      if (n ~= nargin)
        error('syms: "clear" should be the final argument')
      end
    elseif (last > 0)
      error('syms: cannot have symbols after assumptions')
    end
  end

  if (last < 0)
    asm = {};
    exprs = varargin;
  elseif (last == 0)
    error('syms: cannot have only assumptions w/o symbols')
  else
    asm = varargin((last+1):end);
    exprs = varargin(1:last);
  end



  % loop over each input
  for i = 1:length(exprs)
    expr = exprs{i};

    % look for parenthesis: check if we're making a symfun
    if (isempty (strfind (expr, '(') ))  % no
      assert(isvarname(expr)); % help prevent malicious strings
      if (doclear)
        % We do this here instead of calling sym() because sym()
        % would modify this workspace instead of the caller's.
        newx = sym(expr);
        assignin('caller', expr, newx);
        xstr = newx.flat;
        % ---------------------------------------------
        % Muck around in the caller's namespace, replacing syms
        % that match 'xstr' (a string) with the 'newx' sym.
        %xstr = x;
        %newx = s;
        context = 'caller';
        % ---------------------------------------------
        S = evalin(context, 'whos');
        evalin(context, '[];');  % clear 'ans'
        for i = 1:numel(S)
          obj = evalin(context, S(i).name);
          [newobj, flag] = symreplace(obj, xstr, newx);
          if flag, assignin(context, S(i).name, newobj); end
        end
        % ---------------------------------------------
      else
        assignin('caller', expr, sym(expr, asm{:}))
      end

    else  % yes, this is a symfun
      assert(isempty(asm), 'mixing symfuns and assumptions not supported')
      % regex matches: abc(x,y), f(var), f(x, y, z), f(r2d2), f( x, y )
      % should not match: Rational(2, 3), f(2br02b)
      assert(~isempty(regexp(expr, '^\w+\(\s*[A-z]\w*(,\s*[A-z]\w*)*\s*\)$')), ...
             'invalid symfun expression')
      s = sym(expr);
      %vars = symvar(s)  % might re-order the inputs, instead:
      cmd = { 'f = _ins[0]'
              'return (f.func.__name__, f.args)' };
      [name, vars] = python_cmd (cmd, s);
      sf = symfun(s, vars);
      assignin('caller', name, sf);
      for i = 1:length(vars)
        v = vars{i};
        assignin('caller', v.flat, v);
      end
    end
  end
end


%!test
%! %% assumptions
%! syms x real
%! x2 = sym('x', 'real');
%! assert (isequal (x, x2))

%!test
%! %% assumptions and clearing them
%! syms x real
%! f = {x {2*x}};
%! A = assumptions();
%! assert ( ~isempty(A))
%! syms x clear
%! A = assumptions();
%! assert ( isempty(A))

%!test
%! %% matlab compat, syms x clear should add x to workspace
%! syms x real
%! f = 2*x;
%! clear x
%! assert (~logical(exist('x', 'var')))
%! syms x clear
%! assert (logical(exist('x', 'var')))

%!error <symbols after assumptions>
%! syms x positive y

%!error <symbols after assumptions>
%! % this sometimes catches typos or errors in assumption names
%! % (if you need careful checking, use sym not syms)
%! syms x positive evne

%!warning <should not combine>
%! syms x positive clear

%!error <should be the final argument>
%! syms x clear y

%!error <cannot have only assumptions>
%! syms positive integer

%!test
%! % does not create a variable called positive
%! syms x positive integer
%! assert (logical(exist('x', 'var')))
%! assert (~logical(exist('positive', 'var')))