1######################################################################## 2## 3## Copyright (C) 2008-2021 The Octave Project Developers 4## 5## See the file COPYRIGHT.md in the top-level directory of this 6## distribution or <https://octave.org/copyright/>. 7## 8## This file is part of Octave. 9## 10## Octave is free software: you can redistribute it and/or modify it 11## under the terms of the GNU General Public License as published by 12## the Free Software Foundation, either version 3 of the License, or 13## (at your option) any later version. 14## 15## Octave is distributed in the hope that it will be useful, but 16## WITHOUT ANY WARRANTY; without even the implied warranty of 17## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 18## GNU General Public License for more details. 19## 20## You should have received a copy of the GNU General Public License 21## along with Octave; see the file COPYING. If not, see 22## <https://www.gnu.org/licenses/>. 23## 24######################################################################## 25 26## -*- texinfo -*- 27## @deftypefn {} {@var{vars} =} symvar (@var{str}) 28## Identify the symbolic variable names in the string @var{str}. 29## 30## Common constant names such as @code{i}, @code{j}, @code{pi}, @code{Inf} and 31## Octave functions such as @code{sin} or @code{plot} are ignored. 32## 33## Any names identified are returned in a cell array of strings. The array is 34## empty if no variables were found. 35## 36## Example: 37## 38## @example 39## @group 40## symvar ("x^2 + y^2 == 4") 41## @result{} @{ 42## [1,1] = x 43## [2,1] = y 44## @} 45## @end group 46## @end example 47## @end deftypefn 48 49function vars = symvar (str) 50 51 vars = argnames (inline (str)); 52 ## Correct for auto-generated 'x' variable when no symvar was found. 53 if (numel (vars) == 1 && strcmp (vars{1}, "x") && ! any (str == "x")) 54 vars = {}; 55 endif 56 57endfunction 58 59 60%!assert (symvar ("3*x + 4*y + 5*cos (z)"), {"x"; "y"; "z"}) 61%!assert (symvar ("sin()^2 + cos()^2 == 1"), {}) 62%!assert (symvar ("1./x"), {"x"}) 63