/usr/share/freemat/toolbox/func/symvar.m is in freemat-data 4.0-5.
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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 | % SYMVAR SYMVAR Find Symbolic Variables in an Expression
%
% Usage
%
% Finds the symbolic variables in an expression. The syntax for its
% use is
%
% syms = symvar(expr)
%
% where expr is a string containing an expression, such as
% 'x^2 + cos(t+alpha)'. The result is a cell array of strings
% containing the non-function identifiers in the expression. Because
% they are usually not used as identifiers in expressions, the strings
% 'pi','inf','nan','eps','i','j' are ignored.
% Copyright (c) 2002-2007 Samit Basu
% Licensed under the GPL
function syms = symvar(expr)
if (isempty(expr))
syms = cell(0,0);
return;
end
if (~isstr(expr))
syms = cell(0,1);
return;
end
ignore = {'pi','inf','nan','eps','i','j'};
tsyms = regexp(char(expr),'(\b[a-zA-Z]\w*\b)(?!\s*\()','tokens');
tsyms = unique([tsyms{:}]);
syms = cell(0,1);
for i = 1:numel(tsyms)
if (~any(strcmp(tsyms{i},ignore)))
syms = [syms;{tsyms{i}}];
end
end
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