Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / symbolic-1.1.0 / findsym.m

diff --git a/octave_packages/symbolic-1.1.0/findsym.m b/octave_packages/symbolic-1.1.0/findsym.m
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+## Copyright (C) 2003 Willem J. Atsma <watsma@users.sf.net>
+##
+## 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, 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 -*-
+## @deftypefn {Function File} {@var{vars} =} findsym (@var{f}, @var{n})
+## Find symbols in expression @var{f} and return them comma-separated in
+## string @var{vars}. The symbols are sorted in alphabetic order. If @var{n}
+## is specified, the @var{n} symbols closest to "x" are returned.
+##
+## Example:
+## @example
+## symbols
+## x     = sym ("x");
+## y     = sym ("y");
+## f     = x^2+3*x*y-y^2;
+## vars  = findsym (f);
+## vars2 = findsym (f,1);
+## @end example
+##
+## This is intended for m****b compatibility, calls findsymbols().
+## @seealso{findsymbols}
+## @end deftypefn
+
+function VARS = findsym(F,Nout)
+
+  symlist = findsymbols(F);
+  Nlist = length(symlist);
+  if Nlist==0
+    warning("No symbols were found.")
+    VARS = "";
+    return
+  endif
+
+  if exist("Nout")!=1
+    VARS = disp(symlist{1});
+    for i=2:Nlist
+      VARS = [VARS "," disp(symlist{i})];
+    endfor
+    return
+  else
+    ## If Nout is specified, sort anew from x.
+    symstrings = disp(symlist{1});
+    for i=2:Nlist
+      symstrings = [symstrings ; disp(symlist{i})];
+    endfor
+
+    symasc = toascii(symstrings);
+
+    if Nlist<Nout
+      warning("Asked for %d, variables, only %d found.",Nout,Nlist);
+      Nout=Nlist;
+    endif
+    symasc(:,1) = abs(toascii("x")-symasc(:,1));
+
+    ## Sort by creating an equivalent number for each entry
+    Nc = length(symasc(1,:));
+    powbase=zeros(Nc,1); powbase(Nc)=1;
+    for i=(Nc-1):-1:1
+      powbase(i) = powbase(i+1)*128;
+    endfor
+    [xs,I]=sort(symasc*powbase);
+
+    VARS = deblank(symstrings(I(1),:));
+
+    for i=2:Nout
+      VARS = [VARS "," deblank(symstrings(I(i),:))];
+    endfor
+
+  endif
+endfunction
+
+%!test
+%! symbols
+%! x=sym("x"); y=sym("y"); f=x^2+3*x*y-y^2;
+%! vars = findsym (f);
+%! assert(vars, 'x,y');
+%! vars2 = findsym (f,1);
+%! assert(vars2, 'x');