function [outx,xexpr,inargs,emsg] = ezfcnchk(inx,textnum,defarg)
%EZFCNCHK Version of FCNCHK for EZPLOT, EZPLOT3, etc.
%    [OUTX,XEXPR,INARGS,EMSG]=EZFCNCHK(INX) is similar to FCNCHK.  It
%    takes a single input that can be an expression, function name,
%    function handle, or inline.  It attempts to distinguish between
%    an input expression that is the identity function versus the name
%    of an M-file or builtin function.
%
%    OUTX is an inline function based on INX if INX is an expression,
%    or is the same as INX otherwise.  XEXPR is a version of INX
%    suitable for use as text on a graph.  INARGS is a cell array of
%    arguments in INX if they can be determined, or {}.  If there
%    is an error and there are four outputs, EMSG gets the error text.
%
%    [...]=EZFCNCHK(INX,TEXTNUM,DEFARG) for TEXTNUM=1 preserves things
%    like '2' as text.  TEXTNUM=0 (the default) creates an inline function
%    with a single argument.  If present, DEFARG is the name to use
%    as a default argument name if INX is a simple function name
%    as opposed to an expression that includes an argument name.

%   Copyright 1984-2004 The MathWorks, Inc.
%   $Revision: 1.4.4.4 $  $Date: 2004/08/16 01:52:17 $

if (nargout>2), inargs = {}; end
if (nargout>3)
    emsg.message = '';
    emsg.identifier = '';
    emsg = emsg(zeros(0,1)); % make sure emsg is the right dimension
end

% Remove array notation from inline functions
xexpr = inx;
if (nargout>1) & isa(inx, 'inline')
   xexpr = char(inx);
   if (length(xexpr) > 2)
      xexpr(findstr(xexpr, '.*')) = [];
      xexpr(findstr(xexpr, '.^')) = [];
      xexpr(findstr(xexpr, './')) = [];
   end
end

% Check for function vs. identity expression such as 't',
% and convert to a consistent form
outx = inx;
numonly = 0;             % indicates a numeric expression, no variables
e = 0;
if (ischar(inx))
   numonly = isempty(symvar(inx));
   if (numonly & nargin>1 & textnum==1), return; end

   e = exist(inx);
   dovector = (e~=2 & e~=5) | (e==5 & numonly);
   
   % Always vectorize an inline rather than a character string,
   % because we don't want to add 'ones(size(x))' to the expression.
   if (dovector), outx = inline(inx); end
else
   dovector = isa(inx,'inline');
end
if (dovector)
   [outx,emsg] = fcnchk(outx, 'vectorized');
else
   [outx,emsg] = fcnchk(outx);
end

% Display error unless caller is going to deal with it
if (nargout<4), error(emsg); end

% Get function expression for label, if not already done
if (isa(outx,'function_handle')), xexpr = func2str(outx); end

% Sometimes we can check the number of inputs expected
if (nargout>2)
   if (isa(outx, 'inline'))
      inargs = argnames(outx);
      
      % Some inputs such as 'sin' will become inline functions with
      % an argument 'x' that does not really appear in the input.
      % In that case, give the argument an "anonymous" name.
      if (ischar(inx) & isequal(inargs,{'x'}) & ...
          ~ismember({'x'},symvar(inx)))
         inargs = {''};
      end
   elseif isa(outx,'function_handle')
      if ismember('(',xexpr) && ismember(')',xexpr)
         % For function handles that are anonymous functions, get the
         % names of the args and define a reasonable expression
         A = find(xexpr=='(',1);
         B = find(xexpr==')',1);
         inargs = strtrim(strread(xexpr(A+1:B-1),'%s','delimiter',','));
         xexpr = strtrim(xexpr(B+1:end));
      end
   elseif (ischar(outx) & ((e==2) | (e==5 & ~isempty(symvar(outx)))))
      if (e==2)
         k = nargin(outx);
      else
         k = 1;  % assume one argument for builtin function
      end
      if (k>=1), inargs{1} = ''; end
      if (k>=2), inargs{2} = ''; end
      if (nargin>2)
         xexpr = [xexpr '(' defarg ')'];
      elseif (k==2)
         xexpr = [xexpr '(x,y)'];
      else
         xexpr = [xexpr '(x)'];
      end
   end
end