Section: Inspection Functions
y = exist(item,kind)
where item is a string containing the name of the item
to look for, and kind is a string indicating the type 
of the search.  The kind must be one of 
'builtin' checks for built-in functions
 'dir' checks for directories
 'file' checks for files
 'var' checks for variables
 'all' checks all possibilities (same as leaving out kind)
 kind specification out, in which case
the calling syntax is
y = exist(item)
The return code is one of the following:
item does not exist
 item is a variable in the workspace
 item is an M file on the search path, a full pathname
 to a file, or an ordinary file on your search path
 item is a built-in FreeMat function
 item is a directory
 1.10, exist used a different notion
of existence for variables: a variable was said to exist if it 
was defined and non-empty.  This test is now performed by isset.
exist function.  Note that generally exist
is used in functions to test for keywords.  For example,
  function y = testfunc(a, b, c)
  if (~exist('c'))
    % c was not defined, so establish a default
    c = 13;
  end
  y = a + b + c;
An example of exist in action.
--> a = randn(3,5,2)
a = 
(:,:,1) = 
    0.0744   -0.7000   -1.8022   -0.0255   -0.2933 
   -0.0152   -0.5401   -0.2030   -0.5437    0.9261 
   -0.4359   -1.2334    0.5156    0.0821   -0.5065 
(:,:,2) = 
    0.7408    0.6302   -0.2798    0.7279    1.7674 
    0.9063   -1.7321   -0.8851   -0.4091   -0.5516 
    1.4880    0.5030    0.6747   -0.5492    1.1867 
--> b = []
b = 
  []
--> who
  Variable Name       Type   Flags             Size
              a    double                    [3 5 2]
              b    double                    [0 0]
--> exist('a')
ans = 
 1 
--> exist('b')
ans = 
 1 
--> exist('c')
ans = 
 0