EVAL EVAL Evaluate a String

Usage

The eval function evaluates a string.  The general syntax
for its use is

   eval(s)

where s is the string to evaluate.  If s is an expression
(instead of a set of statements), you can assign the output
of the eval call to one or more variables, via

   x = eval(s)
   [x,y,z] = eval(s)


Another form of eval allows you to specify an expression or
set of statements to execute if an error occurs.  In this 
form, the syntax for eval is

   eval(try_clause,catch_clause),

or with return values,

   x = eval(try_clause,catch_clause)
   [x,y,z] = eval(try_clause,catch_clause)

These later forms are useful for specifying defaults.  Note that
both the try_clause and catch_clause must be expressions,
as the equivalent code is

  try
    [x,y,z] = try_clause
  catch
    [x,y,z] = catch_clause
  end

so that the assignment must make sense in both cases.