Puzzled about scope/existence of globals

[John W. Eaton]

On 22-Nov-2003, Glenn Golden <address@hidden> wrote:

| Given the function foo(), defined as
| 
|     function foo()
|       global g;
|       exist("g", "var")
|     endfunction
| 
| I found the following to be surprising:
| 
|     1>   foo
|     ans = 0                   # ok

This can happen in versions of Octave before 2.1.51 because global
variables are not initialized by default.  You can change this
behavior with the built-in variables default_global_variable_value and
initialize_global_variables.  In 2.1.51 and later, these variables are
gone and for compatibility with Matlab, Octave always initializes
global variables to [] (unless you provide your own initializer in the
global statement).

|     2>   global g
| 
|     3>   g.barf = 1;
| 
|     4>   foo
|     ans = 1                   # ok
| 
|     5>   clear g 
| 
|     6>   whos g       
|                               # ok
|     7>   foo
|     ans = 1                   # huh?

You cleared the link to the global g in the top-level workspace, but
not in the function foo, which still exists.  Clear foo, and g should
really go away (unless there is some other function that still has it
as a global).

jwe



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