Re: variable.(key) what is?

[Andrew Janke]

On 12/19/19 2:21 PM, shivax via Help list for GNU Octave wrote:
> hi, i see in example code the .()  after variable 
> 
> Example:
> 
> function v = mod09_05_state(key, val)
>   persistent state;
>   if (nargin == 0)  
>     % Return the entire struct
>      printf("0 \n" );
>     v = state;
>   elseif (nargin == 1)
>     % Return a particular field from the struct
>     printf("1 \n" );
>     v = state.(key);
>   elseif (nargin == 2)
>       printf("2 \n" );
>     % Set a key value (key must be a string)
>     state.(key) = val;
>     v = val;
>   end
> end
> 
> what is  .(key)? i dont find in help octave variable
> 

It's dynamic field/property access, used on structs and objects. `name =
"foo"; s.(name)` is the same as `s.foo`. Example:

>> s.foo = 42
s =
  scalar structure containing the fields:
    foo =  42

>> fieldname = "foo";
>> s.(fieldname)
ans =  42
>> s.foo
ans =  42
>>

You can also use it to make structs with weird field names (but you
probably shouldn't):

>> s.("foo bar") = 12345
s =
  scalar structure containing the fields:
    foo =  42
    foo bar =  12345

Cheers,
Andrew