[OpenBIOS] Fwd: [PATCH] Adds local variable support to OpenBIOS.

[Tarl Neustaedter]

On 2012-Aug-31 09:50 , Programmingkid wrote:
>
> Are you saying my-variable is better than myVariable?

Yes.

> How do global variables get you in trouble in recursion? Do you have 
> an example?

Not off-hand, we learn to avoid doing that. To construct one - let's 
take a method doing recursion properly, and break it:

\ Correct way, using stack manipulation
: fibonacci ( fib -- return ) recursive
    dup 2 >= if                 ( fib )
       dup 1- fibonnaci         ( fib fib-1 )
       swap 2 - fibonnaci       ( fib-1 fib-2 )
       +                        ( fib )
    then                        ( fib )
;

\ Incorrect way - using variable "fib", which will get overwritten 
during recursion
0 value fib;
: fibonnaci ( fib -- return ) recursive
    to fib \ to avoid stack manipulation
    fib 2 < if
       fib exit
    then
    fib 1- fibonnaci           ( fib-1)
    fib 2 - fibonnaci          ( fib-1 fib-2 )
    +                          ( fib )
;

>
> I am not familiar with this alarm level. Could you explain what it is?

In IEEE 1275, you can set an "alarm" for a device. This will be called 
asynchronously when the condition in question triggers (usually a timer 
expiring). If you were in the middle of something else using global 
variables, you can get in trouble if those global variables area also 
used in the alarm code. The Serial driver for openboot uses alarms, for 
example.

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