[gPXE-devel] More Scripting Discussion

[Shao Miller]

Lynus Vaz wrote:
> Hi Shao,

Hello Lynus!

> I think it would be nice to have at least equal and not-equal 
> operators in <condition>, to check variable values.

Discussion with Joshua Oreman revealed an opinion that operators could 
be used as part of the expansion syntax.  I believe that your code did 
something like this, too.  ${ val1 != val2 }.  I'm not sure if operators 
belong in the 'if' command or not, but they certainly would be handy to 
have!  I'm sure they would most often be used with 'if'.

> So does 'deferred execution' mean stopping code execution till the 
> label is found? I found it a bit difficult to follow the terms 
> yesterday. 

Basically a strategy was to store a routine's offset in the script as 
soon as the routine was passed by, but the routine would not be 
executed.  Code after of the routine's terminator would be executed.  If 
executed code issued a 'goto', it would jump to the routine and execute 
the routine's code.  A challenge here was that only routines which has 
already been passed by were available to 'goto', which meant all 
routines had to be "declared" before being used.  This made the if-else 
construct particularly tricky.  Anyway, this strategy seems unpleasant 
and I've abandoned it.

A more pleasant strategy is for all routines to be available at all 
times, and to simply execute every line of code as it is passed.  Stefan 
and I both have patches which do this, with different implementations.

Thanks for your consideration, Lynus. :)

- Shao Miller