[chuck-users] time and truth (bug?)

[Kassen]

2008/7/24 Stephen Sinclair <radarsat1 at gmail.com>:

>
> I *was* kind of curious how you came up with this case.. ;-)
>

:¬) I'd explain more but it's a part of a interface revision of a 2500 or so
line file so that would quickly get complicated and require a lot of
explaining.... Of course anything that would run into this can also be
re-written.



>
> I wonder if it wouldn't be better to have the compile issue an error
> on something like if(second), since I don't see how it's very useful
> and could lead to bad logic on the part of the user.


Well, it's convenient for things like this;

while (beat => now)
  {
  my_drum(boom);
  }

...which is arguably bad form but very pleasant to write. I forgot who came
up with it but it's popular in the "one line ChucK crazy" game on the forum.



>  if(!now) could
> be useful for doing something only when the VM first starts up,
> however I generally think that basing your scripts on absolute time
> (relative to start of VM) is probably bad practice.  Not to mention
> that if(!now), while nice and compact, is not the most readable way to
> express that logic.


It's also invalid because "now" is not a integer and you can only do "not"
on integers. If you want that you will have to go;

if ( !((now / samp) $  int) ) <<<"yay">>>;

First the division creates a float, we cast that to integer and this int can
be inverted logically. That is, BTW, a issue with inversion, not with
evaluating if clauses as such. I use that sort of thing too toggle Gain's
used as routing gates;

Gain g;

//toggle
!( g.gain() $ int) => g.gain;

Ok, well, maybe it's a similar kind of case...  after all. Perhaps "!"
simply should return "1" for non-zero inputs.

Beware, BTW, that the above examples aren't without danger because you can
have rounding errors casting to int. I think casting to int will always
round towards 0.


>
> On second though, if(dur) could have some uses, I guess.  Not sure.
> Perhaps in calculating a delay length, while trying to avoid
> zero-delay feedback.
>

There I's use;

if (delay > 0::ms)

Because of the dengers of negative delay.

While going over Ge's paper, BTW, I sugested that we could perhaps use
"unless" as a miror of "if" since we already have "while" and "untill" which
are also mirror.images. I intended this as fun syntactic sugar (like
"untill" already is) but now that I think of it; that would nicely get
around logic inversion of time and dur type variables in many cases.

Interesting discussion; once more it's more complicated then I realised at
first.

Yours,
Kas.
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