Special open dice

I have a question about the dices. In the french game Rêve de Dragon, we need what is called a draconic dice. It is a 8sided-dice that explodes on a 7, but 8 is counted as 0. Is there a way to do that ? Thank you.

I think this would be difficult to achieve without scripts, which require Pro subscription.  You can make a custom dice via rollable table but unfortunately it seems you can't explode rollable tables.  The problem is the 8 counting as 0.  Exploding on a 7 is easy enough. /r 1d8!7

It seems like I have seen a work around for this where the macro was doing 1d8-1.  While that doesn't make the actual 8 on the die a 0, it still results in the same odds of getting a 0, and you still have the range of 0 through 7.  I'm not able to log in and test, but does something like [[[[1d8-1]]!7]] work?

This wouldn't work since if one rolls an 8 then the exploding die would take effect and it wouldn't subtract an additional 1.  Also, this code only sort of works for a single die roll and not a multiple one.  You'd want to do something like /r 4d8!-4   But again, this code doesn't quite work because of the exploding die.

Why wouldn't it work?  The range is 0-7 with 7 being the exploding die, right?  You still have a 1 out of 8 chance of getting 0.  I acknowledge that the 8 displayed on the die will not equal zero, but the mechanical range of the die roll with results of 0 through 7 with 7 exploding should still be satisfied. That is all I am after is satisfying the mechanical needs of the output range.

Sorry.  Maybe I wasn't clear in my initial response.  The problem has nothing to do with labels on the sides of the die.  The problem is two-folds The roll as you have written wouldn't work with multiple dice rolls.  Furthermore, syntactically it won't do what you think it would, namely the dice explosion command can't take evaluated number in the form of [[...]]!7 (EDIT: to further clarify what I mean, [[...]] will evaluate to a particular number so [[1d8-1]]!7 will be equivalent to typing 3!7, if you rolled a 4 for example).  The syntax before ! must be of the form #d#, otherwise it won't trigger (I tested this).  So what you really want to do is /r 1d8!-1 or something like that. The further problem is that once the explosion triggers, it'll no longer be in the range 0-7 but 1-8 as we can't subtract another 1 from the extra die roll.

Yeah, I finally got home to test and it doesn't work with [[]] or () around the initial calculation.  I know I read a thread a while back about doing something similar.  If I manage to track it down, I will post a link.

I was the one who suggests using d8-1 in place of a 0-7 in that previous thread, but IIRC there were no exploding dice there. They do add a complication. However, roll20 does offer a solution. There's an exploding option ( penetrating exploding dice ) which has any exploding dice subtract one. So if its a simple sum, this will work /roll ?{Number Dice|1}d8!p-?{Number Dice} More complicated rolls might not be possible. It depends.

oh cool, i wasn't aware of the "penetrating exploding dice" (what a name haha).

Thank yopu KiKs, it seems to do the job. I'll see on the long term.