Function causes a crash

Hector1945

@Gothon There is no crash anymore, but if I uncomment the second part of the function, the trail doesn't display anymore, while it used to...

Hector1945

@DaddyJDM I get an error for attempting to index non array type

spikey

@Hector1945 wow, the response time is quite fast here 😄 @Gothon +1, @DaddyJDM +1 even go with:

trail[0]=[] //the first time
trail[0][0]={} //the first time
trail[0][0].x=ball.x
trail[0][0].y=ball.y

Hector1945

@spikey Why do I get a "unrecognized type: 4" on the line 79 ?

Gothon

There is actually another caveat. If len(trail) is 1, the loop will become for i = 0 to 0 flipping to positive direction and not iterate. There are a couple ways of avoiding this problem. You can write a while loop or use

for j = 0 to len(trail) loop
    i = len(trail) - 1 - j

Though I notice that your loop uses both trail[i] and trail[i+1], so you probably need to write it as:

for j = 0 to len(trail)-1 loop
    i = len(trail) - 2 - j
    ...
repeat

so that it loops len(trail)-2 through 0 since anything outside that range will give you an out of bounds array index.

Hector1945

So I tried replacing

for i = len(trail)-1 to -1 step -1 loop

with

for i = len(trail)-1 to 0 loop

and starting the game with 2 values already in the array, and the trail works, but I still get the crash...

Gothon

@Hector1945 said in Function causes a crash:

but I still get the crash...

Right the first value of i is len(trail)-1 = 1 and i+1 = 2 which is out of bounds for an array of size 2 (the valid indices are 0, 1). Since you are writing trail[i+1], you need to start the loop with for i = len(trail)-2 ....

PickleCatStars

I had ’unrecognised type’ error before when accessing an array. Martin said to change the iterator Name to something unique (the ’x’ in ’for x = 0 to..’), and that worked. It was a fuze bug, not something I’d done that time...

Hector1945

@Gothon Wouldn't I get an error if it was out of bounds ? Because the crash only occurs like 20 seconds in the game, way after the array gets completely filled with 50 values...

Gothon

@Hector1945 I agree that Fuze should give you an out of bounds error, but when Fuze itself is crashing it is difficult to know what to expect. It can be tricky to trace back to the cause of undefined behaviors.

Hector1945

If I do the len(trail)-2 it does not crash but the trail doesn't display properly

Hector1945

Oh ok it just didn't execute the command because len(trail)-2 = 0 if trail has 2 values

spikey

@Hector1945 Glad you solved it , the unrecognized type 4 error probably went from adding a value to a not properly initialized array (or reading from a such). (Because of wrong dimension, index). Is it technically a 'void' type? What means its just pointing to a place in memory, but its not clear yet, what the bytes mean there: number, string, array. If somebody knows for sure please comment on this. It would be nice to know for sure.

Hector1945

Oh no it isn't solved ! I now have a lead though, because apparently it does come from the trail[0] = [{ball.x,ball.y},moving] because if I replace that line by trail[0] = 5 or any random int, then it doesn't crash ! I just don't know how to solve it, because when I try I get an unrecognised type 4 error.

spikey

Ok, is moving a global variable? To test if this is the problem, add a line before:
moving = false
Which will make sure it is declared implicitly as a boolean and defined as false.

Hector1945

I tried, and it still crashes.

vinicity

What is trail[0] = [{ball.x,ball.y},moving] supposed to accomplish anyway?

It looks like you are assigning an array containing a vector and something else to trail[0]?

And then you treat the result as an int?

Hector1945

No I treat the result as an array of a vector and a boolean. The vector is used to log the 50 most recent positions of the ball, in order to make a trail that follows the exact path of the ball, like in the reference video. The "moving" boolean is used to determine if a trail should actually be drawn to that point. There might be a better way of doing this, but I haven't figured it out.

vinicity

Sorry, I didn’t read the code properly. Now I see how you do it.

Not sure if it would help, but maybe using a struct would be better and then having an array of structs instead?

vinicity

Did you change the loop? Backwards loops in Fuze do not work as one would suspect.

I find it is always better to use a while loop instead and handling the counter yourself in those cases.