_nix wrote:

Oh, wow. This is really surprising. I'd call it a bug, or an incompatibility, but… I think its potential uses outweigh breaking any hypothetical project which relies on the value of a nonexistant input that shares the name with one of a custom block calling that one to be 0.

Edit: I haven't read far through it yet, but this paper on dynamic scoping (I think it even introduced/formalized the concept?) is interesting: http://galois.com/wp-content/uploads/2014/08/pub_JL_ImplicitParameters.pdf

badatprogrammingibe wrote:

Example:
https://scratch.mit.edu/projects/259998618/
https://beta.scratch.mit.edu/#259998618

• Go through all stack frames in reverse order of insertion (almost like a… stack!)
  
• If this is not a script with a custom block hat, keep traversing (i.e., skip next few steps)
  
• If this custom block has the relevant parameter, immediately report its value
  
• Else, continue traversing
  
• Once we've finished traversing, return 0
  

• (Still) go through all stack frames in reverse order
  
• (Still) If this is not a script with a custom block hat, keep traversing (i.e, skip next few steps)
  
• (Diff) Immediately report either 0 or the value, depending on whether the custom block has the value
  
• (Still) If no custom hats were found, report 0
  

kchadha wrote:

This was answered in a discussion offline:

getParams searches for a params object in the stack. When it encounters a params object, it can check it for the parameter being searched for. After the defaults branch being merged, if its not there that implies the param is not from the current running procedure.
Since the parameter is not in the current procedure we can shortcut out of any more searching.

jokebookservice1 wrote:

My understanding is that dynamic scoping was recently removed, 13 days ago. I can't see this, though, in the latest published previews (e.g. llk.github.io/scratch-gui/develop, llk.github.io/scratch-vm). I'm not sure if the former has pulled in the latest VM changes yet, or if the latter even is updated ever.

imfh wrote:

If you add any parameters to y it outputs 0 though… That is very interesting.

for (let i = this.stackFrames.length - 1; i >= 0; i--) {
    ...
    const frame = this.stackFrames[i];
    if (frame.params === null) {
        continue;
    }
    if (frame.params.hasOwnProperty(paramName)) { ... }
    return null;
}

imfh wrote:

If you add any parameters to y it outputs 0 though… That is very interesting.

_nix wrote:

So I guess the solution here is to remove those three lines I linked – but of course, I wonder why they were put there to begin with.

_nix wrote:

So I guess the solution here is to remove those three lines I linked – but of course, I wonder why they were put there to begin with.

define proc (arg)
broadcast [do something v] and wait

when I receive [do something v]
say (arg ::custom-arg)

CatIsFluffy wrote:

Someone trying to sneak in something useful for ATers?

JGames101 wrote:

Three Days to go until Scratch 3 and it hasn't been removed yet

badatprogrammingibe wrote:

Example:
https://scratch.mit.edu/projects/259998618/
https://beta.scratch.mit.edu/#259998618