python filter function

[Michael Burns-Kaurin]

I tried to use the python filter function in glowscript without success.  Is there some trick or does it simply not work?

[Michael Burns-Kaurin]

for this code

b = [0,1,2,3,4,5]

filtered_b = filter(lambda x: x>1, b)

print(list(filtered_b))

I get the error message "Unexpected token name «x», expected punc «,» at line 4: filtered_b = filter(lambda x: x>1, b)"

I use the same code in "regular" python and it works as expected, output is [2, 3, 4, 5].

[Bruce Sherwood]

The problem is that the RapydScript Python-to-JavaScript transpiler does not support this syntax, as can be seen if you run your code at https://sw.kovidgoyal.net/rapydscript/repl/. It appears that the use of "lambda" is not supported. For details, go to

    https://github.com/kovidgoyal/rapydscript-ng

and search for "lambda".

Bruce

[Michael Burns-Kaurin]

I try another method (using a function instead of lambda).  At the rapydscript site, it runs properly.  On glowscript, it does not filter the list and just gives the entire list back.

[Michael Burns-Kaurin]

def criteria(x):

  if x >1:

    return True

  else:

    return False

b = [0,1,2,3,4,5]

filtered_b = filter(criteria, b)

print(list(filtered_b))

[Bruce Sherwood]

Fixed. Thanks for the report.

Bruce

[Michael Burns-Kaurin]

So it should work at glowscript.org?  I must still be missing something.

[Michael Burns-Kaurin]

Tried clearing the cache, still not filtering.

[Bruce Sherwood]

Dumb mistake on my part. Stay tuned.

Bruce

[Bruce Sherwood]

Okay, seems finally to be working properly. Sorry for the confusion. The basic problem is that Python's filter function is rather unusual in having a function name as its first argument, which led to complications in inserting or not inserting async and await in appropriate places in a VPython program.

Bruce

[Michael Burns-Kaurin]

Works!  Thanks!  It must be challenging to replicate python in such an environment.

[Bruce Sherwood]

It is indeed challenging. Obviously RapydScript does the really heavy lifting in converting Python to JavaScript, but the remaining hard part has been appropriately inserting "async" in front of user functions and "await" in front of calls to user functions in order to make it possible for functions to contain statements as pause or waitfor or rate, all of which involve waiting states.

Bruce

[Michael Burns-Kaurin]

Thank you Bruce for doing that work.