Assume, you have additional ' ' (space) at the end of result string.

I have infinity loop for python version on "Sieve of Eratosthenes" test-case.

There is a python input vector :

2>:3g" "-!v\ g30 <

|!`"&":+1_:.:03p>03g+:"&"`|

@ ^ p3" ":<

2 2345678901234567890123456789012345678

It seems, that leading spaces are missing on 2nd and 3rd lines... And probably some spaces on 3rd line
I tested "test" on http://www.bedroomlan.org/tools/befunge-playground#prog=hello,mode=run and there is an infinity loop too.

Seems, this kata is already exist...
http://www.codewars.com/kata/flatten-1

We wrote sorted_insert, length and other functions in previous tasks. Seems, they should be available for usage :)

Yes, you are rigth.
all() function usage is more readable and beautifull.
I will try to use it in such cases.

Thank you!