!aBF'

!aBF' is the language whose name is pronounced "not a brainfuck derivative". The language uses 5 commands which manipulate a sole accumulator. The accumulator initially starts at zero. Additionally, new commands can be appended to the end of the program during execution, making loops possible.

Commands

Command	Name	Description
!	not	Don't do the following command.
a	AAAAAAAAAAAAAAA	Output the accumulator
B	between	Take everything between this B and the second-next B (or the end of the program), and replicate it to the end of the program a number of times equal to the value of the accumulator.
F	five	Add 5 to the accumulator.
'	derivative	Replace the value of the accumulator with its arithmetic derivative.

Examples

Output 420:

FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFa

Truth-machine:

?'BaBB

Replace the ? with F for 1 or remove the ? for 0. As an example of this language's weirdness, the 1 case expands to a non-periodic pattern of a's and B's:

F'BaBBaBBaaBBaaaaBBaaaaaaaaBB...

Truth-machine golfed:

?'BaB

Implementations

• Pyth implementation. Provide the !aBF' program as input. (Note: this implementation is improper, because numbers are not output in caps lock)

K0W<ZlzJ@zZIqJ\!=hZ.?IqJ\aK.?IqJ\B=+z*j\B<c>zhZ\B2K.?IqJ\F=+K5.?IqJ\'=Ksm/KdPK)))))=hZ

• Python Interpretation. Provide program as input.