Repo containing bits of Brainfuck I've written for fun.
To see if I could implement something real in Brainfuck I implemented the Luhn Algorithm. This takes an ID number such as a credit card number as imput at validates whether or not the number is valid according to the Luhn algorithm outputting "VALID" or "INVALID".
>,[>,]< # READ CARD NUMBER
[ # LOOP OVER INPUT DIGITS BACKWARDS
------------------------------------------------ # CONVERT ASCCI TO DECIMAL
>[>>+<<-]>>>>++<<[->+>-[>+>>]>[+[-<+>]>+>>]<<<<<<]>>[-]>>[-]<<<[<<<+>>>-]>> # DEVIDE N BY 2 TO CALCULATE REMAINDER TO DETERMINE ODD/EVEN
[ # IF N IS ODD ENTER LOOP
<<<<<<[>>>>>>>+>+<<<<<<<<-]>>>>>>>[>>+<<-]>[>+<-]> # DOUBLE CARD DIGIT
>>++++++++++<<[->+>-[>+>>]>[+[-<+>]>+>>]<<<<<<] # DEVIDE DOUBLED VALUE BY 10
>>>>[<<<<<<<<<<<<<+>>>>>>>>>>>>>-]<[<<<<<<<<<<<<+>>>>>>>>>>>>-]<[-]<[-] # ADD TENS AND REMAINDER TOGETHER TO FORM NEW VALUE
<<<<-
]
<<<<<+ # INCREMENT N
<[>>+<<-] # ADD DIGIT VALUE TO SUM
>[<+>-]>[<+>-]<<< # MOVE N & SUM LEFT SINCE WE'VE PROCESSED 1 INPUT DIGIT
] # CONTINUE LOOP UNTIL WE'VE PROCESSED ALL INPUT DIGITS AND WE'RE BACK AT CELL 0 WIN N IN CELL 1 AND SUM IN CELL 2
>>>>++++++++++<<[->+>-[>+>>]>[+[-<+>]>+>>]<<<<<<] # DEVIDE SUM BY 10
>>>[[-]+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.+++++.[-]] # IF THERE WAS A REMAINDER PRINT "IN"
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++. # PRINT "V"
---------------------. # PRINT "A"
+++++++++++. # PRINT "L"
---. # PRINT "I"
-----. # PRINT "D"
>,[>,]<[------------------------------------------------>[>>+<<-]>>>>++<<[->+>-[>+>>]>[+[-<+>]>+>>]<<<<<<]>>[-]>>[-]<<<[<<<+>>>-]>>[<<<<<<[>>>>>>>+>+<<<<<<<<-]>>>>>>>[>>+<<-]>[>+<-]>>>++++++++++<<[->+>-[>+>>]>[+[-<+>]>+>>]<<<<<<]>>>>[<<<<<<<<<<<<<+>>>>>>>>>>>>>-]<[<<<<<<<<<<<<+>>>>>>>>>>>>-]<[-]<[-]<<<<-]<<<<<+<[>>+<<-]>[<+>-]>[<+>-]<<<]>>>>++++++++++<<[->+>-[>+>>]>[+[-<+>]>+>>]<<<<<<]>>>[[-]+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.+++++.[-]]++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.---------------------.+++++++++++.---.-----.
Can test brainfuck with this interpreter here
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