Brainfuck

Brainfuck is an esoteric Turing-complete programming language that is comprised of only 8 instructions.

Instructions

Brainfuck is read token by token, left to right. It utilizes an array of data and an input stream.

Data bytes are assumed to store any value between 0 and 255 inclusive. Some implementations use wrapping (255 + 1 = 0, 0 - 1 = 255), while others do not (255 + 1 = 256, 0 - 1 = -1).

Token	Effect
`>`	Increment the data pointer
`<`	Decrement the data pointer
`+`	Increment the byte at the data pointer
`-`	Decrement the byte at the data pointer
`.`	Output the byte at the data pointer
`,`	Accept one byte of input and store at data pointer
`[`	If byte at data pointer is zero, jump to command after matching `]`
`]`	If byte at data pointer is not zero, jump to command after matching `[`

Examples

Addition

A simple program that adds 2 + 2 could be written like so:

++>++[<+>-]

In brainfuck, as the interpreter/compiler will ignore any characters that are not the ones found above, we can add comments, notes, and newlines for clarity. So the example can be rewritten:

Registers:

First addend/Sum
Second addend

++  // Set the value of the first addend to 2
>++ // Set the value of the second addend to 2
[   // While the second addend is not zero
  <+  // Increment the sum
  >-  // Decrement the second addend
]   // If the second addend isn't zero; continue

The process can be visualized like when using paper computers, with multiple registers that are being incremented and decremented.

Multiplication

This program will multiply two numbers (between 1 and 3) together and print out the result.

+++>+++[-<[->>+>+<<<]>>>[-<<<+>>>]<<]
>++++++++++++++++++++++++++++++++++++++++++++++++.

Expanded, it looks like this:

Registers:

Multiplicand // First num
Multiplier   // Second num
Product
Temp         // Used for refilling multiplier

+++  // set multiplicand
>+++ // set multiplier
[    // while multiplier is not zero
    -   // decrement multiplier
    <   // add multiplicand to product
    [   // while multiplicand is not zero
        -   // decrement multiplicand
        >>+ // increment product
        >+  // increment temp
        <<<
    ]       // if multiplicand is not zero; continue
    >>> // add temp back to multiplicand
    [   // while temp is not zero
        -    // decrement temp
        <<<+ // increment multiplicand
        >>>
    ]        // if temp is not zero; continue
    <<
]
>    // add 0x30 to product for printing
++++++++++++++++
++++++++++++++++
++++++++++++++++
.

Fibonacci[10]

This program will print the ASCII character found at each fibonacci number (0x01, 0x01, 0x02, 0x03, 0x05, etc.)

+[.[->+>+<<]>]

Expanded:

+          // set 0th fib number to 1
[          // while next fib number is not 0
    .      // print current fib number
    [      // while previous fub number is not 0
        -  // decrement previous fib number
        >  // increment next fib number
        +  
        >  // increment 2nd next fix number
        +
        << // go back to previous fib number
    ]      // (if previous fib number is zero,)
    >      // set current fib number to next fib number
]

References

Last modified: 202401040446