Make a Brainfuck Interpreter [duplicate]

Question

There already is a Brainfuck interpreter question, but it is from 2011 and not up to date with current site standards and vague in places. I have proposed reposting this in chat, and it was well-received. Here goes.

Objective

Given the Brainfuck code and the program's input as input, run the Brainfuck code. As there are various variants of Brainfuck, here is the one I will use for the challenge:

• There are least 128 cells.
• Cell values are positive integers, having a maximum value of at least 128.
• Going into negative cells in undefined.
• Going into negative numbers is undefined.
• Going above the maximum cell value is undefined.
• Going above the maximum cell is undefined.
• EOF is 0

You may assume that the code will conform to the above constraints and that brackets will be balanced. You may also assume that all input code will be nothing but <>,.+-[].

Testcases

"+[+[<<<+>>>>]+<-<-<<<+<++]<<.<++.<++..+++.<<++.<---.>>.>.+++.------.>-.>>--." -> "Hello, World!"

",[.,]", "abc" -> "abc"

Scoring

As this is code-golf, shortest answer in bytes wins.

Answer 1

simply, 425 bytes

This big boy defines an anonymous function which takes an input string and returns the output of the Brainfuck program.

This anonymous function has to be stored into a variable, and receives the code as the 1st argument ($C), and the input as the 2nd argument ($T).

This is a language being interpreted by JavaScript, which then interprets Brainfuck to generate JavaScript code. 🤯

fn($C$I){if run&empty($I)$I=''$T=&json_decode(<<<J
{".":"O+=String.fromCharCode(T[P]);",",":"T[P]=I[0]?I.shift().charCodeAt(0):0;","<":"P=P?P-1:255;",">":"P=(P+1)%256;","-":"T[P]=T[P]?T[P]-1:255;","+":"T[P]=T[P]?(T[P]+1)%256:1;","[":"while(T[P]){","]":"}"}
J)$N=''each$X in$C if$T[$X]$N=&str_concat($N$T[$X])$F=run$argv->map->constructor('X'run&str_concat("var I=Array.from(X+''),O='',T=[],P=0;"$N"return O"))send run$F($I);}

It is an absolute mess!

Ungolfed - to plain English

Set $fn to the anonymous function($code, $input) {
    If call &empty($input) then {
        Set $input to "".
    }

    Set $tokens to the result of calling &json_decode(<<<JSON
{
    ".": "output += String.fromCharCode(tape[pointer]);",
    ",": "tape[pointer] = input.length ? input.shift().charCodeAt(0) : 0;",
    "<": "pointer = pointer ? pointer - 1 : 255;",
    ">": "pointer = (pointer + 1) % 256;",
    "-": "tape[pointer] = tape[pointer] ? tape[pointer] - 1 : 255;",
    "+": "tape[pointer] = tape[pointer] ? (tape[pointer] + 1) % 256 : 1;",
    "[": "while(tape[pointer]){",
    "]": "}"
}
JSON);
    
    Set $inner_code to "".
    Foreach $char in $code {
        If $tokens[$char] then {
            Set $inner_code to the result of calling &str_concat($inner_code, $tokens[$char], "\n").
        }
    }
    
    Set $js_code to the result of calling &str_concat(
        "input = Array.from(input + '');\nvar output = '';\nvar tape = [];\nvar pointer = 0;\n",
        $inner_code,
        "return output;"
    ).
    
    Set $fn to the result of calling $argv["map"]["constructor"]("input", $js_code).
    
    Return the result of calling $fn($input).
}

Now it is a lot more readable!

---

How does it work?

This will simply read the input code, character by character, and replace the valid tokens into JavaScript code.

Using the array["filter"]["constructor"](code) (but using "map" to save bytes) trick in JSFuck, I can receive a JavaScript function which I can execute normally!

This is FAAAAAAAAAAAAR from the intended way of doing things, but ... it works!

---

Example output

This is the JavaScript code generated for the test cases.

Hello world: +[+[<<<+>>>>]+<-<-<<<+<++]<<.<++.<++..+++.<<++.<---.>>.>.+++.------.>-.>>--.

var fn = function anonymous(X
) {
var I=Array.from(X+''),O='',T=[],P=0;T[P]=T[P]?(T[P]+1)%256:1;while(T[P]){T[P]=T[P]?(T[P]+1)%256:1;while(T[P]){P=P?P-1:255;P=P?P-1:255;P=P?P-1:255;T[P]=T[P]?(T[P]+1)%256:1;P=(P+1)%256;P=(P+1)%256;P=(P+1)%256;P=(P+1)%256;}T[P]=T[P]?(T[P]+1)%256:1;P=P?P-1:255;T[P]=T[P]?T[P]-1:255;P=P?P-1:255;T[P]=T[P]?T[P]-1:255;P=P?P-1:255;P=P?P-1:255;P=P?P-1:255;T[P]=T[P]?(T[P]+1)%256:1;P=P?P-1:255;T[P]=T[P]?(T[P]+1)%256:1;T[P]=T[P]?(T[P]+1)%256:1;}P=P?P-1:255;P=P?P-1:255;O+=String.fromCharCode(T[P]);P=P?P-1:255;T[P]=T[P]?(T[P]+1)%256:1;T[P]=T[P]?(T[P]+1)%256:1;O+=String.fromCharCode(T[P]);P=P?P-1:255;T[P]=T[P]?(T[P]+1)%256:1;T[P]=T[P]?(T[P]+1)%256:1;O+=String.fromCharCode(T[P]);O+=String.fromCharCode(T[P]);T[P]=T[P]?(T[P]+1)%256:1;T[P]=T[P]?(T[P]+1)%256:1;T[P]=T[P]?(T[P]+1)%256:1;O+=String.fromCharCode(T[P]);P=P?P-1:255;P=P?P-1:255;T[P]=T[P]?(T[P]+1)%256:1;T[P]=T[P]?(T[P]+1)%256:1;O+=String.fromCharCode(T[P]);P=P?P-1:255;T[P]=T[P]?T[P]-1:255;T[P]=T[P]?T[P]-1:255;T[P]=T[P]?T[P]-1:255;O+=String.fromCharCode(T[P]);P=(P+1)%256;P=(P+1)%256;O+=String.fromCharCode(T[P]);P=(P+1)%256;O+=String.fromCharCode(T[P]);T[P]=T[P]?(T[P]+1)%256:1;T[P]=T[P]?(T[P]+1)%256:1;T[P]=T[P]?(T[P]+1)%256:1;O+=String.fromCharCode(T[P]);T[P]=T[P]?T[P]-1:255;T[P]=T[P]?T[P]-1:255;T[P]=T[P]?T[P]-1:255;T[P]=T[P]?T[P]-1:255;T[P]=T[P]?T[P]-1:255;T[P]=T[P]?T[P]-1:255;O+=String.fromCharCode(T[P]);P=(P+1)%256;T[P]=T[P]?T[P]-1:255;O+=String.fromCharCode(T[P]);P=(P+1)%256;P=(P+1)%256;T[P]=T[P]?T[P]-1:255;T[P]=T[P]?T[P]-1:255;O+=String.fromCharCode(T[P]);return O
};

console.log(fn());

Cat program: ,[.,]

var fn = function anonymous(X
) {
var I=Array.from(X+''),O='',T=[],P=0;T[P]=I[0]?I.shift().charCodeAt(0):0;while(T[P]){O+=String.fromCharCode(T[P]);T[P]=I[0]?I.shift().charCodeAt(0):0;}return O
};

console.log(fn(prompt("What does the cat say?", "")));

Answer 2

Factor + brainfuck, 13 bytes

run-brainfuck

Try it online!

Try it online! (with input)

Answer 3

Rust + -C overflow-checks=off, 370 bytes

|p:&[u8]|{let(mut o,mut c,mut t,mut k)=(0,0,[0;128],0);loop{match p[o]{62=>c+=1,60=>c-=1,43=>t[c]+=1,45=>t[c]-=1,46=>print!("{}",t[c]as char),44=>t[c]=stdin().bytes().next().unwrap_or(Ok(0)).unwrap(),91=>if t[c]<1{k=1;while k>0{o+=1;if p[o]==91{k+=1};if p[o]==93{k-=1}}},93=>if t[c]>0{k=1;while k>0{o-=1;if p[o]==91{k-=1}if p[o]==93{k+=1}}},_=>()}o+=1}};use std::io::*;

Attempt This Online! (Hello World)

Attempt This Online (Cat)

Will crash when it reaches the end of the program.