Brainfuck in Monkey Lang

bf.monkey

#!./monkey-lang

let fill = fn(x, i) {
  let xs = []
  while (i > 0) {
    xs = push(xs, x)
    i = i - 1
  }
  return xs
}

let buildJumpMap = fn(program) {
  let lb = []
  let rb = []
  let n = 0
  while (n < len(program)) {
    if (program[n] == "[") {
      lb = push(lb, n)
    }
    if (program[n] == "]") {
      rb = push(rb, n)
    }
    n = n + 1
  }

  let jumps = {}
  let i = 0
  while (i < len(lb)) {
    jumps[lb[i]] = rb[i]
    jumps[rb[i]] = lb[i]
    i = i + 1
  }
  return jumps
}

let printable = " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~"

let ord = fn(s) {
  return printable[s] + 32
}

let read = fn() {
  let buf = input()
  if (len(buf) > 0) {
    return ord(buf[0])
  }
  return 0
}

let chr = fn(x) {
  if (x < 32) {
    return "??"
  }
  if (x > 127) {
    return "??"
  }
  return printable[x - 32]
}

let write = fn(x) {
  print(chr(x))
}

let VM = fn(program) {
  let jumps = buildJumpMap(program)

  let ip = 0
  let dp = 0
  let memory = fill(0, 32)

  while (ip < len(program)) {
    let op = program[ip]

    if (op == ">") {
      dp = dp + 1
    } else if (op == "<") {
      dp = dp - 1
    } else if (op == "+") {
      memory[dp] = memory[dp] + 1
    } else if (op == "-") {
      memory[dp] = memory[dp] - 1
    } else if (op == ".") {
      write(memory[dp])
    } else if (op == ",") {
      memory[dp] = read()
    } else if (op == "[") {
      if (memory[dp] == 0) {
        ip = jumps[ip]
      }
    } else if (op == "]") {
      if (memory[dp] != 0) {
        ip = jumps[ip]
      }
    }
    ip = ip + 1
  }

  print("memory:")
  print(memory)
}

// ???
// let program = "+++++>+++[-<->]<."

// Hello World
// let program = "++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++."

// 2 + 5
let program = "++> +++++ [<+>-] ++++++++ [<++++++>-] < ."

VM(program)