bf.vim

function! BF(fxxk) abort
  let mem = 0z00
  for i in range(15)
    let mem = mem + mem
  endfor
  let ip = 0
  let dp = 0
  let out = []
  while ip < len(a:fxxk)
    let c = a:fxxk[ip]
    if c == ">"
      let dp += 1
    elseif c == "<"
      let dp -= 1
    elseif c == "+"
      let mem[dp] = mem[dp] + 1
    elseif c == "-"
      let mem[dp] = mem[dp] - 1
    elseif c == "."
      call add(out, mem[dp])
    elseif c == ","
      let mem[dp] = getchar()
    elseif c == "["
      if mem[dp] == 0
        let s = 0
        while v:true
          let ip += 1
          let c = a:fxxk[ip]
          if c == "["
            let s += 1
          elseif c == "]"
            if s == 0
              break
            else
              let s -= 1
            endif
          endif
        endwhile
      endif
    elseif c == "]"
      if mem[dp] != 0
        let s = 0
        while v:true
          let ip -= 1
          let c = a:fxxk[ip]
          if c == "]"
            let s += 1
          elseif c == "["
            if s == 0
              break
            else
              let s -= 1
            endif
          endif
        endwhile
      endif
    endif
    let ip += 1
  endwhile
  return join(map(out, "nr2char(v:val)"), "")
endfunction

echo BF(">+++++++++[<++++++++>-]<.>+++++++[<++++>-]<+.+++++++..+++.[-]>++++++++[<++ ++>-]<.>+++++++++++[<+++++>-]<.>++++++++[<+++>-]<.+++.------.--------.[-]> ++++++++[<++++>-]<+.[-]++++++++++.")