bf interpreter written in Lua

main.lua

prog = ">+++++++++[<++++++++>-]<.>+++++++[<++++>-]<+.+++++++..+++.[-]>++++++++[<++++>-]<.>+++++++++++[<+++++>-]<.>++++++++[<+++>-]<.+++.------.--------.[-]>++++++++[<++++>-]<+.[-]++++++++++."
p_ptr = 1

tape = {}
ptr = 0

insts = {
  ['>'] = function() ptr = ptr + 1 end,
  ['<'] = function() ptr = ptr - 1 end,
  ['+'] = function() if tape[ptr] == nil then tape[ptr] = 1 else tape[ptr] = tape[ptr] + 1 end end,
  ['-'] = function() tape[ptr] = tape[ptr] - 1 end,
  ['.'] = function() io.write(string.char(tape[ptr])) end,
  [','] = function() tape[ptr] = io.read() end,
  ['['] = function()
            if tape[ptr] == 0 then
              local cnt = 1
              while true do
                p_ptr = p_ptr + 1
                local c = string.sub(prog, p_ptr, p_ptr)
                if c == '[' then
                  cnt = cnt + 1
                elseif c == ']' then
                  cnt = cnt - 1
                  if cnt == 0 then break end
                end
              end
            end
          end,
  [']'] = function()
            local cnt = 1
            while true do
              p_ptr = p_ptr - 1
              local c = string.sub(prog, p_ptr, p_ptr)
              if c == ']' then
                cnt = cnt + 1
              elseif c == '[' then
                cnt = cnt - 1
                if cnt == 0 then break end
              end
            end
            p_ptr = p_ptr - 1
          end
}

while p_ptr < #prog do
  insts[string.sub(prog, p_ptr, p_ptr)]()
  p_ptr = p_ptr + 1
end