Brainfuck compiler to lua, also because why not.

bfc.lua

preamble = [=[
local p, d = 1, {}
function g() return d[p] or 0 end
function s(v) d[p] = v end
function o() io.write(string.char(g())) end
function i() s(string.byte(io.read(1))) end
]=]

subst = {
  ['>'] = "p=p+1\n",
  ['<'] = "p=p-1\n",
  ['+'] = "s(g()+1)\n",
  ['-'] = "s(g()-1)\n",
  ['.'] = "o()\n",
  [','] = "i()\n",
  ['['] = "while g() ~= 0 do\n",
  [']'] = "end\n",
}

function compile(s)
  return preamble .. io.open(s):read('*a'):gsub("[^%+%-<>%.,%[%]]+",""):gsub(".", subst)
end

function run(s)
  assert(loadstring(compile(s), s))()
end

if (...) == '--run' then
  run(select(2,...))
else
  io.write(compile(...))
end