repl.lua

repl.lua

local function print_if_not_nil(...)
  if ... ~= nil then
    print("-> ", ...)
  end
end

local function try_to_print(line)
  local compiled, errmes = loadstring("return " .. line)
  if compiled then
    print("=> ", compiled())
  else
    print("failed to print. error message was:")
    print(errmes)
  end
end

local maybe_printable

do
  local errs = {
    "'=' expected near '<eof>'",
    "unexpected symbol near"
  }
  
  function maybe_printable(errmes)
    for mes in ipairs(errs) do
      if string.find(errmes, mes, 9, true) then
        return true
      end
    end
    return false
  end
end


while true do
  io.write "> "
  local line = io.read()
  
  if not line then
    break
  elseif line ~= "" then
    local compiled, errmes = loadstring(line)
    
    if compiled then
      print_if_not_nil(compiled())
    elseif maybe_printable(errmes) then
      try_to_print(line)
    else
      print(errmes)
    end
  end
end