assert() and local vars

["Eric Ries" <eries@...>]

Hello all... I'm working on a wrapper for C-style asserts in Lua. I am
wondering if something like this would work:

function foo(a)
  local b
  b = a * 2
  ... etc
  LuaAssert( "a > b" )
  ... etc
end

function LuaAssert( cmd )
   local result = dostring( cmd )
   if result and result > 0 then
      c-style-assert( 0 )
   end
end

The problem is that the locals a and b are not defined in LuaAssert... is
there some way to get around this?