Re: Could we have elegant version requirement from 5.3 on?

[Ulrich Schmidt <u.sch.zw@...>]

Hi Dirk.

Your test for required modules is possible already.

--8<------------------------------------
  if not package.loaded.bit32 then
    print("QQ...")
    os.exit()
  end
--8<------------------------------------

And yes, you are right, the _VERSION-string could be easier to test.
It should be a array instead a string containing:

--8<------------------------------------
  _VERSION = {
    copyright = "Lua-5.3 #some more text if wanted."
                -- "5.3" can easily extracted. its between first "-"
                -- and first space.
    api_version = 53     -- int: version * 10
    jit_version = 50     -- int: if luajit is running, else: nil
    -- more fields if necessary ...
  }
--8<------------------------------------

Ulrich Schmidt.

Am 26.03.2014 07:46, schrieb Dirk Laurie:
> There seems to be no way of making Lua code say politely:
> "This program requires Lua 5.3" when running under Lua 5.2.
> Instead, one gets a nasty message like
>
> ./myprog.lua:28: unexpected symbol near '&'
>
> as soon as it hits a bitwise operator.
>
> But maybe it is not late for next time round.  We are already
> ignoring one leading `#` line. We could equally well ignore
> all leading `#` lines and tag some of them as expressions to be
> asserted _before_ proceeding to lexical analysis of the file.
> This would allow elegant version control and more.
>
> E.g.
>
> #! /usr/bin/env lua
> #@ _VERSION >= 6.0
> #@ bit32
>
> When Lua 5.3 runs this program, or Lua 6.0 runs it without
> having preloaded a bit32 library, the rest of the file would not
> even be looked at.