Re: print() and the interactive prompt

[Lorenzo Donati <lorenzodonatibz@...>]

On 14/07/2011 9.06, Peter Odding wrote:
> Patrick Donnelly wrote:
> > Use debug.getinfo to see if your replacement print function is being
> > called from the first function on the call stack (the interpreter).
>
> Luiz Henrique de Figueiredo wrote:
> > lua.c runs lines entered interactively using this:
> > 	status = luaL_loadbuffer(L, line, l, "=stdin");
> >
> > So you can check whether the source is "=stdin":
> > 	print(debug.getinfo(1).source)
>
> Thanks for these suggestions Patrick and Luiz! I'm thinking it may not
> be optimal to call debug.getinfo() every time my redefined print()
> function is called (because it may be called thousands of times even for
> trivial scripts that call print() in a loop) but of course I can just
> not redefine print() when debug.getinfo(1).source ~= '=stdin'.

You could conditionally redefine print, instead of redefining print 
unconditionally and checking every time if source is stdin (untested code):

-- wherever you redefine print write:
print = (function()
  if debug.getinfo(2).source == '=stdin' then
    return prettyprint -- this is your function
  else
    return print -- default print
  end
end)()

alternatively you can define your prettyprint inline

print = (function()
  if debug.getinfo(2).source == '=stdin' then
    return function(...)
     -- prettyprint body
    end
  else
    return print -- default print
  end
end)()




>   - Peter