Re: importing in local scope

[Peter Shook <peter.shook@...>]

> How can I "explode" a table in a local scope like: 
> t = { foo=1, bar=2}
> foo = 2 
> function foobaz()
>   local_explode(t)
>   local baz = foo + bar  -- baz = 3 (not 4)
> end 
> print(foo) -- 2 (not 1)

Here is an approximate solution to your problem.

> t= { foo=1, bar=2}
> foo = 2
> function foobaz() local baz = foo+bar print("baz=",baz) end
> print(foo)
2
> inscope( t, foobaz )
baz=    3
> print(foo)
2

This is the inscope function:

local tagnil = tag(nil)
------------------------------------------------------------------------------
-- make table s the global scope and call function fun with the
remaining
-- arguments.
--
function inscope( s, fun, ... )
  local g  = globals()
  local tm = gettagmethod( %tagnil, 'getglobal' )
  settagmethod( %tagnil, 'getglobal', function( name, value )
      local v
      v = %s[name] if v then return v end -- support delegation via
index
      v = %rawget( %g, name ) if v then return v end 
      -- rawget must be an upvalue
      if %tm then return %tm( name, value ) end
    end )
  globals( s )
  local result = { %call( fun, arg ) }
  %globals( g )
  settagmethod( %tagnil, 'getglobal', tm )
  return unpack(result)
end

Here is another example:

> t = { a=1, b=2, c=3 }
>  a,b = 45,63
> function f(x) print( a+x, b+c ) print(a,b,c) a=99 end
> inscope( t, f, 5 )
6       5
1       2       3
> print(a,b,c)
45      63      nil
> foreach(t,print)
a       99
c       3
b       2

- Peter