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- Subject: Re: Closure of lexical environment in Scheme closures
- From: "Aaron Brown" <aaron-lua@...>
- Date: Thu, 11 Nov 2004 15:54:36 -0500
I posted a Scheme program and an equivalent Lua program
earlier. Here are improved versions. (As I said, I'm not
fluent in Scheme, so they might not be exactly equivalent,
but they're close enough for our purposes.)
;; Scheme version:
(define func nil)
(let ((foo 'bar))
(set! func (lambda ()
(set! foo 'baz)) ;; Alters the foo within func.
;; Outside the 'let':
(define foo 'quux) ;; If this were a 'set!', we'd get an
(func) ;; Returns baz.
-- Lua version:
local foo = "bar"
end -- func
foo = "baz" -- Alters the foo within func.
-- Outside the 'do' block:
foo = "quux" -- This is global, but even if it had 'local'
-- in front of it, the 'foo' inside 'func' is still
print(func()) -- Prints "baz"
Remember that every Lua program is one 'chunk' -- that is,
it's surrounded by an implicit 'do' block, kind of like
being in a giant 'let'. (Or 'let*' or 'letrec' or