On Jan 25, Michael Sperber wrote:
> The fact that the convenient syntax for writing recursive procedures
> is part of `let' is a long-standing wart in the syntax of Scheme.
I disagree.
> It is unintuitive (it expands into `letrec', rather than a simpler
> form of `let), difficult to explain to newcomers to Scheme, and
> disconcerting to the casual reader.
>
> How to fix:
>
> If the syntax needs to be integrated with one of the standard
> binding forms, it should be `letrec', not `let'. However, it would
> be much better to rename named `let' to something else such as
> `rec', `recur' or `recursive'.
If you view
(let ([x v] ...) body ...)
as sugar for
((lambda (x ...) body ...) v ...)
then a named let makes a lot of sense -- it simply gives a name to
that function. It just happens that this needs a letrec in the
expansion, but it's unrelated to the let bindings (now function
bindings) that are still bound in the same way. An unnamed let can
expand to a similar letrec, except that the name is never used so it
can be skipped.
If you're suggesting:
(letrec loop ([x ...]) body ...)
then I don't understand how it can work in any intuitive way. Worse,
I find it very common to write
(define (tree-foo foo tree)
(let loop ([tree tree])
...))
which breaks if it was using a letrec.
--
((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay:
http://www.barzilay.org/ Maze is Life!
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