Re: CL vs scheme macros, namespaces.

On 2024-07-03, B. Pym <No_spamming@noWhere_7073.org> wrote:

The helper macro isn't needed.
>
Scheme (Gauche and Racket):
>
The goal is a let-macro that doesn't need parentheses
around the bindings.  Only one expression is allowed
after the bindings.
>
(define-syntax -->
  (syntax-rules ()
    [ (_  ((k v) ...) expr)
      (let ((k v) ...) expr) ]
    [ (_  ((k v) ...) a b  . more)
      (--> ((k v) ... (a b))  . more) ]
    [ (_  a b c more ...)
      (--> () a b c more ...) ]))

That's stupid; just make it so the wrapping is not allowed,
rather than optional:

(defmacro flat (. bindings-and-expr)
  (tree-case bindings-and-expr
     ((expr) expr)
     ((k v . rest) ^(let ((,k ,v)) (flat ,*rest)))
     (x (error "flat: bad syntax"))))

2> (flat 3)
3
3> (flat x 1 x)
1
4> (flat x 1 y 2 (+ x y))
3
5> (flat x 1 y 2 4 (+ x y))
** flat: bad syntax
** during evaluation at expr-1:6 of form (error "flat: bad syntax")
5> (flat x 1)
** flat: bad syntax
** during evaluation at expr-1:6 of form (error "flat: bad syntax")
5> (flat)
** flat: bad syntax
** during evaluation at expr-1:6 of form (error "flat: bad syntax")

(--> a 2 m 44 z 88 (print (list a m z)))
 ===>
(2 44 88)
>
(--> a 2 m 44 z 88 )
 ===>
; stdin:10:0: -->: bad syntax
;   in: (--> ((a 2) (m 44) (z 88)))

Wut? Your diagnostic is reported against something that the
user didn't write, because it got normalized into
the nested let-style syntax, which is supposd to be
further processed.

What is the point.

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