From Newsgroup: comp.lang.lisp

(loop for x in '(12 31 2 33)
when (> x 20) collect (expt x 2))

(filter-map~ x (and (> x 20) (* x x)) '(12 31 2 33))


(961 1089)

Given:

(define-syntax filter-map~
(syntax-rules ()
[(_ (v0 v1 ...) expr seq0 seq1 ...)
(filter-map (lambda(v0 v1 ...) expr) seq0 seq1 ...) ]
[(_ v expr seq)
(filter-map (lambda(v) expr) seq) ] ))
--
[T]he problem is that lispniks are as cultish as any other devout group and basically fall down frothing at the mouth if they see [heterodoxy].
--- Kenny Tilton
The good news is, it's not Lisp that sucks, but Common Lisp. --- Paul Graham --- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.lisp

B. Pym wrote:

(loop for x in '(12 31 2 33)
when (> x 20) collect (expt x 2))

(filter-map~ x (and (> x 20) (* x x)) '(12 31 2 33))

(961 1089)

Given:

(define-syntax filter-map~
(syntax-rules ()
[(_ (v0 v1 ...) expr seq0 seq1 ...)
(filter-map (lambda(v0 v1 ...) expr) seq0 seq1 ...) ]
[(_ v expr seq)
(filter-map (lambda(v) expr) seq) ] ))

(keep x (> x 20) (* x x) '(12 31 2 33))

Given:

(define-syntax keep
(syntax-rules ()
[(_ v bool expr seq)
(append-map (lambda(v) (if bool (list expr) '())) seq) ]
[(_ v bool seq)
(filter (lambda(v) bool) seq) ]
[(_ pred seq) (filter pred seq) ]))
--
[T]he problem is that lispniks are as cultish as any other devout group and basically fall down frothing at the mouth if they see [heterodoxy].
--- Kenny Tilton
The good news is, it's not Lisp that sucks, but Common Lisp. --- Paul Graham --- Synchronet 3.21a-Linux NewsLink 1.2