From Newsgroup: comp.lang.lisp

B. Pym wrote:

Jochen wrote:

This ...

CL-USER 1 > (loop for i for j in '(a b c) collect (cons i j))

((0 . A) (1 . B) (2 . C))

works perfectly on LispWorks, but not with SBCL

FOR is an unknown keyword in FOR or AS clause in LOOP.

I found a way around it 'for i from 0' but am not sure if there is another smarter way to achieve this.

I think the canonical way would be

(loop for i upfrom 0
for j in '(a b c)
collect (cons i j))

newLISP

(map (curry list $idx) '(a b c))

((0 a) (1 b) (2 c))

Gauche Scheme

(let ((i (makeigen)) (col (makelbag)))
(dolist (j '(a b c)) (col (cons (i) j)))
(col))

((0 . a) (1 . b) (2 . c))

Given:

;; Make an integer generator.
(define (makeigen :optional (start 0) (step #f) (m #f))
(let ((i start)
(s step)
(m m)) ;; mod
(if m
(lambda () (begin0 (mod i m) (inc! i s)))
(if s
(lambda () (begin0 i (inc! i s)))
(lambda () (begin0 i (inc! i)))))))

(define (makelbag :optional (raw #f) (pass-through #t))
(let ((bag '()))
(lambda args
(if (null? args)
(if raw bag (reverse bag))
(if pass-through
(begin0 (car args) (push! bag (car args)))
(push! bag (car args)))))))
--
[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

Jochen wrote:

This ...

CL-USER 1 > (loop for i for j in '(a b c) collect (cons i j))

((0 . A) (1 . B) (2 . C))

works perfectly on LispWorks, but not with SBCL

FOR is an unknown keyword in FOR or AS clause in LOOP.

I found a way around it 'for i from 0' but am not sure if there is
another smarter way to achieve this.

I think the canonical way would be

(loop for i upfrom 0
for j in '(a b c)
collect (cons i j))

When variables iterate independently, they can be joined by
rCy:andrCO or rCyandrCO in place of the subsequent rCyforrCO.

For example, (colons added for emphasis):

(loop
:for i :upfrom 0 :and j :in '(a b c)
:collect (cons i j))

((0 . A) (1 . B) (2 . C))

Both control when the loop ends, so the first iterating
expression can be the constraint on when to stop...

(loop
for i below 2 :and j in '(a b c)
collect (cons i j))

((0 . A) (1 . B))

...or the second iterating expression can be the constraint
on when to stop:

(loop
for i below 1000 :and j in '(a b c)
collect (cons i j))

((0 . A) (1 . B) (2 . C))

(loop
for i downfrom 9 :and j in '(a b c)
collect (cons i j))

((9 . A) (8 . B) (7 . C))

See http://www.ai.mit.edu/projects/iiip/doc/CommonLISP/HyperSpec/Body/sec_6-1-2-1.html

"If multiple iteration clauses are used to control
iteration, variable initialization and stepping[1] occur
sequentially by default. The AND construct can be used to
connect two or more iteration clauses when sequential
binding and stepping[1] are not necessary. The iteration
behavior of clauses joined by AND is analogous to the
behavior of the macro DO with respect to DO*."
--
The lyf so short, the craft so long to lerne.
- Geoffrey Chaucer, The Parliament of Birds.
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.lisp

B. Pym wrote:

Jochen wrote:

This ...

CL-USER 1 > (loop for i for j in '(a b c) collect (cons i j))

((0 . A) (1 . B) (2 . C))

works perfectly on LispWorks, but not with SBCL

FOR is an unknown keyword in FOR or AS clause in LOOP.

I found a way around it 'for i from 0' but am not sure if there is another smarter way to achieve this.

I think the canonical way would be

(loop for i upfrom 0
for j in '(a b c)
collect (cons i j))

Gauche Scheme

"!" is somewhat like "do" except that it is optimized
for brevity. So this is shorter than the "loop" solution.

(! (r cons (cons i j)
i 0 +
j :in '(a b c))
(not j) @)

((0 . a) (1 . b) (2 . c))

Given:

(define-syntax !-aux
(syntax-rules (<> @ + - cons cdr :in :across :if ! )
[(_ (:if bool z ...) ((v i u) seen ...) stuff ...)
(!-aux (z ...)
((v i (if bool u v)) seen ...) stuff ...) ]
[(_ (x :in lst z ...) seen (lets ...) stuff ...)
(!-aux (x (and (pair? xs)(pop! xs)) <> z ...)
seen
(lets ... (xs lst)) stuff ...) ]
[(_ (x :across vec z ...) seen (lets ...) stuff ...)
(!-aux (x (and (< i (vector-length v))
(begin0 (vector-ref v i) (inc! i))) <>
z ...)
seen (lets ... (v vec) (i 0)) stuff ...) ]
[(_ (a b <> z ...) (seen ...) stuff ...)
(!-aux (z ...) (seen ... (a b b)) stuff ...) ]
[(_ (a b + z ...) (seen ...) stuff ...)
(!-aux (z ...) (seen ... (a b (+ 1 a))) stuff ...) ]
[(_ (a + n z ...) (seen ...) stuff ...)
(!-aux (z ...) (seen ... (a 0 (+ n a))) stuff ...) ]
[(_ (a b - z ...) (seen ...) stuff ...)
(!-aux (z ...) (seen ... (a b (- a 1))) stuff ...) ]
[(_ (a cons b z ...) (seen ...) stuff ...)
(!-aux (z ...) (seen ... (a '() (cons b a))) stuff ...) ]
[(_ (a b cdr z ...) (seen ...) stuff ...)
(!-aux (z ...) (seen ... (a b (cdr a))) stuff ...) ]
[(_ (a b c z ...) (seen ...) stuff ...)
(!-aux (z ...) (seen ... (a b c)) stuff ...) ]
[(_ (a b) (seen ...) stuff ...)
(!-aux () (seen ... (a b)) stuff ...) ]
[(_ (a) (seen ...) stuff ...)
(!-aux () (seen ... (a '())) stuff ...) ]
;;
[(_ () seen lets a b c ! action ...)
(!-aux () seen lets (a b c) #t (action ...)) ]
[(_ () seen lets a b ! action ...)
(!-aux () seen lets (a b) #t (action ...)) ]
[(_ () seen lets a ! action ...)
(!-aux () seen lets a #t (action ...)) ]
;;
[(_ () ((a b c) z ...) lets bool)
(!-aux () ((a b c) z ...) lets bool a) ]
[(_ () ((a b c) z ...) lets bool @)
(!-aux () ((a b c) z ...) lets bool (reverse a)) ]
[(_ () seen lets bool @ result stuff ...)
(!-aux () seen lets bool (reverse result) stuff ...) ]
[(_ () seen lets bool (what @ x z ...) stuff ...)
(!-aux () seen lets bool (what (reverse x) z ...) stuff ...) ]
[(_ () seen lets bool (what x ... @ z) stuff ...)
(!-aux () seen lets bool (what x ... (reverse z)) stuff ...) ]
[(_ () ((a b c) z ...) lets 0 stuff ...)
(!-aux () ((a b c) z ...) lets (= 0 a) stuff ...) ]
[(_ () seen lets bool result stuff ...)
(let lets (do seen (bool result) stuff ...)) ]
))
(define-syntax !
(syntax-rules ()
[(_ specs bool stuff ...)
(!-aux specs () () bool stuff ...) ]
))
--
[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