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  • Re: Subject: Re: Detele repeated in a list

    From B. Pym@Nobody447095@here-nor-there.org to comp.lang.lisp,comp.lang.scheme on Sat Aug 9 18:35:36 2025
    From Newsgroup: comp.lang.scheme

    B. Pym wrote:

    Mariano Montone wrote:

    I have this piece of code, that sould delete all the repeated elements from a list :

    (defun apaga-repetidos (lista)
    (let ((p (first lista))
    (r (rest lista)))
    (if (null lista)
    nil
    (if (equal p r)
    (apaga-repetidos r)
    (cons p (apaga-repetidos r))))))


    You are comparing an element with a list when you do (equal p r)

    Try this:

    (defun apaga-repetidos (lista)
    (apaga-repetidos-2 lista (make-hash-table :test #'equal)))

    (defun apaga-repetidos-2 (lista vistos)
    (if (null lista)
    nil
    (let ((p (first lista))
    (r (rest lista)))
    (if (gethash p vistos)
    (apaga-repetidos-2 r vistos)
    (progn
    (setf (gethash p vistos) t)
    (cons p (apaga-repetidos-2 r vistos)))))))

    : (apaga-repetidos '((1 2) (2 2) (3 2) (4 2) (5 2)
    (6 2) (7 2) (8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
    (4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4) ))

    Result: ((1 2) (2 2) (3 2) (4 2) (5 2) (6 2) (7 2) (8 2) (8 3) (8 4)
    (7 4) (6 4) (5 4)
    (4 4) (4 5) (3 5) (3 6) (4 6))


    (define (rem-dups List)
    (do ((res '() (if (member x res) res (cons x res)))
    (x #f))
    ((null? List) res)
    (set! x (pop! List))))


    (rem-dups '((1 2) (2 2) (3 2) (4 2) (5 2)
    (6 2) (7 2) (8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
    (4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4)))
    ===>
    ((4 6) (3 6) (3 5) (4 5) (4 4) (5 4) (6 4) (7 4) (8 4) (8 3) (8 2)
    (7 2) (6 2) (5 2) (4 2) (3 2) (2 2) (1 2))

    Shorter:

    (define (rem-dups List)
    (Do ((r '() (if (member x r) r (cons x r)))
    (x (pop List) <>))
    ((null? List) @ r)))

    (rem-dups '((1 2) (2 2) (3 2) (4 2) (5 2)
    (6 2) (7 2) (8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
    (4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4)))
    ===>
    ((1 2) (2 2) (3 2) (4 2) (5 2) (6 2) (7 2) (8 2) (8 3) (8 4)
    (7 4) (6 4) (5 4) (4 4) (4 5) (3 5) (3 6) (4 6))

    Given:

    (define-syntax pop
    (syntax-rules ()
    [ (_ xs)
    (if (pair? xs)
    (begin0 (car xs) (set! xs (cdr xs)))
    #f) ] ))
    (define-syntax Do-aux
    (syntax-rules (<> @)
    [(_ ((a b <>) d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a b b)) z ...) ]
    [(_ ((a b c) d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a b c)) z ...) ]
    [(_ ((a b) d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a b)) z ...) ]
    [(_ ((a) d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a '())) z ...) ]
    [(_ (a d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a '())) z ...) ]
    [(_ () seen (a b ... @ xs) z ...)
    (Do-aux () seen (a b ... (reverse xs)) z ...) ]
    [(_ () seen till body ...)
    (do seen till body ...) ]))
    (define-syntax Do
    (syntax-rules ()
    [(_ specs till body ...)
    (Do-aux specs () till body ...) ]))
    --
    [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 B. Pym@Nobody447095@here-nor-there.org to comp.lang.lisp,comp.lang.scheme on Sat Aug 9 18:43:57 2025
    From Newsgroup: comp.lang.scheme

    B. Pym wrote:

    B. Pym wrote:

    Mariano Montone wrote:

    I have this piece of code, that sould delete all the repeated elements from a list :

    (defun apaga-repetidos (lista)
    (let ((p (first lista))
    (r (rest lista)))
    (if (null lista)
    nil
    (if (equal p r)
    (apaga-repetidos r)
    (cons p (apaga-repetidos r))))))


    You are comparing an element with a list when you do (equal p r)

    Try this:

    (defun apaga-repetidos (lista)
    (apaga-repetidos-2 lista (make-hash-table :test #'equal)))

    (defun apaga-repetidos-2 (lista vistos)
    (if (null lista)
    nil
    (let ((p (first lista))
    (r (rest lista)))
    (if (gethash p vistos)
    (apaga-repetidos-2 r vistos)
    (progn
    (setf (gethash p vistos) t)
    (cons p (apaga-repetidos-2 r vistos)))))))

    : (apaga-repetidos '((1 2) (2 2) (3 2) (4 2) (5 2)
    (6 2) (7 2) (8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
    (4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4) ))

    Result: ((1 2) (2 2) (3 2) (4 2) (5 2) (6 2) (7 2) (8 2) (8 3) (8 4)
    (7 4) (6 4) (5 4)
    (4 4) (4 5) (3 5) (3 6) (4 6))


    (define (rem-dups List)
    (do ((res '() (if (member x res) res (cons x res)))
    (x #f))
    ((null? List) res)
    (set! x (pop! List))))


    (rem-dups '((1 2) (2 2) (3 2) (4 2) (5 2)
    (6 2) (7 2) (8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
    (4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4)))
    ===>
    ((4 6) (3 6) (3 5) (4 5) (4 4) (5 4) (6 4) (7 4) (8 4) (8 3) (8 2)
    (7 2) (6 2) (5 2) (4 2) (3 2) (2 2) (1 2))

    Shorter:

    (define (rem-dups List)
    (Do ((r '() (if (member x r) r (cons x r)))
    (x (pop List) <>))
    ((null? List) @ r)))

    (rem-dups '((1 2) (2 2) (3 2) (4 2) (5 2)
    (6 2) (7 2) (8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
    (4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4)))
    ===>
    ((1 2) (2 2) (3 2) (4 2) (5 2) (6 2) (7 2) (8 2) (8 3) (8 4)
    (7 4) (6 4) (5 4) (4 4) (4 5) (3 5) (3 6) (4 6))

    Given:

    (define-syntax pop
    (syntax-rules ()
    [ (_ xs)
    (if (pair? xs)
    (begin0 (car xs) (set! xs (cdr xs)))
    #f) ] ))
    (define-syntax Do-aux
    (syntax-rules (<> @)
    [(_ ((a b <>) d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a b b)) z ...) ]
    [(_ ((a b c) d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a b c)) z ...) ]
    [(_ ((a b) d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a b)) z ...) ]
    [(_ ((a) d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a '())) z ...) ]
    [(_ (a d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a '())) z ...) ]
    [(_ () seen (a b ... @ xs) z ...)
    (Do-aux () seen (a b ... (reverse xs)) z ...) ]
    [(_ () seen till body ...)
    (do seen till body ...) ]))
    (define-syntax Do
    (syntax-rules ()
    [(_ specs till body ...)
    (Do-aux specs () till body ...) ]))

    Shorter yet:

    (define (rem-dups List)
    (Do ((r '() (if (member x r) r (cons x r)))
    (x (pop List) <>))
    ((not x) @ r)))
    --
    The good news is, it's not Lisp that sucks, but Common Lisp. --- Paul Graham --- Synchronet 3.21a-Linux NewsLink 1.2
  • From B. Pym@Nobody447095@here-nor-there.org to comp.lang.lisp,comp.lang.scheme on Sat Aug 9 22:46:55 2025
    From Newsgroup: comp.lang.scheme

    B. Pym wrote:

    B. Pym wrote:

    B. Pym wrote:

    Mariano Montone wrote:

    I have this piece of code, that sould delete all the repeated elements
    from a list :

    (defun apaga-repetidos (lista)
    (let ((p (first lista))
    (r (rest lista)))
    (if (null lista)
    nil
    (if (equal p r)
    (apaga-repetidos r)
    (cons p (apaga-repetidos r))))))


    You are comparing an element with a list when you do (equal p r)

    Try this:

    (defun apaga-repetidos (lista)
    (apaga-repetidos-2 lista (make-hash-table :test #'equal)))

    (defun apaga-repetidos-2 (lista vistos)
    (if (null lista)
    nil
    (let ((p (first lista))
    (r (rest lista)))
    (if (gethash p vistos)
    (apaga-repetidos-2 r vistos)
    (progn
    (setf (gethash p vistos) t)
    (cons p (apaga-repetidos-2 r vistos)))))))

    : (apaga-repetidos '((1 2) (2 2) (3 2) (4 2) (5 2)
    (6 2) (7 2) (8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
    (4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4) ))

    Result: ((1 2) (2 2) (3 2) (4 2) (5 2) (6 2) (7 2) (8 2) (8 3) (8 4)
    (7 4) (6 4) (5 4)
    (4 4) (4 5) (3 5) (3 6) (4 6))


    (define (rem-dups List)
    (do ((res '() (if (member x res) res (cons x res)))
    (x #f))
    ((null? List) res)
    (set! x (pop! List))))


    (rem-dups '((1 2) (2 2) (3 2) (4 2) (5 2)
    (6 2) (7 2) (8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
    (4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4)))
    ===>
    ((4 6) (3 6) (3 5) (4 5) (4 4) (5 4) (6 4) (7 4) (8 4) (8 3) (8 2)
    (7 2) (6 2) (5 2) (4 2) (3 2) (2 2) (1 2))

    Shorter:

    (define (rem-dups List)
    (Do ((r '() (if (member x r) r (cons x r)))
    (x (pop List) <>))
    ((null? List) @ r)))

    (rem-dups '((1 2) (2 2) (3 2) (4 2) (5 2)
    (6 2) (7 2) (8 2) (8 3) (8 4) (7 4) (6 4) (5 4) (4 4)
    (4 5) (3 5) (3 6) (4 6) (4 5) (4 4) (5 4)))
    ===>
    ((1 2) (2 2) (3 2) (4 2) (5 2) (6 2) (7 2) (8 2) (8 3) (8 4)
    (7 4) (6 4) (5 4) (4 4) (4 5) (3 5) (3 6) (4 6))

    Given:

    (define-syntax pop
    (syntax-rules ()
    [ (_ xs)
    (if (pair? xs)
    (begin0 (car xs) (set! xs (cdr xs)))
    #f) ] ))
    (define-syntax Do-aux
    (syntax-rules (<> @)
    [(_ ((a b <>) d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a b b)) z ...) ]
    [(_ ((a b c) d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a b c)) z ...) ]
    [(_ ((a b) d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a b)) z ...) ]
    [(_ ((a) d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a '())) z ...) ]
    [(_ (a d ...) (seen ...) z ...)
    (Do-aux (d ...) (seen ... (a '())) z ...) ]
    [(_ () seen (a b ... @ xs) z ...)
    (Do-aux () seen (a b ... (reverse xs)) z ...) ]
    [(_ () seen till body ...)
    (do seen till body ...) ]))
    (define-syntax Do
    (syntax-rules ()
    [(_ specs till body ...)
    (Do-aux specs () till body ...) ]))

    Shorter yet:

    (define (rem-dups List)
    (Do ((r '() (if (member x r) r (cons x r)))
    (x (pop List) <>))
    ((not x) @ r)))

    Shorter yet:

    (define (rem-dups List)
    (Do ((r '() (adjoin x r))
    (x (pop List) <>))
    ((not x) @ r)))

    Given:

    (define (adjoin x xs) (if (member x xs) xs (cons x xs)))
    --
    The good news is, it's not Lisp that sucks, but Common Lisp. --- Paul Graham --- Synchronet 3.21a-Linux NewsLink 1.2