intersect bug?

[kanen]

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newLISP v.10.7.0 64-bit on Linux IPv4/6 UTF-8 libffi, options: newlisp -h

> (setf a '(4 5 3 6 7))
(4 5 3 6 7)
> (setf b '(3 1 2 0 5))
(3 1 2 0 5)
> (setf c '(4 0 1 2 5))
(4 0 1 2 5)
> (setf d '(0 1 2 0 5))
(0 1 2 0 5)
> (intersect a b c d)
(5 3)

[ralph.ronnquist]

I'll bet you were thinking about that like (or similar to):

Code: Select all

(intersect (intersect a b) (intersect c d))

and not as

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(intersect a b true)

which newlisp did :-)

[ssqq]

intersect
syntax: (intersect list-A list-B)
syntax: (intersect list-A list-B bool)

If you want intersect more list:

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> (set '@lst '((1 2 3 4) (2 3 4 5) (3 4 5 6) (4 5 6 7)))
((1 2 3 4) (2 3 4 5) (3 4 5 6) (4 5 6 7))
> (map (curry apply intersect) (explode @lst 2))
((2 3 4) (4 5 6))
> (apply intersect (map (curry apply intersect) (explode @lst 2)))
(4)



[rickyboy]

If you want intersect more list:

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> (set '@lst '((1 2 3 4) (2 3 4 5) (3 4 5 6) (4 5 6 7)))
((1 2 3 4) (2 3 4 5) (3 4 5 6) (4 5 6 7))
> (map (curry apply intersect) (explode @lst 2))
((2 3 4) (4 5 6))
> (apply intersect (map (curry apply intersect) (explode @lst 2)))
(4)

Or more simply:

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> (set '@lst '((1 2 3 4) (2 3 4 5) (3 4 5 6) (4 5 6 7)))
((1 2 3 4) (2 3 4 5) (3 4 5 6) (4 5 6 7))
> (apply intersect @lst 2)
(4)

With kanen's example:

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> (setf a '(4 5 3 6 7))
(4 5 3 6 7)
> (setf b '(3 1 2 0 5))
(3 1 2 0 5)
> (setf c '(4 0 1 2 5))
(4 0 1 2 5)
> (setf d '(0 1 2 0 5))
(0 1 2 0 5)
> (apply intersect (list a b c d) 2)
(5)

[Lutz]

The intersect function only takes 2 lists, but you could use apply with a reduce 2 parameter to work on more lists:

Code: Select all

> (setf a '(4 5 3 6 7))
(4 5 3 6 7)
> (setf b '(3 1 2 0 5))
(3 1 2 0 5)
> (setf c '(4 0 1 2 5))
(4 0 1 2 5)
> (setf d '(0 1 2 0 5))
(0 1 2 0 5)
>
> (apply intersect (list a b c d) 2)
(5)
> (setf a '(0 5 3 6 7))
(0 5 3 6 7)
> (apply intersect (list a b c d) 2)
(0 5)
> (setf a '(0 5 3 1 7))
(0 5 3 1 7)
> (apply intersect (list a b c d) 2)
(0 5 1)


Older LISPs have a function reduce to do the same. In newLISP that functionality is part of the apply function.

http://www.newlisp.org/downloads/newlis ... #intersect
http://www.newlisp.org/downloads/newlis ... html#apply