## factor-group function

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### factor-group function

To solve a project euler problem i have written this factor-group function:
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`(define (factor-group x)  (letn (fattori (factor x)         unici (unique fattori))    (transpose (list unici (count unici fattori)))))(factor-group 2000);-> ((2 4) (5 3))(factor-group 232792560);-> ((2 4) (3 2) (5 1) (7 1) (11 1) (13 1) (17 1) (19 1))`

Do you known a better/faster way?
Thanks.

cameyo
cameyo

Posts: 91
Joined: Sun Mar 27, 2011 3:07 pm

### Re: factor-group function

Nice.

The factorization is of course the "slow" part, whereas the result juggling is almost irrelevant time-wise. I wouldn't try to improve on your implementation, but as a hind-sight, I probably would have used
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`(map list unici (count unici fattori))`
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`(transpose (list unici (count unici fattori)))`
just because it intuitively would be less structure re-arrangement.
And I also wouldn't have known to use Italian named variables :)
ralph.ronnquist

Posts: 213
Joined: Mon Jun 02, 2014 1:40 am
Location: Melbourne, Australia

### Re: factor-group function

Thanks Ralph.
I am really enjoying newLisp :-)
cameyo
cameyo

Posts: 91
Joined: Sun Mar 27, 2011 3:07 pm

### Re: factor-group function

I forgot to add the inverse function:

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`(setq fg (factor-group 220));-> ((2 2) (5 1) (11 1))`

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`(setq num-fg (apply * (map (lambda (x) (pow (first x) (last x))) fg)));-> 220`

cameyo
cameyo

Posts: 91
Joined: Sun Mar 27, 2011 3:07 pm