I like fib2 and things were going well but I hit a snag:
]W=:*i.2 2
0 1
1 1
mp=:+/ . *
fib2=:3 : '{. W&mp^:y 0 1'
". }:, (14 5$'(fib2'),"1 (' ',"1 ' ',"1 ":,.>:i.14),"1 '),'
1 1 2 3 5 8 13 21 34 55 89 144 233 377
fib3=: 13 :' ". }:, ((y,5)$'(fib2'),"1 (' ',"1 ' ',"1 ":,.>:i.y),"1 '),''
|domain error: fib2
| {.W&mp ^:y 0 1
It doesn't like the fact that that the fib2 should still be just letters.
It was fun anyway. Linda
-----Original Message-----
From: Programming [mailto:[email protected]] On Behalf
Of Cliff Reiter
Sent: Sunday, February 26, 2017 2:27 PM
To: [email protected]
Subject: Re: [Jprogramming] Explicit fib
Here are a couple approaches:
First, make a list, then take the last thing in it.
fib_list=:3 : 0
z=.0 1
for. i.y-1 do.
z=.z,+/_2{. z
end.
if. y>0 do. z else. 0 end. NB. this only used to make fib_list 0 correct
)
fib_list 10
0 1 1 2 3 5 8 13 21 34 55
fib=:{:@fib_list
fib 10
55
fib 0
0
Or use matrix multiply
mp=:+/ . *
]W=:*i.2 2
0 1
1 1
W takes one fib pair to the next one
W mp 13 21
21 34
fib2=:3 : '{. W&mp^:y 0 1'
fib2 10
55
NB. It even works correctly for negative integers
fib2 _2
_1
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