Why does this not work? I had to interrupt it because it just froze doing
nothing.
cf =: 3 : 0
r=.%:y
a=.<.1r2+r
while. ({.a)~:2*{:a do. a=.a,<.1r2+{:r ] r=.r,1%({:r)-{:a end.
]a
)
cf 2
|attention interrupt: cf
| cf 2
On 18 Oct 2011, at 17:23, Raul Miller wrote:
> The best I can think of at the moment is using x: on the floating
> point value for an initial value and then newton's method to gain the
> extra precision you want.
>
> --
> Raul
>
> On Tue, Oct 18, 2011 at 12:09 PM, David Vaughan
> <[email protected]> wrote:
>> I'm hoping to write a verb to compute the continued fraction expansion of a
>> square root. I've done it in Java though there are accuracy issues with
>> floating points and speed issues with using exact numbers (you end up
>> multiplying massive numbers in some cases). Is J equipped to deal with these
>> problems or should I be looking for an alternative method entirely?
>>
>> On 18 Oct 2011, at 16:50, Raul Miller wrote:
>>
>>> On Tue, Oct 18, 2011 at 11:30 AM, David Vaughan
>>> <[email protected]> wrote:
>>>> Can J represent surds exactly instead of reverting to floating point? It
>>>> would be more convenient if I could do that rather than storing the
>>>> squared version.
>>>
>>> Yes, but by generating a verb which would generate the floating point
>>> value and not as a number.
>>>
>>> cubeRootOf5=: %:&5 bind 3
>>>
>>> Of course you can manipulate the resulting numbers but those results
>>> are still floating point:
>>>
>>> (cubeRootOf5 ^ 3:) ''
>>> 5
>>> 5-(cubeRootOf5 ^ 3:) ''
>>> 8.88178e_16
>>>
>>> That said, in some cases, J can clean up floating point discrepancies
>>>
>>> 5-x:(cubeRootOf5 ^ 3:) ''
>>> 0
>>>
>>> but that's from direct manipulation of the values and does not care
>>> about delayed evaluation:
>>>
>>> 5-x:((3 %:5) ^ 3:) ''
>>> 0
>>>
>>> Anyways, J implements the data structures to support symbolic
>>> manipulation but it does not have a particularly large library of
>>> prebuilt symbolic manipulation routines.
>>>
>>> FYI,
>>>
>>> --
>>> Raul
>>> ----------------------------------------------------------------------
>>> For information about J forums see http://www.jsoftware.com/forums.htm
>>
>> ----------------------------------------------------------------------
>> For information about J forums see http://www.jsoftware.com/forums.htm
>>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
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