[PD] haversine formula in Pd

[Alexandre Torres Porres]

some people were saying expr does internal double precision calculation, is
it true? i dont think so...

2015-06-07 3:10 GMT-03:00 Cyrille Henry <ch at chnry.net>:

>
>
> Le 07/06/2015 04:48, Max a écrit :
>
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>> Merci Cyrille,
>>
>> in the formula the intermediate steps are quite small fractions and it
>> seems their precision is important.
>> In the test case the Pd implementation is 8917.74 km off the proper
>> result (2887.26). However I need a precision of about 1m.
>>
> i don't know how you get the 2887.26 km proper result : it's not the value
> computed by the website you send (using value in the patch).
>
>
>> So I assume the haversine formula is not implementable in Pd at all?
>> (unless double precision will be there that is)
>>
>> Or is there a workaround?
>>
>
> i'll thing about it.
> cheers
>
> c
>
>
>
>> m.
>>
>>
>> On 2015년 06월 07일 05:05, Cyrille Henry wrote:
>>
>>> hello,
>>>
>>> pow 2 did not like negative number. use "t f f" and "*" in order to
>>> compute the square of a number.
>>>
>>> i correct 2 of your formula according to what i found in your
>>> link. they both gives the same result : 11805 the same value
>>> computed with your 2nd link gives 12210. for other value, it also
>>> look close. so i guess the difference is number precision.
>>>
>>>
>>> cheers c
>>>
>>>
>>>
>>> Le 06/06/2015 20:18, Max a écrit :
>>>
>>>> I tried to implement the Haversine formula in Pd which should
>>>> give you the distance in km between two lat long coordinates.
>>>>
>>>> https://en.wikipedia.org/wiki/Haversine_formula
>>>> http://www.movable-type.co.uk/scripts/latlong.html
>>>>
>>>> One huge obstacle is the imprecision of the 32bit floats, but
>>>> even without that I can't get the formula to work. I kept 3
>>>> failed implementations in the test-case.
>>>>
>>>> http://rosettacode.org/wiki/Haversine_formula
>>>>
>>>> Could someone give me a hand please?
>>>>
>>>>
>>>>
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>>>>
>>>
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