[PD] haversine formula in Pd

[Joel Matthys]

You'll need to do the calculations in an external, where you can use 
double precision.

And..... TADA! Here's the external. I just copied in the C code from the 
Rosettacode link you sent. It gives 2887.26 as the result now.

The external code is here: https://github.com/jwmatthys/haversine-pd

I built the linux version already. It should be easy to build others.

Joel

On 06/06/2015 09:48 PM, Max wrote:
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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.
>
> 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?
>
> 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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