Grasshopper

algorithmic modeling for Rhino

I don't get this,...

Thx for any enlightenment 

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This example you post highlights and interesting conundrum.

The fact is that the answer you get in U only exists in List B as the list A version has been ignored for the answer.

In order for List Index to work it can only compare the actual entity not the value represented. Think of it like this I have a twin, right down to the very last detail we are identical except for a few strands of DNA.

We stand in two different bus queues. I am in the #1 bus queue and my twin is in the #2 bus queue. The bus inspector is asked to identify the person who is standing in both queues. He looks at the #1 bus queue and then the #2 bus queue and when he reaches my twin he says "That's him! That's the fella right there"

Now that we have identified the twin as the same person, an independent scientist is asked to verify the Bus inspector's answer, so the scientist draws blood from the Twin and does a very complicated DNA analysis to compare with the other bus queue but this time he says that the Twin is not standing in the #1 bus queue only in the #2 bus queue.

Does this help?

The component you should use is called [Find Similar Member]

Great :)

Yes, got it. Learned something fundamental. thx

I feel particularly pedantic today, so let's sharpen up this analogy. Twins either have very different DNA (because each one grew from a different egg and a different sperm), or identical DNA because the egg broke up after fertilisation and grew into two foetuses. Now of course over time DNA defects are introduced during mitosis and just wear over time, but these differences are per cell, not per individual.

If you need to tell monozygotic twins apart, you're better off looking at characteristics acquired during their lifetime such as tattoos, scars, and -most scientifically accurate- immune system particulars. Antibodies for specific infections are only found in those bodies who have been infected or vaccinated, so unless both twins have had exactly the same medical history, you can tell them apart by looking for specific antibody spectra.

In this particular case though I feel an analogy isn't necessary at all. The computer can store data in its memory. For example it can store the number 5. However it can store the number 5 many times, in different memory locations. [Find Similar Member] looks and compares values (i.e. is this number over here equal to that number of over there?). [Item Index] on the other hand only looks at memory addresses. It doesn't care whether two pieces of data are equal, it only cares whether they use the same memory.

--

David

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