Friday, 15 February 2013

Erlang and the ancient " 3, 4, 5, [6]" rule

Finally got round to starting to learn  Erlang.
So far all good and great for my head... possibly even my "coding".
Actually its a Neat language. Well worth learning if only for the conceptual journey.

So I was doing a "just above beginner" type exercise and playing around and having lots of
 AH HA / OH NO moments (as ya do).
When I realised that another "Rule" that has been incredibly useful to me for more than 30 years can safely be extended .

The ancient (seriously like pre pyramid ancient) 3:4:5 triangle rule can run one more increment. ( to um 6 ).
For a more fullsome grok.

That is
a triangle of any nominal units (say cubits or rake handles or even meters :) when layed out with:

 side A @ 3 Units
 side B @ 4 Units
 side C at 5 Units

 Will give you a perfect 90 degree (and thereby 2 X 45 degree) corner(s).

This is really useful when laying out large objects or building sites or for basic surveying contour mapping, cutting large sheets ... etc.
I have used it many times indoors and out.

Those same numbers give sane ratios of measurement but reducing the 4 to 2 .
(um later maybe !)
simply put :
Try to design large things so the dimension divide by 2 and or 3.
[ no,  just try it, you'll see when you try to buy materials :]

The next step is that that same triangle will have an area of 6 Units. 

Man how did I miss that ! (DOH)

So now its the 3,4,5,6 rule for me :)

The *ping* moment happened when I was contemplating  "guarding" a function that just happened to be about the area of a triangle and had another clause about circles.
(with some earth building mentally back-grounding I expect)

The human brain (or what I pass off as one) is great at associating random stuff into places it has no business being, (in engineering terms).

Oh and, of course,  there is also the 5,4,3 rule ... sheeze shouda known !
(for Ethernet Networking)
5 4 3 (2 1) rule

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