Financial calculations in Emacs; fundamental questions of information theory
We learn how to compute with compounding interest in Emacs (and discover that the HP-12c is still better.) The two fundamental questions of information theory also get a mention.
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Financial Calculations in Emacs
The HP-12c is the undisputed king of financial calculations involving compound interest. But Emacs can do it too. I wanted to know if it was any ergonomic. The answer is "meh". It would be nice to not have to pick up a separate calculator for compound interest problems, but the HP-12c is so convenient for them that I think I'm going to even though I now know how to do the same thing in Emacs.
Full article (2–6 minute read): Financial Calculations in Emacs
Flashcard of the week
My information theory is weak, but I did read that one book on it. I tried to write flashcards to capture the intuition behind it, and particularly why it was such a big deal.
Which are the two fundamental questions answered by information theory?
This is one of those flashcards. Before information theory, not only did we not have the answers to these two questions – we didn't even know they were questions that could be asked!
The two fundamental questions are
"How many bits are needed to transmit this data?" and "How many bits can be transmitted over this channel?"
Before Shannon, we did have a vague idea that some data are more predictable than others, but we had no idea it was possible to quantify this, nor that the capacity of communication channels could be quantified. Engineers working with radio, telephony, etc. lived on wild experiments and old wisdom passed from one to the next.
This, in some sense, set off a chain reaction that lead to the break-up of AT&T. Before Shannon, they could claim that they had to be a monopoly because that was the only way to ensure signal quality across the entire system. They had to perform integrated testing on the full system when making changes, and they could adapt components to each other to preserve signal quality. After Shannon, it started becoming clear that it's just bits-in-bits-out and it doesn't really matter to signal quality how many operators the bits flow through.
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