“ERROR: Error installing ffi: ERROR: Failed to build gem native extension.”

“An error occurred while installing ffi (1.9.10), and Bundler cannot continue.”

Check your `xcode-select`:

xcode-select -p

In my case, it was:

/Applications/Xcode-beta.app/Contents/Developer

But I had removed Xcode-beta and wanted to use the stable version of Xcode. Make the change:

sudo xcode-select -s /Applications/Xcode.app/Contents/Developer

And now `bundle install` should work. 🎉

Playing music and writing down a few of my picks…

Best:

Lego House  Ed Sheeran

Don’t  Ed Sheeran

Live Like We’re Dying  Kris Allen

Brother  NEEDTOBREATHE

Sugar  Maroon 5

Better:

Hotel California Eagles

Landslide  Fleetwood Mac

God Gave Me You  Dave Barnes

Hall of Fame (feat. will.i.am)  The Script & will.i.am

Stereo Hearts  Gym Class Heroes

Good:

Safe  Phil Wickham

One Thing Remains  Passion

Take It Easy  Eagles

Sweet Home Alabama  Lynyrd Skynyrd

Rocket Man  Elton John

Welcome To New York  Taylor Swift

Payphone  Maroon 5

Code samples are an important part of documentation, especially for one that’s targeted at getting developers to do an integration or build on top of a platform.

‘”If you ask what devs want, it’s more real-world code samples.”

Thinking like a customer is really helpful. Instead of asking: “What’s the use case?” — ask: “Why would a customer use this?”

Direct exposure to customers. A study found that developers given direct exposure to customers of at least 2 hours every 6 weeks produced better UX design.

Support forums. When responding, it’s good to have a QE (Quality Engineer) or developer on-hand. Look at the questions that have been answered on customer forums. Was it answered with a link to the docs?

Imagine having the current time on your Apple Watch, not as “11:24 PM”, but as “352,739” — that is, the current block height.

The Bitcoin block chain height increases by 1 approximately every 10 minutes. Difficulty automatically adjusts so that this always remains roughly true. It’s a Poisson distribution.

From Andrew Poelstra’s paper On Stake and Consensus:

3.4 No Universal Time

Notice that in the previous section we used the number of hash-function calls as our cost function, which is roughly proportional to the number of computations, which in turn is roughly proportional to the amount of heat dissipated, which finally is roughly proportional to the economic and environmental cost of producing these signatures.

An obvious question is whether we can use a cost function which is “cheaper” to satisfy; in particular, why canâ€t we directly use clock time? For that matter, why are we creating chains of DMMS-signed blocks instead of just directly ordering transactions in time, always resolving conflicts in favor of the first?

The answer is that there is no well-defined clock time in a distributed system. Network latency gives a finite speed of information propagation, which we know from special relativity means different observers cannot agree on the time-ordering of events that occur closely in time.

If this were the only problem, requiring transactions to be spaced out by several seconds would be sufficient (if conflicting transactions occur too close together, both are thrown out; but by waiting a few seconds after each transaction all parties can be assured that this wonâ€t happen). However, the situation is worse than this for two reasons:

• “Network latency” is not something that can be bounded in an adversarial setting. An attacker may be able to slow systems by arbitrary amounts using denial-of-service measures, and may be able to physically partition the network by other means.

In relativistic terms, this means that there is no amount of waiting that will assure somebody that they are no longer spacelike separated from other participants in the network.

• Users who are new to the network or have been offline recently need access to historical data. But there is no way to verify after-the-fact what order transactions occurred in, so they cannot be assured that the transactions they are receiving actually occurred before any conflicting ones.

What makes money, money? Where does money come from?

Bitcoin isn’t real money if you think that the definition of real money is government-issued currency. Bitcoin is the only currency that doesn’t appear to be government-issued, backed, or controlled.

Money is used as a medium of exchange, unit of account, and store of value.

There are certain properties that make a thing, whether bitcoins or dollars, good to use as money.

These properties are: portability, durability, divisibility, scarcity, fungibility, and identifiability (non-counterfeitability).

Dollars, which we consider to be real money, work well as money. They are fairly portable: they’re flat, can be folded, and fit in your pocket. They’re not too heavy. They’re durable: they last for a long time. They’re not very divisible, but they are divisible enough. At least they come in specific denominations, so we can easily do math and make change. You can go through the list and consider the suitability of the dollar along all the dimensions listed above.

Then, consider the properties of bitcoin. There are several aspects that many do not understand, two of which are: scarcity and identifiability. Many don’t understand how bitcoin, as a digital commodity, can be scarce. Their intuition betrays them, as they only have other digital items to compare with. Data is normally not scarce, and that is exactly why some people find bitcoin to be interesting. If it functions as intended, then it is a scarce resource, and always will be.

Like dollars, bitcoin is a pure money. It has no use other than as money. This is contrary to commodity-based money, like gold and silver. There’s great value and advantage in building an economy on a pure money.  Humans can design that money to be ideal for its purpose, instead of just taking what’s given to them. Mankind benefits and progresses by inventing new things that make ideas possible. Bitcoin enables many things that were previously impossible, like sending money electronically, and getting bank-account-like capabilities without needing the approval of a third party.

If you want to know what Bitcoin is, you should start with the Bitcoin Whitepaper.

Many years ago, Google made a half-hearted attempt at this with Google Desktop Search. It indexed the files on my computer, but that was about it. Someone should go all the way, and create some kind of local software that records everything I do.

That means it should know everything I’ve typed, everything I’ve read, everything I’ve bookmarked. It should be a smart keylogger, a screen recorder, and take time into account. It should know whether it’s a weekday or a weekend. Whether it’s morning, afternoon, or evening — and behave differently and appropriately. Durations should matter, but not only in that longer events matter more. Something that’s done quickly or as a one-off should also be noted, and possibly even highlighted.

It should have built-in dashboards, reminders, and tips that make it automatically useful, with no manual action required on my part. It should suggest ways for me to be more productive, and show me curated and individualized graphs, charts, and statistics at regular intervals in order to keep me focused on what matters.

Of course, security is of utmost importance. The software needs to prove to me (perhaps with a firewall and/or sandboxing) that none of the data it’s recording ever leaves my computer. Ideally, it would also be open source.

Perhaps this would be a good application of some form of artificial intelligence.