Understanding Ethereum Smart Contracts

Post by zodiac » Wed, Nov 29, 2017, 7:55 PM UTC

fokinsean wrote: post #90

coryl wrote: post #62

I've also just begun to play with smart contract programming. One problem I'm having is with event listening. It seems that MetaMask doesn't yet support subscriptions, nor does my localhost testRPC instance pass it in the web3 object. Some have suggested I need to run my own node just to listen for contract events. Has anyone figured out an easier solution?

Quick question, do you have to download the full ethereum chain before you can start messing with smart contracts? Or is there a "light" client you can use?

Post by simonbyrne » Wed, Nov 29, 2017, 8:51 PM UTC

Kranar wrote: post #89

Slartie wrote: post #39

Earlier quoted context omitted.

> There are no floating point numbers. Since you're probably working with "money", this can make things tricky. That is actually a feature when it comes to working with money. You don't ever want to use floating-point arithmetic with monetary values due to its inability to represent all possible decimal fractions of your base unit. This is just as true for over-hyped blockchain stuff as it is for any imaginable appli…

>That is actually a feature when it comes to working with money. You don't ever want to use floating-point arithmetic with monetary values due to its inability to represent all possible decimal fractions of your base unit. This is just as true for over-hyped blockchain stuff as it is for any imaginable application in the "classic" financial sector. I feel like this is constantly repeated but is simply untrue and work…

Post by rthomas6 » Wed, Nov 29, 2017, 9:09 PM UTC

cgh wrote: post #97

scandox wrote: post #10

What I'd greatly appreciate is a walk through of a plausible real world use case. I find it hard to concentrate on the technology itself until I understand the application.

Having recently gone through the prolonged pain of probating a will, I think smart contracts could be used to enforce wills without the need for probate. But of course, that opens up its own can of worms, like the need for potential heirs to maintain a digital identity for possibly decades. What happens if someone cuts all digital ties and effectively becomes a hermit? At least with ordinary probate, you can simply v…

Post by tlrobinson » Wed, Nov 29, 2017, 9:31 PM UTC

joosters wrote: post #92

tlrobinson wrote: post #69

Earlier quoted context omitted.

This seems like a perfect use-case for payment channels, e.x. Lightning Network: Car continuously delivers micropayments to charger while charger continuously delivers power to car, if one stops the other also stops. If the power is cut off prematurely the car only loses maybe a couple cents worth of power. (Payment channels are built using smart contracts, but they’re simple enough that Bitcoin’s more limited smart…

That happens today: when I pump gas into my car, the price on the display goes up. When it hits the limit, the gas flow stops. No blockchain is required.

Post by nicky0 » Wed, Nov 29, 2017, 9:42 PM UTC

barbersturgeon wrote: post #106

Kranar wrote: post #101

Earlier quoted context omitted.

Not every single aspect of HFT is insanely speed critical and even in non-critical areas we still don't use fixed decimal point arithmetic on principle. For example we do a lot of profit/loss reporting and analytics which are not speed critical, we write user interfaces and web apps in Javascript that work with money, so on so forth. I will agree BigDecimal is fine to use if speed really doesn't matter, it's at least…

Honest question - why is that something to avoid? What does the floating point representation buy you that say an int64 doesn't, with the same choice of units ie. 1 = 10^-6 dollars?