3 ms·

> On a related note, can we agree that an application-programming language today should also include signed-and-unsigned "money-safe" decimal types I’m willing

by samtho 4y ago

> On a related note, can we agree that an application-programming language today should also include signed-and-unsigned "money-safe" decimal types I’m willing to bet that this has to do with how we historically have handled monetary values which is storing and computing it in the respective currency’s fractional unit. The advantage is that you can still do math operations directly on this value (as opposed to an object that contains it) and at most you’ll be off by, in the case of the US dollar, one cent. Because we cannot represent fractional units of the already smallest unit of currency, we have to choose a value anyway to charge or dispense. Unlike, say, if we stored it in dollars as a floating point and we can start compounding errors from the floating point type. What interesting is that pre computers, we didn’t even treat currency values as an real decimal (for base 10 currencies) and the decimal point was simply a convenient way to store partial values. I note this because you don’t see old ledgers where they store more than 2 decimal places, therefore IMO, this was just an integer in disguise all along. Old habits die hard?

hermitdev 4y ago
> Because we cannot represent fractional units of the already smallest unit of currency, we have to choose a value anyway to charge or dispense. Unlike, say, if we stored it in dollars as a floating point and we can start compounding errors from the floating point type. I've spent 20 years mostly working in finance. You'd be surprised at the prevalence of floating points used to represent currency. I cringe every time I see it, but it's surprisingly common (and wrong). More correctly, pricing of securities (from exchanges) is done with integers and a scaling factor. The factor is typically static and doesn't need to be transmitted on every tick. The factor tells you effectively how many fractional digits are present (e.g. the actual price is multiplied by 10^-factor). Factors of 4 or even 6 are somewhat common, but some securities have to go with less precision. I remember in particular Berkshire Hathaway causing issues with overflow using 32-bit ints in the last decade (because they never split their shares, the share price is quite large).
- wruza 4y ago
  You'd be surprised at the prevalence of floating points used to represent currency. I cringe every time We all cringe but then there’s a “floating point or gtfo” ultimatum that most languages present to you. People would be happy to not use FP. But the reality is, you can have a monetary column in a 30 years old database engine, but not in a 5 years old language runtime. When you only have a hammer…
  - DaiPlusPlus 4y ago
    In that situation you’re meant to use integer-cents though.

by samtho 4y ago

hermitdev 4y ago

> Because we cannot represent fractional units of the already smallest unit of currency, we have to choose a value anyway to charge or dispense. Unlike, say, if we stored it in dollars as a floating point and we can start compounding errors from the floating point type. I've spent 20 years mostly working in finance. You'd be surprised at the prevalence of floating points used to represent currency. I cringe every time I see it, but it's surprisingly common (and wrong). More correctly, pricing of securities (from exchanges) is done with integers and a scaling factor. The factor is typically static and doesn't need to be transmitted on every tick. The factor tells you effectively how many fractional digits are present (e.g. the actual price is multiplied by 10^-factor). Factors of 4 or even 6 are somewhat common, but some securities have to go with less precision. I remember in particular Berkshire Hathaway causing issues with overflow using 32-bit ints in the last decade (because they never split their shares, the share price is quite large).

wruza 4y ago
You'd be surprised at the prevalence of floating points used to represent currency. I cringe every time We all cringe but then there’s a “floating point or gtfo” ultimatum that most languages present to you. People would be happy to not use FP. But the reality is, you can have a monetary column in a 30 years old database engine, but not in a 5 years old language runtime. When you only have a hammer…
- DaiPlusPlus 4y ago
  In that situation you’re meant to use integer-cents though.