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I abuse `Decimal` all the time in python. I usually make a little helper with a very short name like def d(in: Any) -> Decimal Then use that everywhere I ex

I abuse `Decimal` all the time in python. I usually make a little helper with a very short name like def d(in: Any) -> Decimal Then use that everywhere I expect a float (or just anywhere). Decimal's constructor is so forgiving allowing strings, ints, floats, other decimals it is so convenient to use. Of course there is the perf penalty but I always think the precision is worth the tradeoff.

caturopath 5y ago
Decimal has the same fundamental representation issues that float does, albeit with greater configuration.
- bsder 5y ago
  It does, but those issues manifest themselves in ways that humans have been trained to operate. "Round to nearest even" for binary floating point is weird to anyone who doesn't have a numerics background. "Round 0.5 up" is normal to humans because that's what most have been taught. Future programming languages should probably default to Decimal Floating Point and allow people to opt-in to binary floating point on request.
  - caturopath 5y ago
    > It does, but those issues manifest themselves in ways that humans have been trained to operate. Not really. If you do computations like "convert Fahrenheit to Celsius" or "pay 6 days of interest at this APR" or a million other things, you run into the same basic faulty assumptions as ever
  - eru 5y ago
    Rounding to even makes sense for human-facing decimals as well. That's what they do in accounting, I think? At least Wikipedia tells me it's also called banker's rounding. Incidentally, it's also what Python's Decimal does by default. See https://docs.python.org/3/library/decimal.html#rounding-modes https://docs.python.org/3/library/decimal.html#rounding-mode...
zokier 5y ago
wouldn't just from decimal import Decimal as d work as well?
- leetrout 5y ago
  Sorry, I am doing stuff in the function... here is one of the old ones from code I can share def dec(value, prec=4): """Return the given value as a decimal rounded to the given precision.""" if value is None: return Decimal(0) value = Decimal(value) ret = Decimal(str(round(value, prec))) if ret.is_zero(): # this avoids stuff like Decimal('0E-8') return Decimal(0) return ret

caturopath 5y ago

Decimal has the same fundamental representation issues that float does, albeit with greater configuration.

bsder 5y ago
It does, but those issues manifest themselves in ways that humans have been trained to operate. "Round to nearest even" for binary floating point is weird to anyone who doesn't have a numerics background. "Round 0.5 up" is normal to humans because that's what most have been taught. Future programming languages should probably default to Decimal Floating Point and allow people to opt-in to binary floating point on request.
- caturopath 5y ago
  > It does, but those issues manifest themselves in ways that humans have been trained to operate. Not really. If you do computations like "convert Fahrenheit to Celsius" or "pay 6 days of interest at this APR" or a million other things, you run into the same basic faulty assumptions as ever
- eru 5y ago
  Rounding to even makes sense for human-facing decimals as well. That's what they do in accounting, I think? At least Wikipedia tells me it's also called banker's rounding. Incidentally, it's also what Python's Decimal does by default. See https://docs.python.org/3/library/decimal.html#rounding-modes https://docs.python.org/3/library/decimal.html#rounding-mode...

zokier 5y ago

wouldn't just from decimal import Decimal as d work as well?

leetrout 5y ago
Sorry, I am doing stuff in the function... here is one of the old ones from code I can share def dec(value, prec=4): """Return the given value as a decimal rounded to the given precision.""" if value is None: return Decimal(0) value = Decimal(value) ret = Decimal(str(round(value, prec))) if ret.is_zero(): # this avoids stuff like Decimal('0E-8') return Decimal(0) return ret