Sure, you'll need to handle special cases yourself. But perhaps you don't have t...

Sure, you'll need to handle special cases yourself. But perhaps you don't have to handle all the cases yourself?

As I understand it, one of the new things in IEEE 754 is the idea of a "context", which stores this information. This can be global, but does not need to be. With Python's decimal module it is a thread-local variable.

If you are concerned about, say, mixing thread-local and async, you can also use context methods directly, like:

  >>> import decimal
  >>> x = decimal.Decimal("54.1234")
  >>> y = decimal.Decimal("987.340")
  >>> x+y
  Decimal('1041.4634')
  >>> decimal.getcontext()
  Context(prec=28, rounding=ROUND_HALF_EVEN, Emin=-999999, Emax=999999,
  capitals=1, clamp=0, flags=[], traps=[InvalidOperation, DivisionByZero,
  Overflow])
  >>>
  >>> c1 = decimal.Context(prec=4)
  >>> c1.add(x, y)
  Decimal('1041')
  >>> c2 = decimal.Context(prec=5)
  >>> c2.add(x, y)
  Decimal('1041.5')
  >>> c3 = decimal.Context(prec=5, rounding=decimal.ROUND_DOWN)
  >>> c3.add(x, y)
  Decimal('1041.4')

I don't know what the C or C++ API proposals are.