unexpected decimal.InvalidOperation

[Skaperen]

when doing decimal.Decimal('-inf')+decimal.Decimal('+inf') i got decimal.InvalidOperation raised. i was expecting to get Decimal('0'). there are a few operations on infinity that normal arithmetic allows such as inf-inf -> 0 and 0*inf -> 0 both of which the decimal.Decimal class does not allow. is there a reason for this or is it just up to whoever implemented decimal.Decimal?