Complete Interval Arithmetic and Its Implementation on the Computer

Let IIR be the set of closed and bounded intervals of real numbers. Arithmetic in IIR can be defined via the power set IPIR (the set of all subsets) of real numbers. If in case of division zero is not contained in the divisor arithmetic in IIR is an algebraically closed subset of the arithmetic in IPIR. Arithmetic in IPIR allows division by an interval that contains zero also. This results in closed intervals of real numbers which, however, are no longer bounded. The union of the set IIR with these new intervals is denoted by (IIR). The paper shows that arithmetic operations can be extended to all elements of the set (IIR). On the computer, arithmetic in (IIR) is approximated by arithmetic in the subset (IF ) of closed intervals over the floating-point numbers F ⊂ IR. The usual exceptions of floating-point arithmetic like underflow, overflow, division by zero, or invalid operation do not occur in (IF ).