A Stream Calculus of Bottomed Sequences for Real Number Computation

  • Authors:
  • Kei Terayama;Hideki Tsuiki

  • Affiliations:
  • -;-

  • Venue:
  • Electronic Notes in Theoretical Computer Science (ENTCS)
  • Year:
  • 2013

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Abstract

A calculus XPCF of 1@?-sequences, which are infinite sequences of {0,1,@?} with at most one copy of bottom, is proposed and investigated. It has applications in real number computation in that the unit interval I is topologically embedded in the set @S"@?","1^@w of 1@?-sequences and a real function on I can be written as a program which inputs and outputs 1@?-sequences. In XPCF, one defines a function on @S"@?","1^@w only by specifying its behaviors for the cases that the first digit is 0 and 1. Then, its value for a sequence starting with a bottom is calculated by taking the meet of the values for the sequences obtained by filling the bottom with 0 and 1. The validity of the reduction rule of this calculus is justified by the adequacy theorem to a domain-theoretic semantics. Some example programs including addition and multiplication are shown. Expressive powers of XPCF and related languages are also investigated.