CSE 463/563, Spring 2005
Rules for "Send" and "Return"
Last Update: 14 February 2005
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Here are the details of how the rules of SEND and RETURN work in the
system of propositional logic that we are using.
Note that you may begin (or "call", or "enter"--choose your favorite
metaphor) a subproof only if you are applying ¬INTRO, ¬ELIM, or
We justify information legitimately flowing into a subproof with
the rule SEND plus the citation of the earlier line number outside of the
subproof. The justification SEND can be used, provided:
- We are in a subproof with more asterisks (*) than the cited line.
- The sentence being "sent" is exactly the sentence in the cited
- Every line between the SEND line and the cited line has at least as
many asterisks as the cited line.
We justify information legitimately flowing out of a subproof with
the rule RETURN plus the citation of a line in the subproof. The
justification RETURN can be used, provided:
Schagrin, Morton L.;
Rapaport, William J.; &
Logic: A Computer Approach (New York: McGraw-Hill)
- We are outside of the subproof, with one less asterisk than the cited
- The sentence being returned is exactly the sentence in the cited
- There is no line between the present line and the cited line with
fewer asterisks than the cited line.
- The cited line has the justification ¬INTRO, ¬ELIM, or
- SCI/ENGR Book Collection BC138 .S32 198
Copyright © 2005 by
William J. Rapaport