From pycyn@aol.com Sat Dec 01 16:35:14 2001 Return-Path: X-Sender: Pycyn@aol.com X-Apparently-To: lojban@yahoogroups.com Received: (EGP: mail-8_0_0_1); 2 Dec 2001 00:35:14 -0000 Received: (qmail 14244 invoked from network); 2 Dec 2001 00:35:14 -0000 Received: from unknown (216.115.97.172) by m3.grp.snv.yahoo.com with QMQP; 2 Dec 2001 00:35:14 -0000 Received: from unknown (HELO imo-r03.mx.aol.com) (152.163.225.99) by mta2.grp.snv.yahoo.com with SMTP; 2 Dec 2001 00:35:14 -0000 Received: from Pycyn@aol.com by imo-r03.mx.aol.com (mail_out_v31_r1.9.) id r.11c.8750013 (18710) for ; Sat, 1 Dec 2001 19:35:02 -0500 (EST) Message-ID: <11c.8750013.293ad13c@aol.com> Date: Sat, 1 Dec 2001 19:35:08 EST Subject: Re: [lojban] if To: lojban@yahoogroups.com MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_11c.8750013.293ad13c_boundary" X-Mailer: AOL 7.0 for Windows US sub 118 From: pycyn@aol.com X-Yahoo-Profile: kaliputra --part1_11c.8750013.293ad13c_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 12/1/2001 1:23:00 PM Central Standard Time, ragnarok@pobox.com writes: > My question is, how do you do if-then-else constructions? > Since "if P then Q, else R", assuming that Q and R are meant to be exclusive of one another, involves making all or none of P, Q, ~R true, Refgram says at 14.7 (342) that no combination of Lojban connectives can produce this without repeating at least one sentence. The most natural, then is (P iff Q) and (~P iff R): ga go P gi Q gi gonai P gi R. My memory (usual caveats) is that someone once proposed a single connective for this and that there is a way of dealing with it involving sets of statements, but I forget details on both. (If P and Q are not exclusive, the "iff" can be reduced to "only if" and there might be a simpler form -- there is a chart somewhere in some archive of what can and can't be done with three sentences and two connectives (plus various negations).) --part1_11c.8750013.293ad13c_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 12/1/2001 1:23:00 PM Central Standard Time, ragnarok@pobox.com writes:


My question is, how do you do if-then-else constructions?

Since "if P then Q, else R", assuming that Q and R are meant to be exclusive of one another, involves making all or none of P, Q, ~R true, Refgram says at 14.7 (342) that no combination of Lojban connectives can produce this without repeating at least one sentence.  The most natural, then is (P iff Q) and (~P iff R): ga go P gi Q gi gonai P gi R.  My memory (usual caveats) is that someone once proposed a single connective for this and that there is a way of dealing with it involving sets of statements, but I forget details on both.  (If P and Q are not exclusive, the "iff" can be reduced to "only if" and there might be a simpler form -- there is a chart somewhere in some archive of what can and can't be done with three sentences and two connectives (plus various negations).) --part1_11c.8750013.293ad13c_boundary--