[isabelle-dev] HOL iff notation

Makarius makarius at sketis.net
Mon Sep 2 16:24:10 CEST 2013

(This is just a side-track on HOL notation, which came to me when cleaning 
up theories with old ASCII replacement syntax like & | --> <-> Un Int etc. 
-- which is very easy with explicit C+b completion in Isabelle/jEdit.)

Isabelle/4379d46c8e13 (Oct 2005) introduces "alternative iff syntax for 
equality on booleans, with print_mode 'iff'".

I can't remember a particular reason for the print mode, instead of having 
that syntax always on. I find myself using the "iff" notation most of the 
time to make theories look "nice".

Are there clubs of "iff" vs. "non-iff"?  If almost everybody is a member 
of the "iff" club we could just remove that print mode.  (We don't have to 
consider that for the coming release, to avoid any real-time pressure on 
this question.)


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