[isabelle-dev] Considered harmful: surj

Florian Haftmann florian at haftmann-online.de
Sat Jul 2 21:08:40 CEST 2016

Hi all,
since cf26dd7395e4, ‹surj f› is a mere abbreviation for ‹range f =
UNIV›. This is a little bit unfortunate since an ordinary equation is
just hidden in output that way, resulting in lots of casual confusion. I
would suggest to turn ‹surj› into a mere input abbreviation, similar to
‹trivial_limit› which also covers an equality. This may also open the
possibility to re-introduce ‹surj_on f A› as in input abbreviation for
‹range f = A›, which got abolished in cf26dd7395e4, leaving a strange
assymmetry wrt. inj(_on), bij(_betw).


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